37 results about "Secondary growth" patented technology

The invention provides an oriented ultrathin FER zeolite molecular sieve membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, synthesizing a monodisperse FER zeolite nanosheet with a high length-depth ratio through a hydrothermal method; preparing a seed crystal liquid, and coating the surface of a porous carrier with the seed crystal liquid to form an oriented seed crystal layer; and carrying out hydrothermal epitaxial growth in a secondary growth solution. Through innovative design of seed crystal synthesis and epitaxial growth, the FER zeolite membrane prepared by the method has a structure with high alpha-axis preferred orientation, submicron controllable thickness, compactness and no defect. The membrane can be used for accurately screening gas molecules with small size difference by utilizing six-membered ring pore channels uniformly arranged along an a axis. When helium and methane or carbon dioxide are separated, the membrane shows permeation flux and separation selectivity far superior to those in the prior art, provides a brand new technical approach for efficient and low-energy-consumption recovery of helium and other high-value gases in the industry, and has great industrial application value.

The invention discloses a PagMED18 gene and application thereof in promotion of poplar growth, and relates to the technical field of plant genetic engineering, and the nucleotide sequence of the gene is as shown in SEQ ID NO.1. According to the invention, the PagMED18 gene is cloned and analyzed, and the PagMED18 gene is over-expressed in the 84K poplar in combination with an agrobacterium tumefaciens-mediated genetic transformation technology, so that the function of the gene is verified. Compared with a wild type, the plant overexpressed with the PagMED18 gene can remarkably promote the plant height, the trunk diameter and the leaf area of the poplar, and it is proved that the PagMED18 gene plays an important role in promoting the plant height and secondary growth of the poplar. The method has important practical and theoretical guiding significance for researching the growth stability of trees and cultivating new forest species.

The invention provides an SSZ-39 molecular sieve membrane and a preparation method thereof, and belongs to the field of molecular sieve membrane preparation. The molecular sieve membrane is composed of an SSZ-39 molecular sieve crystal membrane layer with a selective separation function and a supporting body playing a supporting role, and the crystal membrane layer grows on the surface of the supporting body. The synthesis process of the membrane comprises the following steps: preparing a seed crystal, loading a seed crystal layer on a support body, carrying out hydrothermal secondary growth to form the membrane and activating a de-template agent. The prepared novel SSZ-39 molecular sieve membrane has high gas separation performance, can be used for separating mixed gases such as H2 / CH4, CO2 / CH4, CO2 / N2 and N2 / CH4, and has a good application prospect.

The invention discloses a method for preparing a b-axis oriented MFI type molecular sieve separation membrane through in-situ crystallization. The method comprises the following steps: firstly, preparing a graphite transition layer on the surface of a porous carrier, then directly putting the modified porous carrier into a high-pressure synthesis kettle filled with synthesis liquid, crystallizing, washing with deionized water, and drying to obtain a b-axis oriented MFI type molecular sieve separation membrane product. According to the present invention, with the in-situ crystallization method, the seed crystal synthesis in the secondary growth method and the construction process of the carrier surface orientation seed crystal layer are avoided, the preparation process of the b-axis orientation MFI type molecular sieve membrane is simplified, and the obtained product can be used for the separation of the ethanol / water and other mixed systems, and has important application value in the actual chemical industry production field.

The invention relates to the technical field of biology, in particular to a white birch vascular cambium specific expression promoter proBpWOX4 and application of the white birch vascular cambium specific expression promoter proBpWOX4. The promoter is derived from a genome region of a betula platyphylla vascular cambium specific expression gene BpWOX4, and can accurately drive specific expression of a target gene in vascular cambium tissue cells. Specifically, after a proBpWOX4 sequence is effectively connected with a required target gene to construct a recombinant plant expression vector, the recombinant plant expression vector is introduced into a plant body, so that the expression of the target gene only in a vascular cambium can be realized. The highly spatial specific control provides a powerful tool for accurately identifying the specific function of the gene in vascular development and secondary growth, effectively avoids the interference of non-target tissues, and overcomes the bottlenecks of insufficient expression intensity, poor space-time specificity and the like of the existing promoter in forest molecular design breeding. And a key technical support is provided for cultivating excellent tree species with accelerated growth, excellent wood quality and climate adaptability.

