Carrier Type Research Articles

Chemical looping of synthetic ilmenite, Part I: Addressing challenges of kinetic TGA measurements with H[formula omitted]

Reliable experimental data and models are required to better understand and design chemical looping processes with oxygen carrier materials like ilmenite. A dubious variability of suggested kinetics for similar oxygen carrier materials has been presented in the literature. Part I of this work focuses on thermogravimetric analysis (TGA) of gas–solid kinetics and addresses several of its challenges, which are possible reasons behind such deviations. The reduction of synthetic ilmenite (60 mass% Fe2O3＋40 mass% TiO2) powder with H2 in a TGA system was investigated for this purpose.Multiple steps were necessary to overcome mass transfer limitations during the measurements: (i) small sample masses down to 1.6mg, (ii) high gas flow rates, (iii) a suitable sample carrier and (iv) proper sample dispersion on the sample carrier. Three types of sample carriers (crucible, basket and plate) were tested; the plate showed the best performance overall. It was alarming that an exemplary increase in sample mass from 1.6 to 3mg, which was still significantly lower than all other studies reviewed, already introduced a noticeable influence of diffusion. Isothermal (650–950°C, 17–50vol% H2) and nonisothermal parameter studies were conducted and yielded vastly different isoconversional activation energies. A computational fluid dynamics (CFD) study of the TGA system suggested considerable axial dispersion of H2 influencing the initial conversion period.These findings help to assess the reliability of kinetic studies and guide towards diffusion-free, kinetic measurements. The results will be used for model development in part II.

Unconventional magnetotransport properties of two-dimensional ferromagnet Fe5GeTe2

Two-dimensional (2D) van der Waals FexGeTe2 metallic ferromagnets have Curie temperature near or even higher than room temperature, showing great prospects in the field of spintronics. Here, we study the magnetotransport properties of Fe5GeTe2 nanoflakes. Multiple sign changes of angle-dependent magnetoresistance (ADMR) are observed with changing temperature or magnetic field. The high field-induced negative to positive MR transition in low temperatures (T < 50 K) and the temperature-induced sign reversal of anisotropic MR at T = 130 K are responsible for these exotic and complex characteristics of ADMR. In addition, the electron–magnon scattering induced negative MR exhibits abnormal nonmonotonic temperature dependence, which is related to the nonmonotonic variation of anomalous Hall resistance and the transition of the carrier types at T = 150 K. The exotic magnetotransport properties of Fe5GeTe2 revealed in this work may help pave the way for the practical application of this 2D magnetic material.

Anammox process in anaerobic baffled biofilm reactors with columnar packings: Characteristics of flow field and microbial community

The enrichment of anammox bacteria is a key issue in the application of anammox processes. A new type of reactor － anaerobic baffle biofilm reactor (ABBR) developed from anaerobic baffle reactor (ABR) was filled with columnar packings and established for effective enrichment of anammox bacteria. The flow field analysis showed that, compared with ABR, ABBR narrowed the dead zone so as to improve the substrate transferring performances. Two ABBRs with different types of columnar packings (Packings 1 and Packings 2) were constructed to culture anammox biofilms. Packings 1 consisted of the single-form honeycomb carriers while Packings 2 was modular composite packings consisting of non-woven fabric and honeycomb carriers. The effects of different types of columnar packings on microbial community and nitrogen removal were studied. The ABBR filled with Packings 2 had a higher retention rate of biomass than the ABBR filled with Packings 1, making the anammox start-up period be shortened by 21.28%. The enrichment of anammox bacteria were achieved and the dominant anammox bacteria were Candidatus Brocadia in both R1 and R2. However, there were four genera of anammox bacteria in R2 and one genus of anammox bacteria in R1, and the cell density of anammox bacteria in R2 was 95% higher than that in R1. R2 has the advantage of maintaining excellent and stable nitrogen removal performance at high nitrogen loading rate. The results revealed that the packings composed of two types of carriers may have a better enrichment effect on anammox bacteria. This study is of great significance for the rapid enrichment of anammox bacteria and the technical promotion of anammox process.

