37 results about "Macromolecule degradation" patented technology

The invention relates to bio-enzyme gel breaker, in particular to formula and technique for gel breaking of water-based guargum fracturing fluid by using the bio-enzyme gel breaker. The bio-enzyme gel breaker contains the following components in percentage by weight: 10-50% of beta- mannose, 0-20% of cellulose, 0-10% of pectinase, 0-15% of glucanase, 0-10% of xanthase, 3-10% of (NH4)2SO4, 2-5% of NaCl, 1.5-5% of ZnCL2 and 0-60% of persulfate. The fracturing fluid gel breaking technique comprises the following steps: dissolving the bio-enzyme gel breaker in borax crosslinked fluid; mixing and blending the crosslinked fluid and the guargum base fluid, crosslinking, forming jelly, and then mixing with proppant, pressing the mixture into the oil-water well until the mixture enters the fractured crack. In this way, the fracturing process is finished. The bio-enzyme gel breaker degrades the macromolecular guargum in the stratum fracturing fluid into small micromolecular sugar, and when the jelly breaks up, the proppant is left underground, the fracturing gel breaking fluid flows back, and in this way, the construction can be completed. The bio-enzyme gel breaker has good gel breaking performance, the construction process is reasonable, the viscosity of the fracturing fluid can not decrease too early, the gel of the fracturing fluid can be broken evenly and thoroughly with little residue and small harm to the stratum, and the operation is simple and convenient.

The invention discloses a production method of an excellent solvent of ultrahigh molecular weight polyethylene and a fiber thereof. The production method is characterized in that the ultrahigh molecular weight polyethylene can be dissolved in the solvent at a temperature being lower than a decomposition temperature of the ultrahigh molecular weight polyethylene to form a homogeneous solution, thereby reducing a macromolecule degradation degree in a dissolving and untwisting process of the ultrahigh molecular weight polyethylene and meanwhile increasing homogeneity of a formed jelly solution to ensure homogeneity and spinnability of primary precursor fibers during a production process of an ultrahigh molecular weight polyethylene fiber. Compared with other spinning solvents and spinning methods, the production method and the solvent in the invention can enable a solvent mass content in the primary precursor fibers to be not more than 2%, breaking strength of the ultrahigh molecular weight polyethylene fiber to be increased by 7-11% and a breaking modulus to be increased by 17-42%.

The invention belongs to the technical field of macromolecule degradation and catalysis, and relates to a preparation method of a low-eutectic solvent catalyst and application thereof to the PET alcoholysis process. Urea compounds 1,3-dimethylurea, trimethyl-urea and 1,1 dimethylurea are used as hydrogen bond donors of a low-eutectic solvent to perform complexation reaction with inorganic zinc salts and inorganic manganese salts; a metal compounding low-eutectic solvent is formed; the low-eutectic solvent can be used as catalysts to be applied to PET alcoholysis reaction; the advantages of high catalysis activity and high reaction speed are realized; the potential application prospects are realized.

The invention relates to a method for preparing organic chemicals through photocatalytic oxidation degradation of biomass, and belongs to the method for preparing the organic chemicals through the biomass. According to the photocatalytic oxidation method, a modified photochemical catalyst is used for being coupled with an oxidant, a photocatalytic oxidation system is established, so that the biomass is high-efficiently degraded under a mild condition, and a feasible way is further provided for extraction and utilization of high added value chemicals in the degraded products. The method comprises the following steps of firstly, synthesizing a metal-nonmetal load type TiO2 photochemical catalyst, then using a liquid phase chemical reagent as the oxidant, adjusting the pH value to be alkalic, performing irradiation with sunlight or ultraviolet light, and establishing the photocatalytic oxidation system. The system can effectively degrade organic macromolecules of the biomass into small molecules, and high added value chemicals comprise aldehyde, alkone, carboxylic acid and other aromatic compounds. The method disclosed by the invention has the advantages of cleanness, high efficiency, good selectivity, low cost and the like, can develop a new way for mild and rapid degradation of the biomass, and realize cleanness, the high efficiency and the comprehensive utilization of the biomass.