The application discloses a preparation method of a PPSU-based ZIF-8 double-layer membrane and application of the double-layer membrane in hydrogen separation, and belongs to the technical field of gas separation membranes. The preparation method is as follows: ZIF-8 seeds are embedded in a PPSU matrix solution, then are spin-coated onto the surface of an alpha-Al2O3 carrier to obtain a PPSU-based membrane, and secondary growth of the membrane is carried out through a solvothermal reaction, so that the seeds grow epitaxially, a continuous, dense and defect-free ZIF-8 separation layer is formed on the surface and the near-surface region of the carrier substrate, and the reaction is ended to obtain the double-layer membrane. Through the seed embedding strategy, the interface bonding force between the ZIF-8 layer and the PPSU substrate is significantly enhanced, and the generation of interface defects is effectively inhibited. The double-layer membrane has high permeation flux and high separation selectivity for a H2 / CO2 system, and is particularly suitable for hydrogen separation and purification processes.

The invention discloses a method for cultivating grain-feed corn, which comprises the following steps of: selecting a grain corn variety, selecting a land and preparing the land; the method comprises the following steps: selecting corn seeds, ridging and earthing, performing single-grain precision seeding in a suitable seeding period from May 5th to May 15th, and seeding selected conventional high-grain-yield corn varieties according to the density which is increased by 5-10% compared with the recommended density of pure grains; applying a base fertilizer and a silicon-calcium-magnesium compound fertilizer at the stem position before the jointing stage, and applying a nitrogen fertilizer and a silicon-calcium fertilizer in the large bell mouth stage; green-keeping and grain-increasing fertilizer is applied 10-15 days after spinning, wherein the green-keeping and grain-increasing fertilizer comprises potash fertilizer, urea and phosphate fertilizer; from the final stage of wax ripening to the initial stage of complete ripening, when milk lines of the grains disappear or black layers are formed, the grains are harvested, and the stem and leaf structures of plants which are not completely dried up are kept to be complete; topdressing nitrogen fertilizer after harvesting, spraying growth hormone to induce differentiation of stem base regeneration buds, and harvesting the stem bases after the stem base regeneration buds grow and turn green; according to the method, the plant stem base regeneration buds are induced to differentiate, turn green and grow again, so that secondary growth and utilization of the corn straws are realized.

This utility model discloses a device for treating algae in a secondary sedimentation tank, including a track. A mounting frame is slidably mounted on the track, and a traveling mechanism is mounted on the mounting frame to drive it along the track. A connecting frame is mounted above the mounting frame, and a positioning frame is mounted on the side of the connecting frame. A cleaning component is mounted on the positioning frame, and a protective frame is located on the side of the positioning frame near the cleaning component. The protective frame is open on the side facing the track, and a collection box communicating with its inner cavity is mounted at the bottom of the protective frame. This device for treating algae in a secondary sedimentation tank uses high-pressure water flow to clean algae, achieving high cleaning efficiency and quality. It can be used for cleaning as needed, and the cleaned algae can be collected during the cleaning process to reduce algae falling and clogging the filter membrane. After high-pressure water flow cleaning, a chemical can be sprayed on the tank wall for secondary cleaning and prevention, reducing the survival rate of algae and preventing secondary growth.

The present invention provides the application of the PagGRF3a gene in promoting the secondary xylem development of trees and / or dwarfing of trees, belonging to the technical field of genetic engineering. The present invention firstly proposes that the PagGRF3a gene has the function of promoting the secondary xylem development of trees and / or dwarfing of trees. Overexpression of the PagGRF3a gene can cause the growth of trees to be retarded, the growth of secondary xylem to be advanced, the width of xylem in the stem to increase, and the ratio of the xylem area in the stem to the stem area to increase, indicating that overexpression of the PagGRF3a gene promotes the secondary xylem development and participates in the secondary growth of trees.