Исследование зависимости физико-химических свойств флуоресцентных гибридных полимерных носителей от условий гидротермального синтеза

Currently, the search for new types of carriers for low-molecular weight substances, as well as the development of optimal methods for the effective encapsulation of these substances are important tasks of modern chemistry and pharmacology. However, there are still limitations in this area, among which one of the most significant is the lack of the optimal carrier capable of stably retaining a low-molecular weight substance. The work presents hybrid polymer structures obtained by in situ hydrothermal synthesis as an effective candidate for these purposes. The fluorescent dye rhodamine B has been used as a model low-molecular weight substance for encapsulation into the structures. The resulting hybrid polymer structures demonstrated good stability when stored in an aqueous environment for 336 h with the release of the low-molecular weight dye rhodamine B no more than 2%. In addition, the influence of the conditions for obtaining hybrid carriers (including the composition of the carriers (thickness of the polymer shell and the presence of a calcium carbonate core) and synthesis temperature) on their physical-chemical characteristics has been studied. Thus, the optimal approach for obtaining fluorescent hybrid polymer carriers with a set of desired properties has been revealed. In particular, it has been shown that the optimal production conditions are hydrothermal synthesis temperature of 180 °C and the absence of CaCO 3 core inside the polyelectrolyte shell which allow us to obtain a stable hybrid polymer carrier with bright fluorescence. The results presented in this study can be used to create functional platforms and systems with tunable fluorescent properties and the ability to deliver low-molecular weight substances.

Operating temperature and ruthenium doping influence on the charge carriers type transition in the ɑ-Fe2O3 sensors upon liquefied petroleum gases detection

Metal oxide-based sensors have been extensively used for environmental monitoring, health, and safety. This work focuses on synthesizing ɑ-Fe2O3 and doping it with Ruthenium (Ru) to study its gas-sensing properties over flammable and hazardous gases. An anomalous behavior was observed during the Liquefied Petroleum Gas (LPG). This Ru-doped ɑ-Fe2O3 showed a charge carrier switching transition from n- to p-type conductivity due to Ru doping and the sensor’s operating temperature. The switching behavior on the Ru-doped samples happened between 3,000 and 4,000 ppm of the LPG concentrations. However, the Ru doping content did not seem to be affecting this transition except to alter the LPG response. The sensors’ operating temperature did alter the switching transition from n- to p-type conductivity. The temperatures varied from 175 to 225 °C. Metal Oxide Semiconductor (MOS) based on α -Fe2O3 nanoparticle doped with ruthenium (Ru- α-Fe2O3) was more selective towards LPG with a gas response of 24.41.

Correlation between morphology and transport properties of Au/Co/Au/Si wedge ultra-thin film

We report the thermoelectric power (TEP) and electrical resistivity characterization supported by structural and surface morphological properties on a wedge shaped ultra-thin sample of Au/Co/Au/Si (100) with Co have varying thickness from 0.5 nm to 4 nm across the sample. The sample was prepared by Ion Beam Sputtering method, with an ultrathin layer of Co sandwiched between two layers of Au (3 nm thicknesses each). The observed TEP results showed that the system is semiconductor in nature and the concentration of the charge carrier is inversely proportional to the Seebeck coefficient (S) and also concentration of charge carrier modifies with the film thickness leading to a change in thermo power, which is found to be higher at lower thicknesses of Co sandwiched layer. The type of charge carrier was also determined to be electrons in this system. The observed results are in good agreement with the resistivity measurement carried out as a function of film thickness indicating a decrease in resistivity as a function of film thickness due to enhancement in charge carrier mobility. The thermal activation energy was seen to increase from ∼29.5 meV to ∼280.3 meV as the film thickness increased from the minimum to the highest. Corresponding Atomic Force Microscopy (AFM) measurement revealed island type grain growth with the introduction of a significant amount of roughness, while Magnetic Force Microscopy (MFM) experiments exhibit randomly oriented magnetic domain structures. The overall results suggest that lowest thickness film shows semiconducting nature, while variable range hopping phenomena due to some localized energy levels near the valence and conduction band is observed in the highest thickness film. This result is also well supported by XRD measurement, which revealed crystalline nature of the films. Such low cost, easy to fabricate materials may find applications in Peltier cooling or energy harvesting applications without the harmful carbon dioxide emission. For this, advance experiments will be done in future.

‘Where have you been hiding this voice?’

