High Gas Selectivity Research Articles

Trifunctional Monomolecular Medium for Silver Nanoparticle Preparation Preserving Olefin Carrier Activity for Facilitated Olefin Transport Membrane

A trifunctional monomolecular medium, 1-(2-hydroxyethyl)-2-pyrrolidone (HEP), was utilized to show effective reducing and stabilizing activities for the preparation of silver nanoparticles (Ag NPs), along with solvent activity. This HEP also enable to preserve olefin carrier activity of Ag NPs with help of an electron acceptor such as 7,7,8,8-tetracyanoquinodimethane (TCNQ), resulting in high mixed gas selectivity for the separation of propylene/propane mixture in the facilitated olefin transport membrane using Pebax 2533 (poly(amide)-b-ethylene oxide) as polymer matrix.

Solution-processable methyl-substituted semi-alicyclic homo- and co-polyimides and their gas permeation properties

Because of their excellent thermal, chemical and physical properties, as well as high gas selectivity, polyimides are promising polymers for gas separation membranes. However, their commercial use is limited due to their relatively poor solubility and permeability. Here, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-cyclohexane-1,2-dicarboxylic anhydride (DOCDA) was used to improve the solubility of the polyimides, and various methyl-substituted diamines were introduced to increase their permeability, due to the effect of the bulky methyl groups. Polyimides based on DOCDA (DOCDA-PIs), synthesized via one-step solution polymerization, exhibited high solubility in common organic solvents and improved gas permeability due to the non-planar structure of DOCDA and the presence of methyl groups, which disturbed chain packing, an effect that was correlated with increased fractional free volume (FFV) and d-spacing. Co-polyimides based on DOCDA, DOCDA-coPIs, exhibited high gas permeability and CO2/CH4 and O2/N2 selectivity, comparable to commercial polymeric membranes.

Selective Gas Permeation in Graphene Oxide-Polymer Self-Assembled Multilayers.

The performance of polymer-based membranes for gas separation is currently limited by the Robeson limit, stating that it is impossible to have high gas permeability and high gas selectivity at the same time. We describe the production of membranes based on the ability of graphene oxide (GO) and poly(ethyleneimine) (PEI) multilayersto overcome such a limit. The PEI chains act as molecular spacers in between the GO sheets, yielding a highly reproducible, periodic multilayered structure with a constant spacing of 3.7 nm, giving a record combination of gas permeability and selectivity. The membranes feature a remarkable gas selectivity (up to 500 for He/CO2), allowing to overcome the Robeson limit. The permeability of these membranes to different gases depends exponentially on the diameter of the gas molecule, with a sieving mechanism never obtained in pure GO membranes, in which a size cutoff and a complex dependence on the chemical nature of the permeant is typically observed. The tunable permeability, the high selectivity, and the possibility to produce coatings on a wide range of polymers represent a new approach to produce gas separation membranes for large-scale applications.

A strain-controlled C2N monolayer membrane for gas separation in PEMFC application

Ultrathin membranes with controllable pore sizes have great potential to realize high-selectivity gas separation at low energy cost, especially for those mixtures with narrow size distributions. Using a combination of van der Waals-corrected density functional theory (DFT) calculations and molecular dynamics (MD) simulation, we examine the separation ability of biaxial stretched monolayer C2N nanosheets which is applied to the O2 separation from CO/CO2/O2 mixtures in the cathode of proton exchange membrane fuel cells (PEMFC). The DFT calculations show that the diffusion energy barrier for molecules passing through the membrane followed by CO, CO2 and O2 in descending order, and an overall decrease of energy barriers due to the widen the pore size is observed with the increase of applied strains. Furthermore, MD results show that the nanosheet can effectively purify O2 from CO2 and CO with a strain from 8% to 10%. It confirms that the selectivity is determined by the electronic structure related interaction in addition to the kinetic diameter of individual molecules. The O2 permeability is improved progressively with further increase of strain, and small amount of CO2 begins to permeate through the nanosheet at relatively large strain, while the excellent CO isolation is not compromised until the theoretical maximum strain.

Interfacial Engineering of Supported Liquid Membranes by Vapor Cross-Linking for Enhanced Separation of Carbon Dioxide.