The invention relates to a single-power-source rotary drawing opposite cutting type paddy field weeding device. The single-power-source rotary drawing opposite cutting type paddy field weeding device comprises a rack, a driving and transmission device, a rotary disc drawing device and a rotary opposite cutting device. The rotary disc drawing device comprises a transverse moving clamping device and a rotary drawing device; the rotary bisection device comprises a bisection hooking and bearing device, a bidirectional rotary gear device and an opposite cutting device; under the driving of a single motor of the driving and transmission device, the transverse moving clamping device transversely moves to clamp weeds, the rotary drawing device synchronously rotates to draw the weeds, and the rotary disc drawing device alternately works to improve the weeding efficiency and reduce seedling damage; meanwhile, the transmission cylindrical cam drives a plurality of groups of beveled cutters to work alternately to cut up the pulled weeds so as to inhibit secondary growth of the weeds; the whole machine adopts a single-power-source design, a transmission system is simple, and efficient and high-quality weeding operation can be achieved. The invention provides a high-efficiency and low-secondary-growth-rate weeding device capable of continuously pulling and removing weeds and chopping weeds to inhibit secondary growth.

The invention discloses a method for synthesizing a hierarchical pore MFI molecular sieve membrane based on a sacrificial crystal seed layer, and belongs to the field of zeolite molecular sieve membrane synthesis. The hierarchical pore MFI molecular sieve membrane with a compact selective top layer and a macroporous transition layer with high porosity is successfully constructed on a porous carrier through a surface wet gel secondary growth technology of a sacrificial crystal seed layer. The film layer structure and the gas separation performance are optimized by regulating and controlling the composition, the aging time and the crystallization time of the synthetic gel. The prepared hierarchical pore MFI molecular sieve membrane shows high permeability and excellent selectivity in n-butane / iso-butane separation, and the preparation process is good in repeatability, high in stability and suitable for industrial gas separation application.

The invention discloses a preparation method of a shuttlecock-shaped gold nanostructure, which comprises the following steps: firstly, carrying out ultrasonic and plasma cleaning on a silicon wafer, and simultaneously preparing a triaminopropyl trioxomethylsilane solution as a coupling agent; carrying out silanization treatment on the clean silicon wafer by using a coupling agent; preparing a gold nano seed growth solution from CTAC, chloroauric acid and sodium borohydride, and self-assembling gold nano seeds on the silicon wafer treated by the coupling agent; washing redundant gold nano seeds on the silicon wafer by using ultrapure water; preparing a secondary growth solution from CTAC, chloroauric acid, ascorbic acid and cysteine, and carrying out in-situ growth. The method for preparing the SERS structure is simple, economical and convenient, and the badminton-shaped gold nanostructure can be rapidly grown on the surface of the substrate in situ.

The device comprises a machine body, a movable arm, a bucket rod, a deep digging barrel, a pushing assembly, a mowing assembly and a compacting assembly, the movable arm is movably arranged on the machine body, the bucket rod is hinged to the end of the movable arm, the deep digging barrel is connected to the end of the bucket rod, and the pushing assembly is arranged on the deep digging barrel. The pushing assembly is installed on the bucket rod and connected with the deep digging barrel, the mowing assembly is arranged at the front end of the machine body, and the compacting assembly is arranged at the rear end of the machine body. By arranging the mowing assembly, a high-speed rotating blade arranged on the mowing assembly is used for cutting plants on the earth surface and rapidly removing spartina alterniflora plants on the ground; the deep digging barrel is arranged to be combined with the inverted tassel block structure to go deep into mud flat soil, a spartina alterniflora root system is completely dug, regeneration is prevented, soil covering and compacting are conducted on a digging area through the compacting assembly, photosynthesis of residual rhizomes is blocked, and secondary growth is inhibited.

The invention belongs to the technical field of membrane separation, and relates to a method for preparing an AEI type zeolite molecular sieve membrane by a secondary growth hydrothermal method. The method comprises the steps that firstly, a prepared AEI type molecular sieve serves as a large seed crystal, a ball-milled AEI type molecular sieve serves as a small seed crystal, the AEI type molecular sieve is used for inducing growth of an AEI phase in a membrane layer, the compact AEI type zeolite membrane is prepared through a secondary hydrothermal synthesis method, and when the membrane is used for acetic acid-water separation, the separation performance is excellent. According to the method, the AEI molecular sieve is used as a seed crystal to induce the growth of the AEI membrane, the FAU molecular sieve is used for replacing traditional NaAlO2 to serve as an aluminum source, and the silicon-aluminum ratio of a membrane layer can be regulated and controlled by regulating and controlling the silicon-aluminum ratio in the membrane synthesis mother liquor. The invention provides the preparation method of the AEI type zeolite molecular sieve membrane with few defects, high density and firm combination with the carrier, and the controllable preparation of the high-performance AEI molecular sieve membrane is realized.

