Mass Transfer Path Research Articles

Geometry effect on the mass transfer of slug flow in the microchannels with periodic expansion units

Although it was experimentally verified the microchannels with periodic expansion structures can effectively intensify the mass transfer of the slug flow, little research has focused on their geometric design. Hereon, a numerical simulation is conducted to evaluate the impact of microchannel geometry on the mass transfer of slug flow. The square expansion unit performs better than the triangular and circular ones. With the increase of the length, width, and number of the expansion units, and the width of the constriction between the adjacent expansions, the mass transfer performance shows a non-monotonic variation, that is an initial increase followed by a decrease. The underlying reasons are analyzed by evaluating the mixing inside and outside the droplet and the effective mass transfer area. At the preliminarily optimized geometry, a novel mass transfer path, in which not only the droplet caps but also the droplet body becomes the effective mass transfer area, is observed.

Understanding the Effect of Applied Current and Potential on Pitting in 316L Stainless Steels

Abstract The pit morphologies of Type 316L stainless steel were evaluated with ‘sandwiched’ foil electrodes to identify pit growth characteristics under galvanostatic and potentiostatic polarization through ex situ and in situ tests. The applied current and potential values influenced the pit morphologies and lacy cover formation. A direct correlation was found between the type of lacy cover and the observed pit morphologies. The fastest pit depth growth occurred with only one opening on the lacy cover due to ‘pit dissolution induced convection’, while the shortest mass transfer path led to faster lateral pit growth with a perforated lacy cover or open pit.

Facile synthesis of ultrafine RuTe2 nanoparticles supported on B, N co-doped graphene as an efficient HER catalyst

Recently, ruthenium telluride (RuTe2) has received widespread attention as an effective HER catalyst. In this work, ultrafine and well-dispersed RuTe2 nanoparticles anchored on nitrogen and boron co-doped graphene (RuTe2/BNG) was developed by freeze-drying and facile pyrolysis method, demonstrating a brilliant HER performance. The overpotential of RuTe2/BNG at the current density of 10 mA cm−2 is only 34 and 16 mV in 0.5 M H2SO4 and 1.0 M KOH solution, respectively. More importantly, the RuTe2/BNG can also maintain significantly robust HER stability during long-term chronopotentiometry measurements. The outstanding HER activity of RuTe2/BNG should be ascribed to its properties with abundant defects, large specific surface area, high electronic conductivity and short mass transfer path. Our work offers a new path to fabricate efficient HER catalysts by homogeneously anchoring RuTe2 on B, N co-doped graphene.

Nonadditivity and Nonlinearity of Mobile and Stationary Zone Mass Transfer Resistances in Chromatography.

Using a two-zone moment analysis (TZMA) method based on Brenner's generalized dispersion theory for two-dimensional (2D) and three-dimensional (3D) periodic media, we investigated the mechanisms for dispersion in particulate media for liquid chromatography. This was done using a set of plate height data covering an unprecedented wide range of retention factors, diffusion coefficients, and velocities, all computed with unequaled accuracy. Applying Giddings' additivity test, based on alternatingly making the diffusion coefficient in the mobile and stationary zones infinitely large, the dispersion data clearly indicate a lack of additivity. Although this lack could be directly understood by identifying the existence of multiple parallel mass transfer paths, the additivity assumption interestingly overestimates the true C term band broadening (typically by more than 10%, depending on conditions and dimensionality of the system). However, Giddings originally asserted the occurrence of parallel paths would always lead to an underestimation of the dispersion. The origin of the lack of additivity is analyzed in detail and qualitatively explained. Finally, we also established a generic framework for the modeling of the effect of the reduced velocity and the retention coefficient on the C term in ordered chromatographic media. This led to the introduction of a new expression for the mobile zone mass transfer term, which, unlike the currently used literature expression, contains the complete k″ dependency.