Supported liquid membranes (SLMs) based on ionic liquids (ILs) with not only high gas permeability and selectivity, but also high stability under high pressure, are highly desired for gas separation applications. In this work, permeable and selective polyamide network (PN) layers are deposited on the surface of SLMs by utilizing the cross-linking reaction of trimesoyl chloride, which was pre-dispersed in the SLMs, and vapor of amine linkers. The vapor cross-linking method makes it easy to control the growth and aggregation of PN layers, owing to the significantly reduced reaction rate, and thereby ensuring the good distribution of PN layers on the surface of SLMs. With rational choice of amine linkers and optimization of vapor cross-linking conditions, the prepared sandwich-like PN@SLMs with ILs embedded homogeneously within polymeric matrices displayed much-improved CO2 permeability and CO2 /N2 selectivity in relation to the pristine SLMs. Moreover, those SLMs with ILs impregnated into porous supports physically displayed improved stability under high pressure after vapor cross-linking, because the PN layers formed on the surface of SLMs help prevent the ILs from being squeezed out. This interfacial engineering strategy represents a significant advance in the surface modification of SLMs to endow them with promising applications in CO2 capture.

High Selective Gas Detection for small molecules based on Germanium selenide monolayer

Abstract Predictive calculations based on density functional theory (DFT) are used here to study the electronic and optical properties of GeSe monolayer after adsorbing gas molecules (O2, NH3, SO2, H2, CO2, H2S, NO2, CH4, H2O, NO, CO). Our results reveal that for all the gas molecules considered, only NH3 is adsorbed on GeSe monolayer by physisorption. Whereas SO2 and NO2 are chemisorbed on GeSe monolayer with strong adsorption energies. In addition, the adsorption of O2, NO and NO2 distinctly enhances the optical absorbance and broaden the absorbance range of GeSe monolayer in visible light region. Also, it is found that the adsorption of H2S, NO and NH3 can reduce the work function of the GeSe monolayer. The results indicate that GeSe monolayer is not only a promising candidate for the sensing, capture, and storage of NH3, but also an anticipated disposable gas sensor or metal-free catalyst for detecting and catalyzing SO2 and NO2. Furthermore, it has excellent potential to be applied to optical sensors, solar cells, nanoelectronics or optoelectronics devices.

A high selective methanol gas sensor based on molecular imprinted Ag-LaFeO3 fibers

Ag-LaFeO3 molecularly imprinted polymers (ALMIPs) were fabricated, which provided special recognition sites to methanol. Then ALMIPs fiber 1, fiber 2 and fiber 3 were prepared using filter paper, silk and carbon fibers template, respectively. Based on the observation of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Nitrogen adsorption surface area analyzer (BET), the structure, morphology and surface area of the fibers were characterized. The ALMIPs fibers (fiber 1, fiber 2 and fiber 3) show excellent selectivity and good response to methanol. The responses to 5 ppm methanol and the optimal operating temperature of ALMIPs fibers are 23.5 and 175 °C (fiber 1), 19.67 and 125 °C (fiber 2), 17.59 and 125 °C (fiber 3), and a lower response (≤10, 3, 2) to other test gases including formaldehyde, acetone, ethanol, ammonia, gasoline and benzene was measured, respectively.

Synthesis and Characterization of Functional Triphenylphosphine‐Containing Microporous Organic Polymers for Gas Storage and Separation

AbstractTwo kinds of novel triphenylphosphine‐containing microporous organic polymers are designed and synthesized via palladium‐catalyzed Sonogashira−Hagihara coupling condensation reaction of triphenylphosphine oxide‐ and sulfide‐based monomers with different arylethynylene linkers. The gas adsorption isotherms reveal that these polymers have strong binding affinity for CO2 with high CO2 adsorption capacity, although they have moderate Brunauer−Emmett−Teller surface area ranging from 684 to 883 m2 g−1. Among the resulting polymers, triphenylphosphine oxide–tris(4‐ethynylphenyl)amine exhibits the highest CO2 uptake capacity of 2.61 mmol g−1 at 273 K and 1.13 bar with relatively high gas selectivity of 60.2 for CO2 over N2 at 273 K.