The invention provides a BaM seed crystal as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing and melting BaCO3, Fe2O3 and K2CO3 serving as a fluxing agent to obtain a uniform melt; the melt is subjected to heat preservation and staged cooling, seed crystals are spontaneously nucleated and grow, and initial seed crystals are obtained; the initial seed crystals are separated from the solidified melt and cleaned; and carrying out secondary growth on the cleaned initial seed crystal to obtain the BaM seed crystal. The initial seed crystal is obtained through melting and slow cooling, then the initial seed crystal is subjected to secondary growth, and finally the BaM seed crystal is obtained.

The invention discloses a preparation method of a carrier membrane, a separation material and application of the separation material, and the preparation method comprises the following steps: pretreatment of a support body; preparation of intermediate layer molecular sieve crystal seeds: stirring a structure-directing agent SDA, a silicon source and deionized water to form first sol, aging the first sol, carrying out reaction synthesis, and washing and drying the first sol to obtain intermediate layer molecular sieve crystal grains; loading of intermediate layer crystal seeds: adding dried molecular sieve crystal grains into ethanol for modification to prepare 0.5-2% (w / w) ethanol crystal seed turbid liquid, sealing two ends of the dried inorganic porous carrier, immersing the inorganic porous carrier into the turbid liquid for 10-30 seconds, then taking out the inorganic porous carrier, and drying the inorganic porous carrier in a drying oven at 80-120 DEG C for 6-12 hours; preparing a secondary growth solution; and loading a ZSM-5 membrane layer. The membrane prepared by the method is high in separation efficiency, low in energy consumption, simple to operate, long in service life and low in maintenance cost, and has a wide industrial application prospect.

The present invention relates to the field of molecular biology technology, and discloses the application of LOC7477828 gene in increasing the lignin content and S / G lignin ratio of poplar. The present invention deeply studies the potential role of LOC7477828 gene in the synthesis and secondary growth of poplar lignin. The experimental results show that the expression of LOC7477828 gene in poplar is positively correlated with the lignin content and S / G lignin ratio. By regulating the expression level of LOC7477828 gene, the lignin content and S / G lignin ratio of poplar can be effectively increased, thereby enhancing the mechanical strength and durability of poplar.

The present invention discloses the PagMED18 gene and its application in promoting the growth of poplars, and relates to the field of plant genetic engineering technology. The nucleotide sequence of the gene is shown in SEQ ID NO.1. The present invention clones and analyzes the PagMED18 gene, and overexpresses the PagMED18 gene in 84K poplars by combining Agrobacterium-mediated genetic transformation technology to verify the function of the gene. Compared with the wild type, plants overexpressing the PagMED18 gene can significantly promote the plant height, basal diameter and leaf area of ​​poplars, demonstrating the important role of the PagMED18 gene in promoting plant height and secondary growth of poplars. The present invention has important practical and theoretical guiding significance for studying the growth stability of trees and cultivating new forest varieties.

The invention relates to the technical field of plant biology, in particular to application of eucalyptus grandis EgrDof5 gene in poplar, and the application comprises at least one of the following items: a, improving poplar biomass; b, improving photosynthetic performance of the poplar; c, regulating and controlling secondary growth of the poplar; the nucleotide sequence of the eucalyptus grandis EgrDof5 gene is as shown in SEQ ID No. 1. By transferring the EgrDof5 gene into the populus genome, the poplar biomass can be increased, the photosynthetic performance of the poplar can be improved, the secondary growth of the poplar can be regulated and controlled, a new method is provided for genetic improvement of the poplar, the gene bank of the poplar can be enriched, and more choices are provided for forest breeding in the future.

The application discloses a method for synthesizing a hierarchical-pore MFI molecular sieve membrane based on a sacrifice seed layer and belongs to the field of zeolite molecular sieve membrane synthesis. The application successfully constructs a hierarchical-pore MFI molecular sieve membrane with a dense selective top layer and a macroporous transition layer with high porosity on a porous carrier through a surface wet gel secondary growth technology of a sacrifice seed layer. The membrane layer structure and gas separation performance are optimized by adjusting and controlling a synthesis gel composition, an aging time and a crystallization time. The hierarchical-pore MFI molecular sieve membrane has high permeability and excellent selectivity in n-butane / isobutane separation, has good preparation process repeatability and high stability, and is suitable for industrial gas separation application.

