Master Plate Research Articles

Nano-patterned Medium Fabricated by the Artificially Aligned Self-Assembling Method

A new method for fabricating a patterned magnetic recording medium is presented. This method uses the self-assembling phenomenon of the diblock copolymer. A tetragonal array of ordered polymer dots is aligned by a circumferential groove pattern on a disk substrate. The groove pattern is transferred from a Ni master plate by a nanoimprinting process. CoCrPt patterned media with a dot pattern were fabricated using this method (artificially aligned self-assembling (AASA) method). The dot size was about 40 nm in diameter. Magnetic estimations showed the single-domain CoCrPt dots with good magnetic isolation. The patterned medium showed a perpendicular magnetic orientation induced by the crystalline anisotropy. TEM observation revealed little physical damage in CoCrPt dots though an ion milling process was employed for etching the magnetic layer. Degradation in the magnetic anisotropy energy was also found to be slight by the estimation with a micromagnetic simulation. A master plate with the AASA pattern has been developed. This removes the annealing process from the fabrication process and improves the throughput. Pattern transfer of the AASA master into the photopolymer layer was successful.

Fabrication of hologram coins using electron beam lithography

Diffractive grating structures formed by electron beam lithography have been replicated into the surface of silver commemorative coins. The detailed features of the gratings and the depth of relief were accurately transferred from the resist master plate to the surface of the fine silver coins using a Ni shim as a replication tool. This method has produced an optically variable device (OVD) in the surface of the coins which exhibited a strong intensity of first-order diffraction over the area of the image (3 × 1.5 cm). A feature of the grating structures formed in the coins were fine-scale protrusions located along the length of the ridges. The presence of these protrusions has been attributed to an adhesive transfer and back-transfer of Ag during the cycle of impact loading of the Ni shim for sequential coins.

Fabrication of Hologram Coins using Electron Beam Lithography

AbstractDiffractive grating structures formed by electron beam lithography have been replicated into the surface of silver commemorative coins. The detailed features of the gratings and the depth of relief were accurately transferred from the resist master plate to the surface of the fine silver coins using a Ni shim as a replication tool. This method has produced an optically variable device (OVD) in the surface of the coins which exhibited a strong intensity of first order diffraction over the area of the image (3 × 1.5 cm). A feature of the grating structures formed in the coins were fine-scale protrusions located along the length of the ridges. The presence of these protrusions has been attributed to an adhesive transfer and back-transfer of Ag during the cycle of impact loading of the Ni shim for sequential coins.

A simple method for screening bacterial colonies for mutagenized sites in plasmid DNA

Because of the multiple-step process that is involved in the detection of mutagenized restriction enzyme sites in plasmid DNA, a simple and accurate method was developed to analyse the plasmid DNA of site-directed mutagenesis experiments from bacterial colonies. The desired mutated part is located between the Eco RI restriction site on pUC19. Two mutagenic primers were designed to replace only one nucleotide on segments A and B of the bi-segmented genome of infectious bursal disease virus (IBDV). Two restriction sites were created for those mutations in each segment, Fsp I and Dra I, respectively. Following a protocol from the site-directed mutagenesis kit, the mutated plasmids were used to transform, and were propagated and maintained in DH5 alpha competent cells. Colonies were picked from the master plate, and used as DNA template for PCR. The PCR technique included the design of two pairs of primers, one for each segment, which were to amplify a region up to 1000 bp. Samples were pre-incubated for 3 min at 94 °C to induce bacterial lysis before starting the nucleic acid amplification. The PCR products 918 bp from segment A and 650 bp from segment B were digested with Fsp I and Dra I at 37 °C for 1 h. Products were resolved on 0.9% agarose gel which contained ethidium bromide. This method is simpler, faster and more accurate than the traditional method of mini-prep plasmid isolation and colony blot hybridization to identify the mutated plasmids.

Rainbow holographic camera

A rainbow holographic camera system is presented. The system uses only a single laser beam for recording, so an antivibration arrangement is not required. The slit effect of the rainbow hologram is generated by replication from the slit master plate. Clear three-dimensional images have been sucessfully recorded by the system. The system is also useful for holographic interferometery.