Effect of B on the microstructure and mechanical properties of Cu–Cu joints with in-situ Ag–Cu–Zn–Sn filler metal

With the development of advanced manufacturing, traditional Ag-based filler metals cannot reconcile the contradiction between high performance and complex processing. It also unable to meet the requirements of new materials, new structures and new processes for brazing connection performance. In this paper, based on the Ag–Cu–Zn–Sn flux-cored filler metal, the effect of the addition of B on the microstructure and mechanical properties of Cu–Cu brazing joints was investigated using FESEM‒EDS, EPMA, EBSD, TEM, microindenter and universal tensile testing machine. The results indicated that the microstructure in the brazing seam was mainly composed of Ag (s.s), Cu(s.s) and (Ag + Cu) eutectic. With increasing B content, the grain size and texture strength of Ag(s) and Cu(s) gradually decreased. The refinement of Ag-rich dendrites was mainly due to the enrichment of B atoms around the dendrite, which limited the diffusion of solute atoms in the melt and the release of solidification latent heat in front of the liquid‒solid interface, further inhibiting the growth of Ag-rich dendrites. The refinement behavior of Cu-rich dendrites was mainly attributed to the increase in B content, which reduced the tip radius of Cu-rich dendrites. The mass transfer path of B → B2O3 and B → liquid CuSn alloy → mixed melt of CuSn alloy + solder skin alloy → liquid filler metal in the brazed joint → Cu rich phase and grain boundary in the brazed joint → Ag rich phase and grain boundary in the brazing seam was clarified. The addition of B can improve the microhardness of the brazing seam. The shear strength reached a maximum value of 237.2 MPa when B was added at 2%. The fracture models mainly included intergranular fracture, dimple fracture and cleavage fracture. The strength of brazed joints can be improved by solid solution strengthening, process hardening strengthening and fine grain strengthening. The tangle and jog of dislocations within the crystal, the presence of a large number of grain boundaries and B-rich areas can prevent crack tip extension and enhance the toughness of brazing joints.

Synthesis of TS-1 encapsulated Pt (Pt@TS-1) catalyst with hierarchical pores and its enhanced performance in the oxidation of toluene

Generally, the distribution, dispersion and size of Pt nanoparticles are critical issues for high catalytic activity. A series of TS-1 encapsulated Pt (xPt@TS-1 x = 1.70, 0.81, 0.22, 0.08) catalysts with hierarchical pores were prepared by one-pot hydrothermal method and alkali etching treatment, and their catalytic performance were also investigated in the oxidation of toluene. The physicochemical properties of these catalysts were analyzed by XRD, TEM, N2 adsorption-desorption, ICP-OES and XPS etc. Among these catalysts, the 0.22Pt@TS-1 sample with very low Pt loading (0.22 wt%) showed good catalytic activity (T50 = 144 °C and T90 = 147 °C under WHSV of 20,000 mL∙h−1 g−1) and high TOF value (3.6 × 10−4 S-1), moreover, it also exhibited good continuous cycle use, long-term activity stability and water resistance. The preparation method can limit the aggregation and growth of Pt nanoparticles to obtain high dispersion of Pt in TS-1, which can enhance the catalytic oxidation of toluene. In addition, the hierarchical pores formed by alkali etching treatment can shorten the mass transfer path and promote the mass transfer diffusion, which is also conducive to the catalytic activity.

A Solid Redox Mediator Analog as a Highly Efficient Catalyst for Na–O2 Batteries

During the discharge of Na–O2 batteries, O2 is reduced and combines with Na+ to form an insulating solid sodium oxide on the cathode, which severely hinders the mass transfer path, resulting in high polarization voltage, low energy efficiency, and short battery life. Hereby, we proposed a novel illumination-assisted Na–O2 battery in which bismuth vanadate (BiVO4) with few defects and high surface areas was used as the catalyst. It showed that the charge overpotential under photo assistance reduced by 1.11 V compared with that of the dark state one. Additionally, the insolating sodium oxide discharge products were completely decomposed, which was the key to running Na–O2 batteries over 200 cycles with a charge potential of no more than 3.65 V, while its counterpart (under dark condition) at 200 cycles had the charge potential higher than 4.25 V. The experiment combined with theoretical calculation shows that few defects, high surface areas, the altered electron transfer kinetics, and the low energy gap and low oxygen absorption energy of the (040) crystal face of monoclinic BiVO4 play an important role in catalyzing oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).