Efficient separation of helium from methane using MOF membranes

Traditional separation methods of helium recovery are energy intensive and economically disadvantageous. Considering the potential deficit of helium, it is very important to develop efficient technologies for helium recovery from natural gas sources. Metal organic frameworks (MOFs) have emerged as strong alternatives to traditional membrane materials due to their wide range of pore sizes, permanent porosities, and high surface areas. Only a small number of MOF membranes has been fabricated and experimentally tested for He/CH4 separations. In this study, we performed the first large-scale computational study to predict He/CH4 separation performances of various MOF membranes. First, we compared predictions of our molecular simulations with the experimentally available data for He permeability of several MOF membranes. Motivated from the good agreement between experiments and simulations, we examined 139 different MOF membranes for He/CH4 separation. Selectivity and permeability of the MOF membranes were compared with those of traditional polymer and zeolite membranes. A significant number of MOF membranes was identified to exceed the Robeson’s upper bound due to their high gas selectivities and permeabilities. We also compared ideal and mixture selectivities of MOF membranes performing molecular simulations both for single-component gases, He and CH4, and binary gas mixtures of He/CH4. Results showed that selectivities and permeabilities of MOF membranes calculated using the single-component gas data can significantly overestimate the ones calculated using the mixture data. Results of this study will be useful to guide the experiments for selecting the most promising MOF membranes for efficient He/CH4 separations.

An array of metal oxides nanoscale hetero p-n junctions toward designable and highly-selective gas sensors

Nano-helical array of p-NiO/n-SnO2p-n junctions with well-defined and highly-gas-accessible hetero-interfaces is presented for designable and highly selective gas sensors. The gas sensor having the nanoscale p-n junction sensing layer with a top-and-bottom electrodes configuration was fabricated by conventional photolithography and oblique-angle deposition. The unique device structure enables a predominant modulation in barrier height at the hetero-interfaces, consistent with simulation results, resulting in unusual-yet-promising sensing behaviors upon H2 and NO2 exposure. Based on our experimental and simulation results, and the ability to fabricate a variety combination of metal oxides heterostructures with a reproducible and controllable way, we believe that it becomes possible to design and realize highly-selective sensor array electronic-noses optimized towards target gases on demand.

Ultra-high sensitive and selective H2 gas sensor manifested by interface of n–n heterostructure of CeO2-SnO2 nanoparticles

Detection of toxic and explosive gases in a selective manner and with higher sensitivity in industries and homes remains very challenging. Therefore, herein, we report on the ultra-high sensitive and selective hydrogen gas sensing using CeO2-SnO2 mixed oxide heterostructure synthesized by a simple hydrothermal method. The BET, photoluminescence, X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses demonstrated that the CeO2-SnO2 heterostructure comprehends a high surface area and a large number of defects related to oxygen vacancies. The formation of heterojunction in CeO2-SnO2 nanostructures was confirmed by the non-linear behaviour I–V curve. The gas-sensing characteristics of the CeO2-SnO2 heterostructure showed shorter response and recovery times of approximately 17 and 24s, respectively, together with high sensitivity (19.23ppm−1) to 40.00ppm H2 gas at 300°C. The improved H2 gas sensing response of 1323 at 60ppm H2 gas is correlated with the higher surface area, pore diameter, surface defects and CeO2-SnO2 heterojunction emerging at the interfaces between the CeO2 and SnO2 serves as additional reaction sites and as well as exposed facets creating the surface to be extremely reactive for the adsorption of oxygen species. The high H2 gas selectivity observed for the CeO2-SnO2 makes them possible candidates for monitoring H2 gas at low concentrations (ppm levels).

High Gas Uptake and Selectivity in Hyper‐Crosslinked Porous Polymers Knitted by Various Nitrogen‐Containing Linkers

By introducing various N‐containing compounds as efficient linkers, a series of hyper‐crosslinked porous polymers with high surface areas and gas‐uptake values were synthesized by using the Friedel–Crafts alkylation reaction. Structural characterization indicated the presence of nitrogen atoms, and gas‐sorption experiments revealed that the high gas uptake benefitted from the high surface areas and the incorporation of N‐containing linkers as Lewis basic sites. Among these porous polymers, HCP‐4 had the highest H2 uptake of 9.29 mmol g−1 at 77 K and 0.1 MPa and the highest C2H2 uptake of 6.69 mmol g−1 at 273 K and 0.1 MPa, whereas HCP‐3 showed the best CO2 uptake of 4.42 mmol g−1 at 273 K and 0.1 MPa. To understand better the important role played by nitrogen in these polymers, the isosteric heat of adsorption and adsorption selectivity of CO2 over N2 were calculated. The results showed that the triazine‐based polymer HCP‐1 had the highest CO2 over N2 selectivity of 75.4 at 295 K and 0.1 MPa, which makes it the most potential candidate for CO2 capture.