Evaluation of defects on an optical disc master plate

This paper presents a method to analyse and detect defects on the surface of a master disc (the cause of distorted images) by applying a neural network program and micro-image technology. The method automatically, step-by-step, detects defects in the disc’s electrical signal output which drives an x– y table and provides indicative information for managing contamination in a cleanroom of a manufacturing plant.

Vibration of a master plate with attached masses using modal sampling method

At medium frequencies, several problems deal with systems having a large number of modes where classical modal methods must cope with the solution of large linear systems. The objective of the modal sampling method is to reduce these systems of equations in order to obtain a simplified model. The vibration response of a structure is reconstructed using a limited number of modes, called a sample, to interpolate the response of other modes. The accuracy of the prediction can be improved by increasing the size of the sample. The method, which has been developed in the case of a long beam, is presented here in the case of a nonhomogeneous structure such as a large, thin plate where point masses have been added. The structure is excited by a harmonic point force or a planar acoustic wave. A study of the convergence of the method shows that global quantities such as space—and/or frequency—averaged energy converge quickly. Thus predictions can be obtained with models having few degrees-of-freedom. Moreover, results show the ability of the method to take into account a master plate with attached point mass heterogeneities.

Prediction of vibrations using a wave sampling decomposition

At medium frequency range (MFR), numerous vibroacoustic problems deal with systems of large number of modes where classical modal methods must cope with resolution of huge linear systems. In the idea of reducing these models, a mode hybridization method [H. J-P. Morand, ‘‘A modal hybridization method for the reduction of dynamic models in the medium frequency range,’’ Proceedings of the European Conference on New Advances in Computational Structural Mechanics (1991)] gives one equivalent mode obtained with modes of the complex structure. Another method [D. Trentin and J. L. Guyader, ‘‘Vibrations of a master plate with attached masses using modal sampling method,’’ J. Acoust. Soc. Am. (to be published)] based on reducing size of dynamic model in the MFR, gives a prediction of the vibration response of a structure by using a limited number of modes of the homogeneous master structure in order to interpolate the response of modes of whole structure with attached heterogeneities. The method presented here gives a prediction of plate vibration using a wave decomposition instead of modal calculation. The corresponding wave function of the Fourier transform of the displacement is approximated the best by achieving the extremalization of the Hamiltonian of the plate. Quadratic velocity of the structure is derived and the convergence study of the method shows that global quantities involving frequency average can be obtained with reduced models of small size. [Work supported by the Institut National de Recherche et de Sécurité and by the Centre National d’Etudes Spatiales.]

Spontaneous revertants in modified S. typhimurium mutagenicity tests employing elevated numbers of the tester strain

It has been proposed that increases in the number of bacteria applied to each plate can enhance the sensitivity of the Ames S. typhimurium mutagenicity assay. These procedures have the potential to elevate the number of spontaneous revertants (SR) by increasing the contribution of pre-existing revertants (PER) present before application of the bacteria to the limited histidine test plates. We have investigated the contribution of PER when 10 9 bacteria are applied to the plates and found that the number of PER is dependent on the handling and storage of the cultures used to inoculate the overnight broth. The average number of PER/10 9 viable bacteria after overnight growth in broths inoculated from a frozen permanent, lyophilized permanent, master plate, and an isolated colony, of TA98 were 267, 188, 57 and 13 respectively. The resultant elevation of the number of SR for a strain may result in a failure to identify a mutagenic response. It is recommended that the number of PER be monitored in any modification of the Ames test that makes use of elevated numbers of bacteria.

Paper replication method for isolation of radiation-sensitive mutants.

A filter paper replication system particularly useful for isolation of radiation-sensitive mutants of pigmented bacteria was devised. The fidelity of replication was high. Adhesion between a paper disk and a properly dried master plate provided adequate contact pressure. The replicas arising from this technique constitute a convenient apparatus for general application in isolation of clones sensitive to a discriminating treatment.

Isolation of Chinese hamster ovary cells with reduced unscheduled DNA synthesis after UV irradiation.