The invention relates to the technical field of water culture fertilizer, and specially relates to a preparation method of a water culture fertilizer for hydroponic crops. According to the preparation method, in a coating machine, an alginate water solution is used to carry out a coating treatment, then a crosslinking agent water solution is adopted to carry out a wrapping treatment to prepare dry particles; then an epiboly agent is added to carry out an epiboly treatment; after the alginate water solution reacts with the crosslinking agent water solution and the epiboly agent; the sustained-release period is prolonged, the water culture environment is improved; furthermore, as the sustained-release period is prolonged continuously, the alginate macromolecules are degraded into micromolecules, the fertilizer in the wrapped layer is completely released; after the sodium citrate in fertilizer particles is released, the alginate gel can be dissolved quickly, the alginate gel is decomposed, and the quality of water culture nutrient solution is improved.

The invention discloses a biological waste fungicide and a preparation method thereof. The biological waste fungicide comprises a fungicide component and an extract component, wherein the fungicide component contains the following raw materials in percentages by weight: 15-40% of lactic acid bacteria, 1-10% of actinomycetes, 2-10% of bacillus, 8-15% of photosynthetic bacteria and 9-14% of enterococcus faecalis; the extract component contains the following raw materials in percentages by weight: 25-35% of a natural plant extract, 15-26% of lactic acid, 8-15% of citric acid and 6-18% of sodium benzoate. By using the synergistic effect of compound microorganisms, harmful substances and an odor source in biological wastes are effectively decomposed and absorbed to achieve the targets of sterilization and deodorization; and a few of macromolecules are degraded into micromolecules through anaerobic fermentation reaction of the microorganisms such as the lactic acid bacteria, thereby completing the biological degradation process.

The invention discloses a wastewater biochemical treatment method, and specifically discloses a method for treating PVC (Polyvinyl Chloride) mother liquor by utilizing MBR (Membrane Bioreactor) technique. The method comprises the following sequential process schemes: carrying out anaerobic reaction treatment on the PVC mother liquor with PVA (Polyvinyl Alcohol)-containing degrading bacteria, wherein the anaerobic reaction temperature is controlled at 20-35 DEG C, the reaction time is controlled at 6-10h, and the dissolved oxygen is controlled at 0.1-0.2mg / L; degrading organic macromolecules into micromolecules so as to improve biodegradability; and then introducing anaerobic reaction effluent to the MBR for aerobic treatment so as to ultimately obtain clean water with COD (Chemical OxygenDemand) not more than 30mg / L, wherein bacilli is contained in the MBR. The method has the advantages that treatment cost is only needed to be invested at one time, and long-term and stable treatment can be realized by expending low maintenance cost and electric cost in the following years; the longer the use time is, the lower the average treatment cost of per ton of wastewater is; and the methodcan be widely applied to sewage treatment enterprises.

The invention discloses environment engineering sewage purification treatment equipment. Sewage is collected and gathered into a main tube, and is firstly fed into a grating septic tank, and sewage after grating baffle treatment flows into a water quantity and quality adjusting tank for water quantity adjustment and water quality homogenization; three-dimensional elastic packing is mounted in a hydrolytic acidification reaction tank, and then the number of microorganisms in a unit volume can be increased; under the action of a great amount of hydrolysis bacteria and acidification bacterial, macromolecule degradation-refectory pollutants can be hydrolyzed into micro molecule easily degraded substances, furthermore the biodegradability of sewage is improved, and a base is made for later treatment processes; an effluent flows into an A / O biochemical pool and is reduced into C, N and O at molecular states; the effluent flows into an internal MRB (membrane bioreactor), and filtrate is gathered into a sterilization tank through an MRB membrane component water collection tube; residual sludge is discharged into the septic tank and is sucked and transported out by a fecal suction truck atregular time; a waste gas treatment device is adopted to deodorize and discharge waste gases into upper air, a high sewage treatment efficiency is achieved, up-to-standard emission of waste gases andstrong harmless sewage treatment capabilities can be achieved.

The invention discloses a naphthalene detecting biological cell sensor, as well as a preparing method and a use method thereof. A gene recombination cell is used as the naphthalene detecting biological cell sensor, a salicylic acid detecting light sensing cell is used as a host cell of the gene recombination cell, and a plasmid of the gene recombination cell is recombined by a naphthalene degrading gene and a vector plasmid. The naphthalene detecting biological cell sensor can immediately emit light at the presence of naphthalene and has the advantages of great selectivity, high flexibility, high analysis speed, simplicity in operation, low instrument price and capability of carrying out continuous and stable online detection in a complicated system. The invention further provides a preparing method for the cell sensor. Adopted construction conditions are mild, the method is controllable, simple and feasible, the in-vitro recombination of a macro-molecular degrading fragment is finished by a Gibson cloning technology, and an important means is provided for the detection of a specific pollution substrate.