Amorphous In-Ga-Zn-O Powder with High Gas Selectivity towards Wide Range Concentration of C₂H₅OH.

Amorphous indium gallium zinc oxide (a-IGZO) powder was prepared by typical solution-based process and post-annealing process. The sample was used as sensor for detecting C2H5OH, H2, and CO. Gas-sensing performance was found to be highly sensitive to C2H5OH gas in a wide range of concentration (0.5–1250 ppm) with the response of 2.0 towards 0.5 ppm and 89.2 towards 1250 ppm. Obvious difference of response towards C2H5OH, H2, and CO was found that the response e.g., was 33.20, 6.64, and 2.84 respectively at the concentration of 200 ppm. The response time and recovery time of was 32 s and 14 s respectively towards 200 ppm concentration of C2H5OH gas under heating voltage of 6.5 V.

Homopolymer and multi-block Diels-Alder polyphenylenes: Synthesis, physical properties, X-ray diffraction, and gas transport

A gas transport and X-ray structural analysis is reported for a methylated poly(phenylene) (MPP) and non-methylated poly(phenylene) (PP) homopolymer, a random copolymer, and MPP-PP block copolymers synthesized using Diels-Alder chemistry. These highly rigid and aromatic polymers display Tg’s of 400°C and 382°C for PP and MPP. Multi-block copolymerization of PP and MPP had a significant effect on the spatial arrangement of polymer chains as revealed by changes in the X-ray diffraction amorphous peak. The membranes displayed a narrower fractional free volume (FFV) from 0.288 to 0.304. The gas permeability, solubility, diffusivity and selectivity data for He, H2, O2, CO2, N2, and CH4 were determined for this polymer series. Gas permeability variation between PP and MPP was 1.5% for H2 (134 Barrers) and 16% for N2 (7.11 Barrers). However, the multi-block MPP-PP-B2 led to permeability increases between 22.4% for H2 (164 Barrers) and 61.7% for N2 (11.5 Barrers). This work reveals clear relationships between the ordering of the amorphous region and gas diffusivity and solubility. The permselectivity trade-off did not correlate well to gas kinetic diameter (KD), polymer chemistry or composition, and depended largely on the gas pair. This poly(phenylene) family displayed high permeability and moderate ideal gas selectivity that were near the upper bound. Permselectivity results are compared to polyphenylene oxide (PO), functionalized PO using (NH2 and NO2), 6FDA-DABA, and 6FDA-mPDA.

Effective enhancement of gas separation performance in mixed matrix membranes using core/shell structured multi-walled carbon nanotube/graphene oxide nanoribbons

Novel core/shell structured multi-walled carbon nanotube/graphene oxide nanoribbons (MWCNT@GONRs) nanohybrids were successfully prepared using a modified chemical longitudinal unzipping method. Subsequently, the MWCNT@GONRs nanohybrids were used as fillers to enhance the gas separation performance of polyimide based mixed matrix membranes (MMMs). It is found that MMMs concurrently exhibited higher gas selectivity and higher gas permeability compared to pristine polyimide. The high gas selectivity could be attributed to the GONRs shell, which provided a selective barrier and large gas adsorbed area, while the high gas permeability resulted from the hollow structured MWCNTs core with smooth internal surface, which acted as a rapid transport channel. MWCNT@GONRs could be promising candidates to improve gas separation performance of MMMs due to the unique microstructures, ease of synthesis and low filling loading.