A simple procedure has been worked out to obtain UV-sensitive mutants of Chinese hamster ovary (CHO) cells. In this procedure, conventional mutagenesis is followed by BrdU--light treatment to enrich the population for UV-sensitive cells. Colonies that are allowed to form subsequently are duplicated by replica plating and screened on the master plate for their UV sensitivity and their capacity to carry out UV-induced DNA repair synthesis. Putative mutants are isolated from the replica. With this combination of methods, we succeeded in isolating CHO mutants with an 85-95% reduced level of UV-induced DNA synthesis in combination with an increased UV sensitivity.

TECHNIQUES AND MARKER GENES FOR USE IN MACROCYST GENETICS WITH POLYSPHONDYLIUM PALLIDUM

Previous work has shown that genetic exchange occurs in the macrocyst of Polysphondylium pallidum, as in species of Dictyostelium. These studies are extended here. Mutants resistant to six different poisons have been isolated for use as genetic markers. A replica-plating technique has been engineered whereby 14 progeny clones growing on a master plate may be simultaneously transferred to test plates containing individual poisons. Germination percent of macrocysts has been greatly increased by the presence of a growing fungus during the resting stage. These means have been used to analyze crosses showing that: (1) Vegetative amebae are haploid, at least at the three marker loci tested. (2) Amebae emerging from a single macrocyst are identical about 90% of the time. (3) Any single combination of parental markers may emerge from a given macrocyst, and all combinations appear in approximately equal frequencies. These findings suggest that normally one of four nuclei produced by meiosis survives in every macrocyst and that all markers examined are unlinked. (4) About 10% of the macrocysts germinate to give two or more classes of progeny. These may result from the presence of a second zygote in the macrocyst or from the survival of two nuclei after meiosis. (5) If genetic exchange occurs during spore formation or microcyst formation, its frequency is low (<0.01%).

Affinity filters, a new approach to the isolation of tox mutants of Vibrio cholerae.

We have devised a novel plate assay method for detecting mutants of Vibrio cholerae altered in the production of cholera toxin (tox mutants). Colonies replicated from a master plate are grown on the surface of a cellulose filter disc to which ganglioside-albumin conjugates have been attached. Toxin secreted by the colonies is tightly bound to the ganglioside filters. After removal of the cells by washing, the bound toxin may be detected by treating the filters with radioactively labeled antibodies against either whole toxin or one of its constituent polypeptide chains, followed by autoradiography. Colonies producing significantly greater of lesser amounts of toxin than the parental type are easily recognized and can be shown in liquid culture to have the corresponding hypertoxinogenic or hypotoxinogenic phenotype. This method, termed "the ganglioside filter assay," is applicable to screening large numbers of colonies and should facilitate isolation of various specific classes of mutants in cholera toxin production. In modified form the method will be applicable to various systems in which mutants of secreted proteins are sought.

An all-metal block for replica plating of microbial colonies

The surface of a metal block made of an aluminium alloy is covered with narrow perpendicular grooves, which thus form an array of quadrangular pyramids touching base to base. The surface is further provided with a marker which assures the positioning of the master plate and the replica plate. Replicas prepared using this block are of higher quality than those using the velveteen-covered cylinder. A single master plate will provide ten or more replicas of good quality, the master plate being preserved for further work. Last but not least, the all-metal block can be easily cleaned and heat-sterilized.

Video disc mastering and replication

The mastering and replication of video discs is described. Mastering involves exposing a photoresist-coated plate to a focused, modulated laser beam. After development, a layer of nickel is grown on the photoresist surface. The nickel layer forms a negative copy of the master plate. This nickel copy may then be used to emboss into plastic sheet a positive replica of the original master. This paper emphasizes the critical parameters involved in the process.

A Replica Plating Method for Plant Cells

AbstractA replica plating method is described for plant cells growing in Petri dishes. The method involved a uniform application of plant cells (Morinda citrifolia L.) by spraying cells evenly on agar plates containing 60% conditioned medium. Subsequently the cells were allowed to grow through a nylon net. The net was removed from the master plate and placed upside down on replica plates. Cells from colonies adhering to the threads of the net were thus transferred to the replica plate and yielded colonies that, after a growth period of about 10–20 days, corresponded in position to the colonies on the master plate. An 80% transfer of colonies from the master plate to the copy plate was possible.