Abstract This study explores compliments given by judges to contestants on the TV talent show Arab Idol. A total of 120 comments from the third season 2014–2015 were analyzed for compliment types, structures, lexicon, and supportive remarks. Spenser-Oatey’s (2000, 2002, 2005a, 2005b, 2008) rapport management theory was employed to determine how judges managed rapport with contestants through compliments. The analysis shows that the majority of judges’ compliments on the show were explicit compliments that were based on three syntactic patterns and four types of positive semantic carriers conveying complimenting adjectives, verbs, nouns, and adverbs. A smaller category of implicit compliments involved such strategies as comparison/contrast, rhetorical questions, and praising contestant’s country. Both categories were typically qualified by supportive or weakening elements such as repetition, encouragement, and criticism, resulting in a third category of ‘macro-compliments’. The study shows that rapport management accounts to a large extent for the judges’ complimenting behavior.

Effective nitrogen removal from onsite wastewater using a sequencing aerated biofilm reactor

A novel sequencing aerated biofilm reactor (SABR) was designed for effective nitrogen removal from onsite wastewater with a footprint 10 times smaller than conventional drainfield and a high hydraulic capacity. The study examined the effect of aeration pattern, wastewater strength, and carrier type on N-removal performance. Over 93 % COD removal and > 80 % TN-removal was achieved in the SABR integrated with a polishing unit (10 % woodchips, v/v) at the optimized aeration pattern (4-h pre-anoxic, 7 aeration cycles of 20 min aeration per hour at 1 L-air/min airflow rate, 1 h post-anoxic). Carriers' shape and surface area did not impact SABR's N-removal performance (31.8 % vs. 28.2 %). The optimal operation conditions obtained in bench-scale SABR tests were pilot tested with the 10 % woodchip polishing unit. Efficient TN-removal (72.4 %) was achieved with low effluent TN concentrations (6.5 ± 3.9 mg-N/L) by the pilot SABR. Ammonium (NH4+) was the predominant N-species (5.5 ± 6.0 mg-N/L) in the final effluent while NOx− was constantly below the detection limit (< 0.05 mg-N/L). Quantitative PCR analysis of functional genes involved in N-removal (amoA-AOA, amoA-AOB, nirS, nirK and nosZ) were comparable for bench-scale and pilot-scale SABRs and revealed higher abundance of amoA-AOB (> 4 orders of magnitudes higher than amoA-AOA) and nirS (nirK/nirS: 0.2–1.8 × 10−2), suggesting amoA-AOB and nirS may serve as biomarkers to monitor the system performance. Collectively, the results suggest that SABR offers a versatile approach to treat wastewater at various strengths and is applicable in areas with space constraints, shallow groundwater, and sensitive water bodies.

Ternary solid dispersions of lacidipine: Enhancing dissolution and supersaturation maintenance through strategic formulation optimization

The study aimed to address the challenges related to insufficient dissolution and maintenance of supersaturation in binary solid dispersions. Lacidipine, categorized as a BCS class II drug, was employed as the model drug. A systematic screening of excipients was conducted to determine the most effective carriers for the formulations of the ternary solid dispersions, utilizing the solvent transfer method and equilibrium solubility measurements. Both binary and ternary solid dispersions were prepared via spray drying, and comprehensive physicochemical characterization confirmed the successful preparation of amorphous solid dispersions. In vitro dissolution tests, the ternary solid dispersion exhibited marked superiority over the binary solid dispersion in dissolution and maintenance of supersaturation. Furthermore, an exploration into the factors influencing the stability of ternary solid dispersions revealed their robust resistance under light-protected, room-temperature, and desiccated conditions. The formation of intermolecular hydrogen bonding within the molecules of the ternary solid dispersions significantly enhanced drug solubility and system stability. Strategic formulation optimization, coupled with judicious selection of suitable carrier types and ratios, may serve as a promising approach for designing supersaturated drug delivery systems.

Stability and Electronic Structure of Nitrogen-Doped Graphene-Supported Cun (n = 1-5) Clusters in Vacuum and under Electrochemical Conditions: Toward Sensor and Catalyst Design.