Development of a Catalytic Combustion Type Gas Sensor with Low Power Consumption

Currently, gas leak alarms using AC power-supply are popular in Japan. However, there is pointed out, such as the hassle of installation property and power cord of the alarm, there was an increasing demand of the alarm of a battery drive system. The gas sensor of very low power consumption was required for realizing the battery operating system. Therefore, we focused on MEMS technology. The heating element occupying power most of for operating the sensor has been developed micro heater using a MEMS technology. The micro-heater has a rapid thermal response of several tens of milliseconds after the supply power. Furthermore, we developed a catalytic combustion type gas sensor reduced to 1/1000 of conventional power consumption by using the detection method of the intermittent operating. In general, miniaturization of the gas sensor would have a negative effect. Those effects were decreasing of the sensitivity / noise ratio and tending to susceptible to environmental factors. In this study, we report on improvement of the sensor for high sensitivity and high gas selectivity. The micro-heater was formed by sputtered platinum pattern on a silicon wafer. Formed platinum membrane was covered with a silicon nitride film. It is an air-bridge structure of the square of 90μm angle, suspended by etching the heater backside. The micro-heater has low power consumption because its thermal capacity is low. The catalytic combustion type micro-gas-sensor was prepared by sintering materials that Pd loaded γ-Al2O3 for a sensing element and only γ-Al2O3 for a reference element. The catalytic combustion type micro-sensor to give amplifies the potential difference generated both elements by a resistance change of the heater according to the catalytic combustion reaction of combustible gases. Measurements of gas sensitivity of the sensor which was heated to approximately 450°C， placed in a gas chamber, it was performed by injecting a test gas having a predetermined concentration. Response carve of the sensor when power was supplied to the micro-heater becomes detectable state at tens of milliseconds. Methane sensitivity was observed with good linearity. However, the hydrogen sensitivity was approximately three times the methane it, methane selectivity of the sensor was found to be low. Material of the reference element in order to improve this problem has been changed. The reference element materials have used γ-Al2O3 does not have catalytic combustion reaction with any combustible gases. The reference element material was to have sensitivity to miscellaneous gases such as hydrogen by changing from γ-Al2O3 in the Pt loaded γ-Al2O3. Miscellaneous gas sensitivity of each element cancelled each other, the selectivity of methane sensitivity was improved. As a result, the sensitivities of H2 / CH4 ratio have become possible to improve the methane selectivity to 1 times or less. The second improvement was to increase the methane gas sensitivity. By the small size of the device due to the low power consumption, the amount of catalyst could be applied would be very small. Further, since the planar structure, the detection target gas could react only one side of the catalyst, the sensitivity obtained by the combustion reaction was low. Therefore, we consider how to increase the gas contact point on the element. As a first method, it was optimize the amount of Pd supported on the catalyst. If the amount of Pd loaded ratio is substituted standard ratio for 1, the sensitivity of the methane was found to be a maximum value in the Pd ratio is 2. On the other hand, the specific surface area was decreased with an increase in the amount of Pd loaded in particular reduction of the specific surface area more than Pd ratio is 2 was significant. When the amount of Pd loaded increases gas contact points, gas sensitivity is improved to increase. However, the sensitivity is found to decrease by a metal agglomeration when Pd loaded content is too high may occur. As a second method, utilizing the characteristics of the sensor elements consists of an air-bridge, in order to encourage gas contact from the heater backside, some slit-shaped through-hole between the heater patterns. It becomes possible to wrap the catalyst heater backside by the structural modification. Then methane gas sensitivity of the sensor by gas contact point of the heater back side increases has been improved by 40% compared with the previous type. These improvements had the prospect of practical use of methane gas sensor of the catalytic combustion type with micro-heater using MEMS technology.

CO2 separation through poly(vinylidene fluoride-co-hexafluoropropylene) membrane by selective ion channel formed by tetrafluoroboric acid

In this study, we showed for the first time that polymer electrolyte membranes consisting of tetrafluoroboric acid solution (HBF4) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) could be utilized for CO2 separation. We utilized tetrafluoroboric acid solution to increase the solubility of CO2 in PVDF-HFP membranes. Strong acidic HBF4 could be easily solvated by water molecules and then well distributed in PVDF-HFP chain. The hydrated protons generated by HBF4 in polymer chains could be selective channels for CO2 transport, resulting in high separation performance. The interaction between fluorine in PVDF-HFP and proton ions in HBF4 was investigated by FT-IR and Raman spectroscopy. Thermal gravimetric analysis (TGA) data demonstrated thermal stability of the membrane after the addition of HBF4 and formation of hydrated proton ions. The hydrated proton ions significantly increased the solubility of CO2 gas, resulting in both high selectivity and high gas permeance for CO2 (CO2/N2=25 and 25 gas permeance unit (GPU), respectively).