The invention relates to a biodegradable poly-terephthalic acid type foaming material and a preparation method thereof. The foaming material is prepared by the following method that (1) poly-terephthalic acid type plastics and a degradation agent are put into a first multiple screw extruder; shear melting is performed to form a first hot melt with mobility; (2) the first hot melt is pumped into ascrew reactor; then, a chain extender is added for reaction; (3) the reacted melt body is then pumped into a second multiple screw extruder; then, a cross-linking agent, a nucleating agent and a foaming agent are added; mixing and homogenizing are performed; (4) a homogeneous melt body obtained in the step (3) is output and is foamed and formed. Compared with the prior art, the foaming material and the preparation method have the advantages that DNA sequence recombination is simulated for performing the processes of macromolecule degradation crushing, molecule fragment unordered reconstitutionand the like; a superhigh polymer structure with a multifunctional side chain and a functional fragment at a main chain is generated; the foaming operation time, the temperature window and the like are optimized; the physical property enhancement and the continuous controllable and stable forming of the poly-terephthalic acid type foaming material are realized.

The invention provides a hydrodynamic cavitation device for treatment of domestic sewage. The hydrodynamic cavitation device comprises a rotary shaft and a stator. A cavitation cavity is formed in thestator, a blind hole is formed in the inner wall of the cavitation cavity, and a water inflow pipe and a water outflow pipe are arranged on the stator. The rotary shaft is mounted in the stator, oneend of the rotary shaft stretches out of the stator, the stretching end is connected with a transmission device, a rotor is arranged on the rotary shaft, the rotor is located in the cavitation cavityof the stator, and a blind hole is distributed in the rotor. The domestic sewage is input in the stator cavitation cavity of the device through a water pump, sufficient cavitation bubbles are generated in the device through mechanical rotation, the cavitation bubbles instantly collapse to form microjet and shock waves, instant local high temperature and instant high pressure are generated, cavitation is more violent, the cavitation efficiency is improved, macromolecules difficult to treat in the sewage are degraded into micromolecules easily decomposed relatively, and the cavitation jet generated by the hydrodynamic cavitation device has a purification effect on the domestic sewage. The hydrodynamic cavitation device is high in treatment efficiency and good in effect, and the following treatment efficiency can be improved.

The invention provides a production method of compound bacterium solid-state fermented maize protein meal and belongs to the technical field of biological feed. The production method comprises the following steps: 1, selecting maize protein meal which is sieved with a 40-mesh sieve as a fermentation raw material; 2, preparing compound bacterium fermented seed liquid with the viable count of 1.0*10<8>cfu / ml to 1.0*10<9>cfu / ml; 3, inoculating the compound bacterium fermented seed liquid into the maize protein meal according to the amount of 6 percent, wherein the moisture content is 50 percent and the pH value is natural; uniformly mixing to obtain a fermentation basic material; 4, spreading the fermentation basic material to the bottom of a fermentation tank according to the thickness of 40cm to 50cm and keeping the temprature of the fermentation tank at 30 DEG C to 35 DEG C; carrying out anaerobic fermentation for 72h to 96h to obtain fermented maize protein meal; 5, drying the fermented maize protein meal at the temperature of 50 DEG C to 55 DEG C and cooling to a room temperature to obtain a compound bacterium solid-state fermented maize protein meal finished product. Maize protein macromolecules can be degraded into small peptides, free amino acids and the like and a bitter taste is effectively removed so that the palatability is improved; the compound bacterium solid-state fermented maize protein meal can be used as a high-quality protein feed resource and can be used for remarkably improving immunity functions of animals when being added into feed.