Here, we present a detailed computational study of the stability and the electronic structure of nitrogen-doped graphene (N4V2) supported Cun (n = 1-5) clusters, which are promising carbon-dioxide electroreduction catalysts. The binding of the clusters to the nitrogen-doped graphene and the electronic structure of these systems were investigated under vacuum and electrochemical conditions. The stability analysis showed that among the systems, the nitrogen-doped graphene bound Cu4 is the most stable in vacuum, while in an electrolyte, and at a negative potential, the N4V2-Cu3 is energetically more favorable. The ground state electronic structure of the nitrogen-doped graphene substrate undergoes topological phase transition, from a semimetallic state, and we observed a metallic and topologically trivial state after the clusters are deposited. The electrode potential adjusts the type and density of the charge carriers in the semimetallic models, while the structures containing copper exhibit bands which are deformed and relaxed by the modified number of electrons.

Point Defect Limited Carrier Mobility in 2D Transition Metal Dichalcogenides.

2D transition metal dichalcogenide (MX2) semiconductors are promising candidates for electronic and optoelectronic applications. However, they have relatively low charge carrier mobility at room temperature. Defects are important scattering sources, while their quantitative roles remain unclear. Here we employ first-principles methods to accurately calculate the scatterings by different types of defects (chalcogen vacancies, antisites, and oxygen substitutes) and the resulting carrier mobilities for various MX2 (M = Mo/W and X = S/Se). We find that for the same X, WX2 always has a higher mobility than MoX2, regardless of defect type and carrier type. Further analyses attribute this to the universally weaker electron-defect coupling in WX2. Moreover, we find filling the chalcogen vacancy with O always improves the mobility, while filling by a metal atom decreases the mobility except for WSe2. Finally, we identify the critical defect concentrations where the defect- and phonon-limited mobilities cross, providing guidelines for experimental optimization.

Regulating the dopant clustering in LiZnAs-based diluted magnetic semiconductor

Tuning of the magnetic interaction plays the vital role in reducing the clustering of magnetic dopant in diluted magnetic semiconductors (DMS). Due to the not well understood magnetic mechanism and the interplay between different magnetic mechanisms, no efficient and universal tuning strategy is proposed at present. Here, the magnetic interactions and formation energies of isovalent-doped (Mn) and aliovalent (Cr)-doped LiZnAs are studied based on density functional theory (DFT). It is found that the dopant–dopant distance-dependent magnetic interaction is highly sensitive to the carrier concentration and carrier type and can only be explained by the interplay between two magnetic mechanisms, i.e., super-exchange and Zener’s p–d exchange model. Thus, the magnetic behavior and clustering of magnetic dopant can be tuned by the interplay between two magnetic mechanisms. The insensitivity of the tuning effect to U parameter suggests that our strategy could be universal to other DMS.

Transport properties and electronic phase transitions in two-dimensional tellurium at high pressure

Utilizing in situ Raman spectroscopy, resistivity, and Hall-effect measurements, we conducted an extensive investigation on the continuous electronic phase transitions and transport properties of two-dimensional (2D) tellurium (Te) under high pressure at room and low temperature (80–300 K). The distinguishable decrease in the A1 Raman mode's full width at half maximum in the trigonal phase (Te-I) indicated an electronic phase transition at 2.2 GPa. The following Hall-effect experiments located the Lifshitz transition and the semiconductor-semimetal transition at 0.9 and 1.9 GPa, respectively, and the semiconductor-semimetal transition was also confirmed by resistivity variation through temperature. The charge carrier types of the Te changed from hole to electron during the phase transition from Te-I to Te-II (triclinic phase) at low temperature, while the transport parameters remained almost unchanged during the phase transition from Te-II to Te-III (monoclinic phase). The results offered complete and thorough electronic phase transitions and transport characteristics of 2D Te, hence great advancing the potential application of Te in electronic devices.

Optical-pump-terahertz-probe spectroscopy in high magnetic fields with kHz single-shot detection.