The application discloses application of a QmWOX4 gene in improving radial growth of Arabidopsis thaliana and belongs to the field of plant genetic engineering.The application discloses application of the QmWOX4 gene or a protein coded by the QmWOX4 gene in improving radial growth of Arabidopsis thaliana, wherein the sequence of the QmWOX4 gene is shown as SEQ ID NO:1, and the sequence of the protein coded by the QmWOX4 gene is shown as SEQ ID NO:2.It is found by the application that the QmWOX4 gene of Quercus mongolica controls radial growth of Arabidopsis thaliana, and the transgenic Arabidopsis thaliana containing the QmWOX4 gene obtained by the application has significantly improved radial growth, which is helpful to improve secondary growth of Arabidopsis thaliana, provides a reference for radial thickening and resistance enhancement of Arabidopsis thaliana, and has important scientific significance.

The invention discloses a PopA17G020368 gene and application of the PopA17G020368 gene in promoting plant growth, and relates to the technical field of plant genetic engineering, and the nucleotide sequence of the gene is as shown in SEQ ID NO: 1. According to the invention, the PopA17G020368 gene is cloned and analyzed, and the PopA17G020368 gene is over-expressed in the 84K poplar in combination with an agrobacterium tumefaciens-mediated genetic transformation technology, so that the function of the PopA17G020368 gene is verified. Compared with a wild type, the plant overexpressed with the PopA17G020368 gene can obviously promote the growth of plant height and stem diameter of the poplar. It is proved that the PopA17G020368 gene plays an important role in promoting the plant height and secondary growth of the poplar. The method has important practical and theoretical guiding significance for researching the growth stability of trees and cultivating new forest species.

The present invention discloses the Pop_A17G020368 gene and its application in promoting plant growth, which relates to the technical field of plant genetic engineering. The nucleotide sequence of the gene is shown as SEQ ID NO:1. In the present invention, through the cloning and analysis of the Pop_A17G020368 gene, and by combining the Agrobacterium-mediated genetic transformation technology to overexpress the Pop_A17G020368 gene in 84K poplar, the function of this gene was verified. Compared with the wild type, the plants overexpressing the Pop_A17G020368 gene can significantly promote the growth of the plant height and stem diameter of poplar. It is proved that the Pop_A17G020368 gene plays an important role in promoting the plant height and secondary growth of poplar. The present invention has important practical and theoretical guiding significance for studying the growth stability of trees and cultivating new varieties of forest trees.

The application discloses a gene for regulating growth and development of poplar and application thereof, and belongs to the technical field of agricultural biological genetic engineering. PagZFP12A The gene for regulating growth and development of poplar comprises PagZFP12B The nucleotide sequence of the gene is shown as SEQ ID NO:1, PagZFP12A The nucleotide sequence of the paralog gene is shown as SEQ ID NO:2. PagZFP12B The application can cause the function loss of the gene by knockout PagZFP12A and / or PagZFP12B The application can significantly promote the biomass accumulation and secondary growth of forest trees, and provides a key molecular target and technical means for improving wood yield, optimizing quality and improving stress resistance of forest trees.

The application discloses a PagMED20 gene and application thereof in promoting growth of poplar, and belongs to the technical field of cross between genetic engineering and genetic improvement of forest trees. The application verifies the function of the gene by cloning and analyzing the PagMED20 gene and overexpressing the PagMED20 gene in 84K poplar by means of agrobacterium-mediated genetic transformation technology. Compared with wild type, the plant overexpressing the PagMED20 gene can significantly promote the plant height, base diameter, net photosynthetic rate, root chlorophyll content and / or root nitrogen content of the poplar, and the important role of the PagMED20 gene in promoting the plant height and secondary growth of the poplar is proved. The application has important practical and theoretical guiding significance for studying the growth stability of trees and cultivating new varieties of forest trees.