The invention provides an anaerobic dynamic membrane reactor for efficiently treating degradation-resistant wastewater, and aims to effectively remove organic matters and suspended solids (SSs) in high-concentration wastewater. An indent dynamic membrane component is used, the thickness of a dynamic membrane is quantitatively controlled through shearing force generated by a circulation gas and a baffle plate of a certain thickness, backwash cleaning is avoided, a dynamic membrane layer is prevented from dissociation, and thus effluent quality stability can be ensured. Conductive carbon cloth is adopted as a carrier material for forming a bio-membrane, microorganisms with electron transfer can be enriched, the electron transfer efficiency of microorganisms of the dynamic membrane layer canbe improved, and furthermore the organic matter degradation and the anaerobic methanogenesis efficiency can be improved. Meanwhile, SSs and macromolecule degradation-resistant organic matters (greaterthan 4000Da) in wastewater can be effectively retained by the dynamic membrane layer, the effluent quality can be improved, and later treatment on effluents can be facilitated. In addition, the anaerobic dynamic membrane reactor is simple in operation and low in cost.

The invention discloses fruit, vegetable and cyclodextrin supermolecule micro-powder, a method for preparing the same and application of the fruit, vegetable and cyclodextrin supermolecule micro-powder.The fruit, vegetable and cyclodextrin supermolecule micro-powder is mainly made of cyclodextrin, fruits and vegetables.Compared with the prior art, the fruit, vegetable and cyclodextrin supermolecule micro-powder, the method and the application have the advantages that technical difficult problems in the aspect of micronizing fruits and vegetables can be solved by the aid of the simple technological method, the original contents of components of the fresh fruits and the fresh vegetables can be kept to the greatest extent, degradation of macromolecules can be promoted, the contents of water-soluble small-molecular components can be increased, and products have high nutritional available value; the dispersibility and the solubility of the fruits and the vegetables can be improved, nutrition absorption and utilization can be enhanced, and the fruit, vegetable and cyclodextrin supermolecule micro-powder has excellent taste and is low in dose and high in compliance; optional chemical reagents or solvents are omitted in preparation procedures, and accordingly the fruit, vegetable and cyclodextrin supermolecule micro-powder is high in safety; the products are good in flowability, follow-up preparation processing can be facilitated, and the fruit, vegetable and cyclodextrin supermolecule micro-powder is excellent in performance and has fine and uniform particle sizes; the powdery products and preparations are good in stability, long in shelf life and easy to carry, store and transport; the technical method is simple and is free of emission or pollution, and accordingly the fruit, vegetable and the cyclodextrin supermolecule micro-powder, the method and the application conform to the 'efficient, high-quality and environment-friendly' development direction of the food processing industry.

The invention relates to a mixed tobacco fermentation method. The method comprises the following steps of respectively inoculating bacillus subtilis and phaffia rhodozyma on an LB agar culture medium and a YPD agar culture medium, respectively culturing for 24 hours at 37 DEG C and culturing for 5-7 days at 22 DEG C to obtain single colonies of the bacillus subtilis and the phaffia rhodozyma; respectively inoculating the single colonies into an LB liquid culture medium and a YPD liquid culture medium, respectively culturing for 20 hours at 37 DEG C and culturing for 28-29 hours at 22 DEG C to obtain a bacillus subtilis seed solution and a phaffia rhodozyma seed solution, and mixing the bacillus subtilis seed solution and the phaffia rhodozyma seed solution in an isopyknic manner to obtain a mixed bacterium solution; centrifuging the mixed bacterial liquid, collecting thalli and washing; resuspending the washed thalli to obtain a bacterial suspension; and adding the bacterial suspension and rhizopus powder into tobacco leaves, and fermenting at 25 DEG C for 7-10 days. By means of the method, the bacillus subtilis, the phaffia rhodozyma and the rhizopus are compounded and mixed, so that macromolecules such as starch and protein which have negative effects on the quality of the tobacco leaves can be degraded into alcohols, lipids, aldehydes and aroma small molecular substances, and the quality of the tobacco leaves is effectively improved.

The invention relates to a biomacromolecule cracking device and a detection system thereof. The biomacromolecule cracking device comprises: an ionization chamber which includesan inner chamber, a sample inlet and a sample outlet, wherein the inner chamber is used for accommodating a sample, and the sample inlet and the sample outlet are communicated with the inner chamber; a low-temperature discharge unit which comprises an upper electrode and a lower electrode, the ionization chamber is arranged between the upper electrode and the lower electrode, and the upper electrode and the lower electrode are opposite to the inner chamber; a heating electrode which is used for heating the sample in the inner chamber; and an ultrasonic electrode wich is used for carrying out ultrasonic treatment on the sample in the inner chamber. The biomacromolecule cracking device provided by the invention can degrade water-soluble biomacromolecules into micromolecule fragment products with uniform products and controllable sizes.