We demonstrate optical pump-THz probe (OPTP) spectroscopy with a variable external magnetic field (0-9T), in which the time-dependent THz signal is measured by echelon-based single-shot detection at a repetition rate of 1kHz. The method reduces data acquisition times by more than an order of magnitude compared to conventional electro-optic sampling using a scanning delay stage. The approach illustrates the wide applicability of the single-shot measurement approach to non-equilibrium systems that are studied through OPTP spectroscopy, especially in cases where parameters such as magnetic field strength (B) or other experimental parameters are varied. We demonstrate the capabilities of our measurement by performing cyclotron resonance experiments in bulk silicon, where we observe B-field-dependent carrier relaxation and distinct relaxation rates for different carrier types. We use a pair of economical linear array detectors to measure 500 time points on each shot, offering an equivalent performance to camera-based detection with possibilities for higher repetition rates.

Men at Work…Unsafely: Gender Differences in Compliance with Safety Regulations in the Trucking Industry

Although safety within operational systems depends on compliance with regulations, non-compliance is common in many settings. Trucking is a meaningful industry for studying operational safety compliance given that the industry is large and important, truck accidents kill thousands annually, and such accidents collectively cost the U.S. economy billions of dollars. Although the truck driving occupation is dominated by men, significant efforts are underway to recruit more women into the profession. If women are safer behind the wheel than men, increasing their ranks could improve overall safety compliance. Building on theory and evidence suggesting that men have a greater willingness to take risky actions and break rules, we used data on 22 million truck inspections from 2010 to 2022 to identify an operational safety compliance gap between men and women truckers. Overall, men were 7.4% more likely to be cited for a major violation of rules governing working hours (known as hours-of-service or HOS rules) and 13.2% more likely to have a major unsafe driving violation. We then examined whether gap changes based on carrier size and type. We found that the HOS compliance gap is smaller for small carriers (vs. large) and private carriers (vs. for-hire), but not the unsafe driving gap. Finally, we tested whether the introduction of an intervention—electronic logging devices (ELDs) that automatically record truckers’ driving hours—closes the gap by increasing men's compliance. In line with predictions, differences between men and women disappeared after the mandate; but again, only for HOS compliance. Surprisingly, women had significantly more HOS violations in 2021 and 2022 than men—an outcome that may be tied to women truckers’ personal safety issues. In summary, the results and additional robustness checks indicate that men committed more unsafe driving violations (e.g., speeding) than women across the entire study period, while the pattern of HOS violations varied based on external events. We conclude by highlighting possible pathways for reducing the number of collisions involving trucks and thus lowering the number of fatalities and extent of economic losses.

Impact of social determinants of health on follow-up adherence, testing completion, and outcomes among pediatric glaucoma patients at a tertiary care center

PurposeTo identify patient characteristics associated with visit attendance, treatment outcomes, and optical coherence tomography (OCT) testing in pediatric glaucoma patients at an urban tertiary care center. MethodsThe records of patients with childhood glaucoma seen from 2015 to 2021 were reviewed. Primary outcomes were the proportion of scheduled visits completed, visual acuity and intraocular pressure (IOP) at most recent follow-up, and rates of OCT testing. Social determinants of health evaluated included race and ethnicity, distance of residence from clinic, insurance carrier type and residence within Baltimore City County, the latter two serving as proxies for socioeconomic status. ResultsA total of 99 patients met inclusion criteria: 61% were male; 47%, white (non-Hispanic); 25%, black (non-Hispanic); 11%, Hispanic/Latino; and 7% Asian/Pacific Islander. Mean distance from clinic was 45.3 miles. Mean visit completion rate was 90.4%; there was no statistically significant variation in visit completion rates by patient characteristics. IOP outcomes did not vary across patient groups, but visual acuity outcomes in affected eyes were significantly worse among Baltimore City County residents compared with non-residents. Only 22% of the cohort received ≥1 OCT per year, and patients living 0-29.9 miles from clinic had significantly lower odds of reaching the threshold than more distant patients. Patients with state-based insurance had significantly lower odds of being ≥50th percentile for rate of OCTs received compared to patients with commercial insurance. ConclusionsIn children with glaucoma, residence within Baltimore City County was associated with significantly worse visual acuity outcomes, and close proximity to clinic was an independent predictor of lower rates of OCT testing, despite similar visit attendance rates and IOP outcomes across all groups.