Transport of Zn (Ⅱ) through matrix enhanced polymer inclusion membrane containing OHA and D2EHPA

Recovery of heavy metal ions from waste water has benefits both in terms of resources reuse and environmental protection. Polymer inclusion membrane (PIM) has received increasing attention as a gentle and simple method compared to other separation techniques for the removal and recovery of heavy metal ions. The extractant and matrix are the most important components of the PIM. In this paper, a novel matrix enhanced polymer inclusion membrane (ME-PIM) system containing both octyl hydroxamic acid (OHA) and di (2-ethylhexyl) phosphoric acid (D2EHPA) as the carriers as well as poly(vinyl) chloride (PVC) and poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) as the matrix was reported. The SEM results indicate that the PVC has excellent compatibility with OHA and D2EHPA, resulting in dense ME-PIM compared to PVDF-CTFE. The effects of OHA and D2EHPA with different carrier ratios on the transport and the stability of the membrane were examined using Zn (Ⅱ) as a representative of heavy metal ions. The optimal results of this work showed that the initial mass transfer flux value of Zn (Ⅱ) was as high as 4.73 μmol/(m2·s), corresponding to a permeability of 2.21 × 10−2 m/h, using the ME-PIM composed of 61 wt.% PVC and 22 wt.% OHA + 17 wt.% D2EHPA. All these results suggest that the ME-PIM has a much higher initial mass transfer flux than those of PIMs in literatures. The addition of OHA to PIM introduced extractive functional groups into the polymer chain, forming an efficient and progressive mass transfer path with the extractant D2EHPA. Utilizing two extractants with synergistic effects, this novel ME-PIM system provides a potential advantage in promoting the mass transfer of metal ions in a PIM.

A novel pomegranate-inspired bifunctional electrode materials design for acetylcholinesterase biosensor and methanol oxidation reaction

A pomegranate-inspired bifunctional electrode material based on Ni/NiO nanoparticle embedded in nitrogen-doped, partially graphitized carbon framework (Ni/NiO@NPGC) was designed and prepared for the construction of novel electrochemical biosensor and methanol oxidation reaction (MOR). Profiting from itsspecialstructureandfunction, Ni/NiO@NPGC was employed as a matrix immobilizing acetylcholinesterase (AChE) for methyl parathion (MP) sensor. The developed biosensor was proved to have wide linear range (1.0 × 10-14-1.0 × 10-8 g mL−1), low detection limit (3.5 × 10-15 g mL−1), and good stability for the determination of MP in practical samples. In addition, the Ni/NiO@NPGC electrode exhibited high electrocatalytic activity (specific activity 73.1 mA cm−2) and durability for the MOR in alkaline medium. The results were mainly attributed to the pomegranate-like architecture structure with pyridinic N and carbon frame of Ni/NiO@NPGC, which ensured the electrochemical activities of all nanoparticles and immobilization of enzyme. In addition, the metal oxide was well dispersed to prevent from self-agglomeration and kept mass transfer paths. The work provides a reference for the development of high-performance bifunctional electrode material for the biosensor and MOR.

Increasing the ⋅OH radical concentration synergistically with plasma electrolysis and ultrasound in aqueous DMSO solution

In recent years, significant increases in waste processing and material engineering have been seen by using advanced oxidation processes. The treatment results and energy yields of these processes are largely determined by the generation and retention of reactive oxygen species (ROS). However, increasing the amount of ROS remains a key challenge because of the unavailability of performance- and energy-efficient techniques. In this study, plasma electrolysis, ultrasound, and plasma electrolysis combined with ultrasound were used to treat dimethyl sulfoxide (DMSO) solutions, and the results showed that the two methods can synergistically convert filament discharge into spark discharge, and the conversion of the discharge mode can significantly increase the concentration of OH radicals and effectively improve the efficiency of DMSO degradation. We verified the rationality of the results by analyzing the mass transfer path of ROS based on the reaction coefficients and found that the ⋅OH radicals in aqueous solution were mainly derived from the decomposition of hydrogen peroxide. These findings indicated that the synergistic action of plasma electrolysis and ultrasound can enhance the production of chemically reactive species, and provide new insights and guiding principles for the future translation of this combined strategy into real-life applications. Our results demonstrated that the synergistic strategy of ultrasound and plasma electrolysis is feasible in the switching mode and increasing the ROS, and may open new routes for materials engineering and pollutant degradation.