The present invention discloses a method for preparing paraffin sections of highly lignified and highly heterogeneous materials, relating to the technical field of sectioning. The method of the present invention can be widely used to prepare paraffin sections of highly lignified and highly heterogeneous materials of different ages and species. This method overcomes the problems of cracked, curled, and incomplete sections currently encountered when preparing highly lignified and highly heterogeneous materials using paraffin sections. The sections produced by the present invention have a complete and clear structure and are highly applicable, laying the foundation for observing the secondary growth process of tree stems.

The invention discloses an acid-resistant precious metal ion adsorption film and a preparation method thereof, and the preparation method comprises the following steps: a) base film pretreatment: cleaning and drying a silicon carbide substrate to obtain a clean film; then carrying out oxidation treatment on the clean membrane to obtain a micro-oxidation membrane; finally, the micro-oxidation membrane is placed in a strong acid solution to be acidized, and a base membrane modified by hydroxyl functional groups is obtained; b) MOF seed crystal growth: placing the obtained base membrane modified by the hydroxyl functional group in a seed crystal growth solution, and reacting at 110-130 DEG C for 12-24 hours to obtain an MOF seed crystal loaded membrane; and c) secondary growth of the MOF: placing the prepared MOF seed crystal loaded membrane in a secondary growth solution, and reacting at 110-130 DEG C for 20-30 hours to obtain the acid-resistant noble metal ion adsorption membrane. The prepared adsorption film is good in acid resistance, and rare and precious metals can be efficiently and stably recycled in a strong acid environment.

The application provides a preparation method of high-purity aluminum sol with large particle size, and belongs to the field of inorganic nanometer materials. The aluminum sol seed is prepared from organic aluminum alcohol, high-purity water, an alcohol solvent and a catalyst, and is subjected to heating reflux; dropwise adding liquid prepared from organic aluminum alcohol and the alcohol solvent, and dropwise adding liquid prepared from high-purity water and the catalyst are added, so that the crude aluminum sol is obtained; the crude aluminum sol is heated, and dropwise adding liquid prepared from a chelating agent and the alcohol solvent is added, and then evaporation and solvent replacement are carried out, so that the high-purity aluminum sol with large particle size is obtained. The application realizes controllable preparation of the aluminum sol with large particle size, uniform particle size and low metal impurity content through preparation of the seed and secondary growth of the seed, and improves the average particle size and size uniformity of the sol particles.

The invention relates to a horizontally oriented ZIF-L composite film and a preparation method thereof. The membrane comprises a polyacrylonitrile (PAN) base membrane and a separation layer composed of a two-dimensional foliated material ZIF-L. The preparation method comprises the following steps: (1) synthesizing a ZIF-L material at room temperature; (2) preparing a continuously and directionally arranged ZIF-L layer on the PAN base film through an in-situ seed growth method; and (3) carrying out secondary growth treatment on the ZIF-L layer to obtain a complete separation layer. The method has the innovation points that (1) directional arrangement of the ZIF-L crystals is realized by adopting an in-situ seed growth method, and the defect of disordered growth of the ZIF-L in a traditional method is overcome; (2) the separation layer structure is optimized through a secondary growth process, and the selectivity of the membrane is remarkably improved; (3) introducing ZIF-L to construct an efficient water molecule transmission channel, and realizing hydrophilic modification of the membrane surface. The prepared pervaporation membrane shows excellent separation performance, the pure water flux can reach 4000 g.m <-2 >. H <-1 >, the separation factor reaches up to 2100, and the pervaporation membrane has good stability and pollution resistance. The membrane has wide application prospects in the fields of biofuel purification, solvent dehydration and the like.

Synthesis of crystalline CHA Zeolite powder and highly oriented defect-free CHA Zeolite membrane is described herein by the secondary growth of small pore silicoaluminophosphate powder having chabazite (CHA) type framework crystals from economic raw material Zeolite films are formed through the gradual growth and integration of individual zeolite seed crystals within a designated seed layer and through the secondary growth method by synthesizing the membrane of the zeolites using a hydrothermal process. Thereby generating defect-free membranes with improved permeance by utilizing the smaller seed crystals typically ranging from 2 to 5 μm. Ultrasound has been used to accelerate the crystallization process by enhancing mass transfer, promoting uniform nucleation, and facilitating the dispersion of precursor materials as well as to improve productivity in terms of enhanced adherence of seed crystals to support surfaces, leading to crystal quality and morphology that leads to faster synthesis times, as evidenced by the rapid generation of seed crystals.