Effect of Carrier Materials for Active Silver in Antibacterial Powder Coatings

Environmentally friendly powder coatings which have the advantages of being VOC-free, low-cost, and high-efficiency with a high recovery rate have been attracting increasing research attention. The introduction of antibacterial agents into the powder coatings endows them with a capacity to kill bacteria and viruses on the surface of objects; additionally, this enables them to inhibit the indirect transmission of pathogenic microorganisms. Silver, possessing broad-spectrum, strong, and stable antibacterial properties, is considered to be a promising antibacterial material for use in coating applications. Carrier materials for active silver play an important role in its activity and stability. However, there is a lack of systematic studies on the effects of different types of carriers in such coating systems, especially in green powder coating systems. In this paper, we investigated two types of carriers for active silver agents: zeolite, i.e., Linde type A (LTA) zeolite and Y-type zeolite; clay-based materials, i.e., montmorillonite and vermiculite. All the agents showed high antibacterial activity, with antibacterial rates of over 99% as compared to commercial agents. Among the four agents, the Ag-LTA zeolite antimicrobial agent showed a reduction rate of over 99.99%; additionally, it maintained a reduction rate of 99% after seven washing cycles. Thus, this agent was demonstrated to have the highest effectiveness and high durability; these features can be attributed to the high silver content and small particle size. The LTA zeolite also provides a protective effect for silver ions, protecting them from reduction, due to the restriction of elemental silver formation within the confined interior space of the α-cage structure. The Y-type zeolite antimicrobial agent exhibited a slightly lower antimicrobial performance due to its higher silicon-to-aluminum ratio and its lower cation exchange capacity. Comparatively, antimicrobial agents utilizing clay-based carriers have lower cation exchange capacity, resulting in poorer antimicrobial effectiveness than zeolite carriers. In addition, silver loaded on clay-based materials is prone to detach from the carrier and undergo a reduction reaction, making the coating yellowish in color. This study first provides information on the roles of different types of carriers in powder coating systems; then, this information guides the selection of carriers for active silver for the development of efficient antimicrobial agents and coatings.

Suppression of plasmonic interference in helicity sensitive broadband terahertz detectors

The recently observed helicity-sensitive response, occurring in graphene based field-effect transistors (FETs) is interpreted as a result of the intrinsic phase asymmetry of these devices and interference of plasmons in the FET channel. The graphene-based plasmonic interferometers presented in this work enable the room temperature detection of THz radiation as well as allows us to distinguish between the rotation direction of circular polarized waves. To illustrate the broadband nurture of the observed effects, similar measurements were carried out at both THz and mid-infrared frequencies. The precise control of the carriers type and their concentration throughout the channel length allows us to demonstrate the helicity-sensitive response over a wide range of the gate potentials (from negative to positive values). We experimentally show that the formation of p–n junction inside the graphene channel leads to additional scattering of excited plasma waves, resulting in the suppression of their interference and consequent reduction of the helicity-sensitive contribution.

Effect of catalyst carrier type and concentration on oxygen-scavenging property and characteristics of iron-based active films.

The online version contains supplementary material available at 10.1007/s10068-024-01520-4.

Removal of High Concentrations of Arsenite from Aqueous Solutions by the Emulsion Liquid Membrane Technique

AbstractAs(III) is a dangerous species that contaminates groundwater resources and therefore water purification from this element is necessary. In this study, the removal of As(III) was investigated by the emulsion liquid membrane (ELM) technique due to the high toxicity levels of this species. The effect of various parameters such as hydrochloric acid and arsenic concentration in the feed solution, emulsion to feed ratio, surfactant concentration and type of carrier was evaluated on the arsenic separation efficiency. The results showed that the best type of carrier in terms of emulsion stability and separation efficiency of arsenic ions was di‐(2‐ethylhexyl) phosphoric acid (D2EHPA), and its optimal concentration was about 5 % (v/v). In addition, paraffin as the organic solvent performed better than the mixture of paraffin and kerosene in the separation of As(III) ions. The optimal conditions were obtained at 8 and 0.1 M HCl concentrations for the feed and the internal phases, respectively. Also, the emulsion to feed ratio of 1 : 4.5, the volume ratio of the internal phase to the membrane phase of 1 : 1 and the surfactant concentration of 5 % (v/v) led to achieving the maximum removal of arsenic ions. This work presents a broad perspective of removing As(III) ions from wastewater by carefully examining the parameters influencing the separation of this hazardous element through the ELM method.