2-μm fused-core column ultra-high-performance liquid chromatography/tandem mass spectrometric determination of donepezil in human plasma: Application to a bioequivalence study

Ultra-high-performance liquid chromatography (UHPLC) hyphenated to tandem mass spectrometric methods using the dimethylpentafluorophenylpropyl stationary phase with polar and nonpolar characteristics of a 2-μm fused-core silica particle packing were evaluated to perform efficient separation for the analysis of donepezil in human plasma. The fused-core silica particle design providing the shorter diffusional mass transfer path for the analytes is less affected in resolving power by increasing mobile-phase velocity for faster chromatographic resolution between the administered compound and multiple interfering peaks from the extracted quality control, calibration standard and study samples following simple protein precipitation extraction procedures. In this work, two UHPLC-MS/MS approaches requiring 1.2 min per sample run time and neither expensive ultra-high-pressure instrumentation nor new laboratory protocols were applied and compared for determination of donepezil in human plasma at sub-nanograms per milliliter region to support a randomized, crossover bioequivalence (BE) study in which healthy volunteers each received a single oral dose of the test and reference formulations of 10 mg donepezil hydrochloride. The column performance in terms of chromatographic separation efficiency, peak asymmetry and resolution and retention time reproducibility was found to be sustainable over a thousand extracted plasma injections. The linear dynamic range was detected over a concentration range of 0.2–50 ng/mL. The intra- and inter-day assay accuracy and precision were within 15% for the analyte in individual biological fluids. Positive correlation coefficients (r) greater than 0.98 and 0.99 for donepezil concentrations in study plasma samplers measured by the proposed UHPLC-MS/MS approaches and another validated HPLC-MS/MS method were observed.

In-situ synthesis of Co3O4 nanocrystal clusters on graphene as high-performance oxygen reduction reaction electrocatalysts

ABSTRACT The energy problem is closely related to the survival and development of human beings. Nowadays, the research of fuel cells is making rapid progress, but the bottleneck of the development of fuel cells is slow oxygen reduction reaction (ORR) of cathode. At present, it is difficult to develop a kind of oxygen reduction catalyst with high performance, low energy consumption and low pollution. Here, we synthesised Co3O4 nanocrystals loaded on a single graphene oxide layer via a convenient one-step hydrothermal method. According to the transmission electron microscopy characterisation tests, the average size of Co3O4 nanocrystals is 5 nm. Compared with the commercially available Pt/C catalyst, the obtained Co3O4/rGO catalyst demonstrates the same four-electron (4e−) oxygen reduction reaction, and the catalytic activity of ORR is significantly higher. This is due to the large surface area provided by the middle part of the composite catalyst Co3O4/rGO, which provides an effective mass transfer and electron transfer path for the catalyst.

MoS2 nanosheets grown on carbon cloth as a bifunctional cathode for long-life Na–O2 batteries

When sodium (Na)–oxygen (O2) batteries discharge, O2 is reduced on the cathode to form solid sodium oxides deposited on cathode, severely impeding the mass transfer path and causing large voltage polarization, low energy efficiency and poor rate performance. Therefore, a novel cathode is the key to solving the above issues. Here, in-situ growing molybdenum disulfide on carbon cloth (MoS2/CC) as a binder-free cathode is prepared by a simple and facile hydrothermal method. When this cathode is tested in Na–O2 batteries, it presents enhanced oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activity as well as large discharge capacity. What's more, Na–O2 batteries with the MoS2/CC cathode simultaneously produce sodium superoxide (NaO2) and poor crystalline sodium peroxide (Na2O2), which greatly reduces the charge potential.

Effect of nanoparticles on interfacial mass transfer characteristics and mechanisms in liquid-liquid extraction by molecular dynamics simulation

The addition of nanoparticles is a promising strategy to intensify interfacial mass transfer, which possess a wide array of potential applications in considerable industrial processes. In order to elucidate interfacial mass transfer characteristics and mechanisms, the effects of functional group, particle size and volume fraction of silica nanoparticle on dimethyl sulfoxide (DMSO) transfer across the water/hexane interface were investigated by molecular dynamics simulation. The results manifested that hydrophilic nanoparticles are beneficial to mass transfer enhancement. Due to the increase of mass transfer path and steric hindrance of nanoparticles at the liquid-liquid interface, however, hydrophobic and amphiphilic nanoparticles inhibit solute mass transfer. Moreover, the smallest size nanoparticle at the maximum concentration of 10 vol% leads to the highest enhancement, namely the decrease of mass transfer resistance by 36%. By analyzing the mean square displacement and size effect of nanoparticle, it is found that Brownian motion rather than micro-convection is probably the dominant mechanism.