The invention relates to a live food for river crab seedling breeding and a preparation method thereof. The food is complete in nutrients, has basically balanced amino acid components in protein and can adapt to a breeding environment and biological habits of river crabs. According to the food, the content of the protein is relatively high, the content of crude protein can reach 38-40%, the micro-powder food has stable suspension property in water and can be directly absorbed and digested by river crab seedlings. The live food for the river crab seedlings is rich in multiple active probiotic strains, is very strong in vitality and strong in metabolism after being put into a water body, and can rapidly proliferate and generate a large number of extracellular enzymes; macromolecules, such asresidual food and fish and shrimp wastes in the water are degraded into micromolecules, such as organic acids and amino acids; and abundant nutrients are provided for reproduction of diatoms and plankton. Meanwhile, probiotics play roles in ammoniation, nitrification, vulcanization and nitrogen fixation, remove toxic substances, such as the amino acids, nitrites and hydrogen sulfide in the waterbody, reduce chemical oxygen demand and biological oxygen demand, indirectly increase the amount of dissolved oxygen and purify the water.

The invention discloses a ligustrum lucidum ait hide glue health drink and its preparation method. The ligustrum lucidum ait hide glue health drink comprises a hide glue enzymatic hydrolysate, a ligustrum lucidum ait extracting solution, an antioxidant and a sweetener. Protease is used for initial enzymolysis of hide glue, and the hide glue is then degraded from macromolecules to peptone or oligo-peptide which is beneficial to absorption. Thus, problems, such as instability of original macromolecular protein in hide glue drinks, precipitates which are easy to generate and failure due to lots of precipitates generated by mixing of protein drink and acid plant extract, are solved. According to the invention, ligustrum lucidum ait hide is extracted by an ultrasonic extraction method. Therefore, loss of anthocyanin due to long-term heating is avoided; the obtained extracting solution has better clarity, has no bad taste quality after heated; and the method is suitable for flow-line production. After mixing with a clarifying agent, purification is carried out. The purification process is simpler and cheaper than a general protein purification treatment. Macromolecules left after enzymolysis and part of tannin in the ligustrum lucidum ait extracting solution are removed at a time. The process is greatly simplified. By a low-sugar flavoring process, VC is used for protection of anthocyanin. Then, the drink has lower sugar content than an ordinary drink.

The invention relates to a method for removing endotoxin (LPS) in a phage preparation and application of the method. The method comprises the following steps: killing bacteria with chloroform, removing impurities such as bacterial fragments and the like in the phage preparation in a centrifugal mode, dissociating LPS bound to phage and degrading large molecule LPS into small molecule LPS with an active agent TritonX-100, removing free small molecule LPS by dialysis,increasing phage titer and removing large molecule LPS by PEG8000 concentration, removing introduced impurities by chloroform, andremoving an organic solvent by dialysis. The method has advantages that (1) the method has low cost and simple equipment, and can be carried out in routine laboratories; (2) LPS content in the phagepreparation is removed to be less than 5 EU / ml without affecting activity of the phage; (3) titer of active phage after recovery can reach up to 120% of that before recovery; and (4) the method has universal applicability for removal of endotoxins from phage or protein preparations.

The invention discloses a fractional degradation treatment method for plastic bags, wherein the method comprises the following five steps: S1, collecting plastic bags; S2, crushing the plastic bags; S3, soaking plastic particles; S4, degrading the plastic particles; and S5, recovering and utilizing the plastic bag raw material. According to the invention, by setting the five steps, waste plastic bags can be recycled so as to protect the environment, wherein specially through the synergistic compounding of a degradation liquid and a suspension bacterial liquid, the macromolecules of the plastics can be effectively degraded into micromolecules, so that the conveniently-degraded plastic molecules are subjected to secondary reutilization under the premise of no environment pollution so as to provide a new environment-friendly approach for white pollution treatment.