Influence of Ethanol on Breath Acetone Measurements Using an External Cavity Quantum Cascade Laser

Broadly tunable external cavity quantum cascade lasers (EC-QCLs) in combination with off-axis integrated cavity enhanced spectroscopy (OA-ICOS) provide high molecular gas sensitivity and selectivity. We used an EC-QCL in the region of 1150–1300 cm−1 in both broadband scan mode, as well as narrow scanning mode around 1216 cm−1, respectively, for detection of acetone in exhaled breath. This wavelength region is essential for accurate determination of breath acetone due to the relative low spectral influence of other endogenous molecules like water, carbon dioxide or methane. We demonstrated that ethanol has a strong spectroscopic influence on the acetone concentration in exhaled breath, an important detail that has been overlooked so far. An ethanol correction is proposed and validated with the reference measurements from a proton-transfer reaction mass spectrometer (PTR-MS) for the same breath samples from ten persons. With the ethanol correction, both broadband and narrowband molecular spectroscopy represent an attractive way to accurately assess the exhaled breath acetone. The importance of considering spectroscopic ethanol influence is essential, especially for the narrowband scans, (e.g., 1216 cm−1), for which the error in determining the acetone concentrations can rise up to 39% if it is not considered.

New Syngas Reforming Solutions for Enhanced Gas-to-Diesel Conversion

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 177660, “New Syngas Reforming Solutions for Enhanced Gas-to-Diesel Conversion,” by Conrad Ayasse and Rob Ayasse, Verdis Synthetic Fuels, prepared for the 2015 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 9-12 November. The paper has not been peer reviewed. This paper presents an overview of the challenges of using traditional synthesis gas reforming methods for efficient gas-to-liquids (GTL) conversion. A second objective is to show how newly emerging reformer technologies, such as those based on plasma or catalytic partial oxidation, will provide significant improvements. A case also will be made for how these new technologies, when paired with a high-efficiency Fischer-Tropsch (FT) process, provide a profitable alternative to the environmentally damaging, and wasteful, practice of flaring or venting associated gas. Introduction Given the limitations of footprint, weight, safety, cost, and other factors for platform operations, the use of the FT process for flared-gas conversion to liquids is challenging. This study shows that the best process uses a catalytic partial-oxidation reformer, a unique wax-free FT catalyst, and an advanced FT reactor to meet all platform criteria while cutting traditional capital expenditures (Capex) and operational expenditures (Opex) in half. Criteria for Platform Operations The following criteria were considered for the selection of equipment on a platform: Small footprint (space limitations) Low weight (weight limitations) Low pressure (safety considerations) High gas hourly space velocity (GHSV) (to enable small reactors) Low pressure drop at high GHSV (reactor shape) High gas conversion (process efficiency) High gas selectivity to carbon monoxide (process efficiency) No water needed (simplicity) No pure oxygen needed (platform requirement for safety) No feed-gas preheat needed (simplicity) No reformer tail-gas heat exchanger needed (simplicity) At the heart of the list are footprint, weight, and safety. From the safety perspective, temperature, pressure, and oxygen concentration are important. Equipment footprint and weight affect the platform cost and the ability to add equipment to existing platforms. This means that the number of process-unit operations must be kept at a minimum.

Separation of gas mixtures by new type of membranes – Dynamic liquid membranes

Abstract The selectivity and permeability of membrane material determines the efficiency of the gas separation process. To prepare a stable high selective and high permeable membrane and, in addition, also cheap, is the dream of most scientists dealing with the membrane technology. We proposed to investigate the gas separation by a completely new type of membranes possessing both; high selectivity and high gas permeability. Our preliminary results are very promising. We are able to prepare a very cheap and very thin liquid film with high separation performance of test CO2/CH4 mixture. A next curiosity of the new type of membranes is the continuous regeneration of the liquid film during the separation process. Based on this fact, we named the liquid film “dynamic liquid membrane” (DLM).