Strategies with Functional Materials in Tackling Instability Challenges of Non-aqueous Lithium-Oxygen Batteries

The instabilities of the battery including cathode corrosion/passivation, shuttling effect of the redox mediators, Li anode corrosion, and electrolyte decomposition are major barriers toward the practical implementation of lithium-oxygen(Li-O2) batteries. Functional materials offer great potential in high performance Li-O2 batteries owing to their functional tailorability of chemical modification for alleviating side reactions and improving catalysis activity, well-defined properties for discharge products storage, and fast mass and electron transfer paths. In this review, instability problems of non-aqueous Li-O2 batteries and recent studies related to the functional materials in tackling the instability issues from rational cathode construction, inhibition of redox mediators(RMs) shuttling, anode protection and novel electrolyte design are illustrated. Future research directions to overcome the critical issues are also proposed for this promising battery technology. The instability issues and the related strategies with functional materials based on the comprehensive consideration of all battery components proposed in this review provide the systematic, deep understanding and rational design of functional materials for Li-O2 batteries, which is beneficial to achieving the practical Li-O2 batteries.

Rapid catalytic hydrolysis performance of Mg alloy enhanced by MoS2 auxiliary mass transfer

Mg10Ni-MoS2 composites were synthesized, and the amount of molybdenum disulfide (MoS2) and ball milling time was optimized to obtain rapid initial kinetics with high conversion yield at room temperature in simulated seawater. The microstructures and H2 generation thermodynamics were comprehensively investigated to demonstrate the main influential factors on excellent initial hydrolysis performance. Mg10Ni-5 wt%MoS2-15 min can generate 493.3 mL·g-1 H2 at 298 K with 58% yield in 20 s. The H2 generation capabilities of Mg10Ni-5 wt% MoS2-15 min are 569 mL·g-1 H2 and 67%, which are higher than those of Mg10Ni (495 mL·g-1 H2, 56%) in 2 min. The lowest hydrolysis activation energy (18.74 kJ·mol-1) can be achieved by Mg10Ni-5 wt%MoS2, which means low energy consumption. Mg10Ni with higher specific surface area (4.04 m2⋅g-1) than that of Mg10Ni-5wt.%MoS2-15 min (0.78 m2⋅g-1) presents worse H2 generation performance, indicating that higher specific surface area is the secondary determinant for superior initial hydrolysis kinetics and higher conversion yield compared with the added MoS2. The added MoS2 with specific morphologic structure can provide auxiliary mass transfer paths, which shorten the transfer distance and destroy the continuous colloidal layer. Mg-rich alloys optimized for rapid and efficient H2 production performance are expected to be applied large-scale H2 generators.

Porous and ultrafine nitrogen-doped carbon nanofibers from bacterial cellulose with superior adsorption capacity for adsorption removal of low-concentration 4-chlorophenol

Porous and Ultrafine Nitrogen-doped carbon nanofibers (NCNFs) were successfully obtained from bacterial cellulose (BC) by carbonization/activation in NH3/N2 atmosphere at higher temperatures. Thanks to the ammonia treatment, the as-obtained NCNFs have nanoarchitectures constructed of one-dimensional (1-D) nanofiber with ultrafine fibers, hierarchically porous structures, abundant nitrogen functionalities leading to the basic and hydrophobic surface, which render them as excellent adsorbents for the adsorption removal of organic pollutants from aqueous solutions. Their adsorption performance for low-concentration 4-chlorophenol (4-CP) were investigated systematically under different conditions. In comparison with the carbon nanofibers (CNFs) without ammonia treatment and commercial activated carbon (CAC), NCNFs displayed greatly enhanced adsorption capacity, short equilibrium time and wide pH range. NCNF-1000 prepared at 1000 °C had adsorption capacity of 4-CP up to 604.1 mg/g for the initial low-concentration of 100 mg/L, which was superior to the previously reported adsorbents. Analyses of the equilibrium adsorption and kinetic data revealed that the adsorption process of 4-CP onto NCNFs were fitted well with the Liu isotherm and pseudo-second-order kinetic models. The thermodynamic parameters (ΔH°, ΔS°, ΔG°) for 4-CP adsorption onto NCNFs confirmed that the essence of 4-CP adsorption was exothermic, feasible and spontaneous. The possible adsorption mechanism of 4-CP on NCNFs was proposed. The excellent adsorption performance of NCNFs for 4-CP were mainly ascribed to their maximum effective surface area, short mass transfer path and hydrophobic surface, which resulted from their nanoarchitectures with many exposed, shallow and accessible pores and a great deal of nitrogen functionalities.