The invention belongs to the technical field of polysaccharide extraction, and particularly relates to an extraction method and application of fucoidan. The method comprises the following steps: cleaning kelp, drying, crushing, sieving, and adding composite biological enzyme for reaction to obtain enzymatic hydrolysate; inoculating probiotics into the enzymatic hydrolysate to carry out mixed fermentation, centrifuging the fermentation liquor, collecting the supernatant, and preparing fucoidan through calcium precipitation impurity removal and gradient alcohol precipitation. According to the fucoidan extraction method provided by the invention, the coupling effect of biological enzymolysis and probiotic fermentation is adopted, cell walls are cracked through the biological enzymolysis method to release internal solubles, macromolecules are degraded into micromolecules through probiotic fermentation, the extraction condition is mild, the energy consumption is low, the fucoidan extraction method is green and environment-friendly, and the efficacy performance and the product value of seaweed are greatly improved.

The invention relates to a method for degrading weathered coal with a gamma ray. At present, the development of water-soluble coal-based acid has fallen behind the production requirement and the development of new manure technology suitable for industrial production becomes urgent to meet the constantly expanded market demands. The method comprises the following step: the macromolecules in the weathered coal are degraded to water soluble micromolecules by radiating the weathered coal with the gamma ray, wherein the gamma ray is the radioisotope cobalt-60, with total dose of 50-200kGy. The method is used for degrading the weathered coal.

The invention relates to a method for treating Chinese medicinal herbs by means of microorganism transformation technology, which comprises comminuting the Job's-tears seed, placing into container, charging water so as to make it completely moistening, charging cultured rhizopus culture or enzymes produced by the rhizopus bacterium into the Job's-tears seed powder, stirring homogeneously, fermenting under the temperature of 40-100 deg. C for 4-30 hours.

The invention provides a hydrodynamic cavitation device for pharmaceutical wastewater treatment. The hydrodynamic cavitation device comprises a stator, a rotor and a rotary shaft. A cavitation cavityis formed in the stator, and a stator blind hole is distributed on the inner wall of the cavitation cavity. The rotary shaft is mounted in the rotor, one end of the rotary shaft stretches out of the stator, and the stretching-out end is connected with a transmission device. The rotor is a conical rotary disc, and is arranged in the cavitation cavity and fixedly connected to the rotary shaft, and arotor blind hole is formed in the outer wall of the rotor. A water inflow pipeline and a reagent pipeline are arranged at one end of the stator, and a water outflow pipeline is arranged at the otherend of the stator. Pharmaceutical wastewater is purified through the cavitation phenomenon, the pharmaceutical wastewater is pressed into the hydrodynamic cavitation device through pressure of a waterpump, cavitation bubbles are generated in the hydrodynamic cavitation device through mechanical rotation, by means of energy released in the generation to collapse process of the cavitation bubbles,macromolecules hardly treated in the sewage are degraded into micromolecules easily decomposed, a sufficient oxidation reaction can be carried out due to the addition of a Fenton's reagent, and the pharmaceutical wastewater is treated.

The invention discloses a method for improving the ultrafiltration membrane flux of wood acidizing fluid. The method is characterized in that a wood acidizing fluid treatment process comprises the following steps that a degradation agent is added into the wood acidizing fluid; the wood acidizing fluid is degraded into a monosaccharide solution, wherein the weight of the added degradation agent accounts for 0.05 to 0.1 percent of the weight of the wood acidizing fluid; the degradation time is 2 to 8h; the degradation temperature is 40 to 80 DEG C. The method has the advantages that the steps are simple; the operation is convenient; the wood acidizing fluid is degraded through the degradation agent, so that macromolecules such as lignin in the wood acidizing fluid are degraded into micromolecules, so that the obstruction is reduced; further, the ultrafiltration membrane flux is improved, so that the method is suitable for being popularized and used.

The invention relates to the technical field of descaling, in particular to a descaling agent and application thereof. HClO4 in the descaling agent provided by the invention can oxidize organic matters, so that organic matter macromolecules are degraded into micromolecules, and metal elements in a metal organic complex in scales are released at the same time; meanwhile, the EDTA can form a complexwith metal ions in scales and is dissolved in water; the NaF+HNO3 can dissolve Si-containing crystal substances such as SiO2 in scale substances, wherein the NaF can play a role in dissolving the silicon-containing crystal substances only in the presence of the HNO3, so that a problem that an ore bed is seriously damaged due to the fact that HF is directly used for dissolving the silicon-containing crystal substances is avoided, wherein the composite system is more gentle than a system only using HF.