Synthesis and application of nanoporous triple-shelled CuAl2O4 hollow sphere catalyst for atmospheric chemical fixation of carbon dioxide

Designing complex hollow nano-/microspheres with multilayered structures of two or more metal oxides seems to be interesting to answer the request for novel catalytic structures. Herein, we develop a copper-alumina spinel hollow sphere with a triple-shell structure applied as a novel catalyst for the cycloaddition of CO2 at atmospheric pressure. Different operating conditions such as reaction temperature, various solvents and reaction time were studied in this reaction. Besides, different epoxides were converted at 80 °C, under bubbling of CO2 at atmospheric pressure, a catalyst loading of 3 wt.% and a reaction time of 24 h with isolated yields up to 100% of the carbonate. In addition, the kinetics of the reaction was investigated at different reaction temperatures by calculating the reaction rate constant and activation energy (based on the Arrhenius equation). The nanoporous triple-shell CuAl2O4 hollow microspheres reduce the mass transfer path of different reactant and product molecules along with better accessibility of interior active sites that improves the catalytic efficiency with suitable activity and remarkable cycling stability.

Mn-Promoted Growth of Mg-Based Spinel and Pyroxene Nanostructures.

In this work, we demonstrate Mn-promoted growth of oxide nanostructures standing on a single-crystal MgAl2O4 substrate after heat treatment. Unlike the short truncated spinel pyramids under Au seeds, the addition of Mn produces spinel nanopillars with lengths of 100–300 nm and pyroxene nanowires up to 10 μm. Compared to Au seeds, Au/Mn seeds have different adsorption behavior and therefore provide an additional mass transfer path along seed surfaces that promotes the growth of nanostructures. This vaporization approach has a potential of being applicable to a wide range of complicated oxides.

Electrolytic Nickel Phosphide with One-Dimensional Pore Channels

Nickel phosphide has been widely studied in various applications including electrochemical catalyst, electrode for capacitor, electrode for solar cell and electrode for lithium/sodium ion battery. It is synthesized by a variety of methods including hydrothermal/solvothermal/ionothermal method, ball milling, organometallic method, phosphorization, electroplating, etc. Among them, electroplating has many advantages such as relatively simple equipment set up, easy control of electrodeposit’s composition/thickness/structure by changing plating condition, and simplification of process scale-up. When used as electrochemical functional electrode, porous materials have great kinetic advantages such as decrease in activation overvoltage due to wide surface area and decrease in concentration overvoltage due to open mass transfer path. Well defined porous structure with esp. one-dimensional channels has been usually fabricated using porous template and the process includes at least more than three steps: the application of template, deposition, and removal of template. Apart from the relative complexity of the process, the template might be damaged in the course of experiments and is cost-prohibitive for large scale production. This work reports nickel phosphide thin films with one-dimensional pore channels, prepared by an electrochemical deposition. In particular, it is synthesized by single step process without porous template. Figure shows typical porous structure of the electrolytic nickel phosphide. Based on plating mechanism and observation of deposit’s growth pattern over time, it is suggested that the porous structure is formed by complex factors such as competitive reaction between deposit formation and gas generation, and island-type deposit growth. It was proved that the porous structure can be well controlled by plating conditions such as current density and pH. The electrochemical properties of the porous nickel phosphide thin films were investigated as an electrode for functional electrochemical devices (i.e., batteries and capacitors). The redox processes and interfacial resistance along with energy storage characteristics were analyzed through various electrochemical techniques. In this presentation, the pore formation mechanism of the electrolytic nickel phosphide and the factors governing porous structure will be proposed. In addition, the feasibility of its use as an energy storage materials will be discussed. Figure 1