Isolation of Escherichia coli mutants defective in enzymes of membrane lipid synthesis.

A new method has been developed which permits the rapid screening of E. coli colonies for mutants with defective enzymes of phospholipid metabolism. In this procedure, a disc of filter paper is pressed down on an agar plate containing several hundred colonies of mutagen-treated cells, after which the paper is lifted off. In the process the colonies are transferred to the paper, giving rise to a replica print of the master plate. The few cells from each colony left on the master keep growing in the original pattern. The pattern of colonies is also retained on the filter paper, even after the cells are rendered permeable with lysozyme and EDTA. Colonies treated in this manner remain absorbed to the paper, where they can convert sn-(U-14-C)glycero-3-P to phosphatidyl(U-14-C)glycerophosphate, dependent on added CDP-diglyceride. Unrelated reactions of sn-(U-14-C)glycero-3-P that may obscure the synthesis of phosphatidyl-glycerophosphate are inhibited by the addition of reagents poisoning energy generation. The radioactive phospholipid that forms around each colony on the paper is precipitated in situ with trichloroacetic acid, and unreacted sn-(U-14-C)glycero-3-P is washed away. After autoradiography, the colonies on the filter paper are stained with Coomassie blue. When the autoradiogram is superimposed on the strained paper, mutants are identified as blue colonies lacking a black halo. With this method, 20,000 colonies were screened in several days. Four mutants were identified with low levels of CDP-diglyceride:snglycero-3-P phosphatidyl transferase (EC 2.7.8.5, GLYCEROL-PHOSPHATE PHOSPHATIDYLTRANSFERASE, PHOSPHATIDYLGLYCEROPHOSPHATE SYNTHETASE) IN EXTRACTS. With a similar assay, 10,000 additional colonies were screened for mutants with altered CDP-diglyceride:L-serine O-phosphatidyltransferase (EC 2.7.8.8, phosphatidylserine synthetase), and four strains were found in which the enzyme is thermolabile. The screening technique described here is termed replica printing and should be applicable not only to studies of phospholipid metabolism but also to nucleic acid and protein synthesis.

A Fast Turn Around Electron-Beam Pattern Generation System

An electron-beam mask-generation system designed to demonstrate fast turn around and high resolution capability is described. The system has been developed using an Advanced Metals Research 900 SEM and a Nuclear Data 812 computer. Patterns are generated utilizing a matrix of 4096×4096 randomly addressable data points. Complex and/or large patterns can be generated by mechanical repositioning of the substrate and scanning of adjacent fields. A complete stepped and repeated master plate is produced in several hours as compared with several days using conventional systems. The time saving has been primarily achieved by combining the artwork generation, reduction, and step and repeat operations into a single operation. Compatibiltiy with conventional computer aided design and graphics software has been maintained by translating ordinary artwork generation data into information acceptable by the electron-beam system. Extensive software allows virtually all geometries to be generated by the system.

Colony formation of mammalian cells on agar plates and its application to Lederberg's replica plating

In this paper we describe a new technique of cloning by use of agar plates and its application to replica plating. It was found that most cell lines form colonies on the surface of solid agar, although the plating efficiency and size of colony is dependent on specimens and concentrations of agar and agarose used. When 0.5% Noble-agar was used as substrate, plating efficiencies were obtained comparable to those of conventional cloning techniques in liquid medium and of agar suspension cultures. In some cases, including the primary culture of Yoshida sarcoma, the efficiency of plating was apparently higher than that obtained by the already established procedures. In an experiment with a series of BHK-21 cells, it was found that virally transformed cells could form colonies on agar plate, whereas untransformed and reverted cells could not divide, suggesting that agar plate culture, as well as agar suspension culture, can be used for a selective assay of transformation. Two methods of replica plating were employed. Method I is that devised by Lederberg in which colonies on the master plate are imprinted on pile fabrics and then transferred to the replica plates. With FM3A cells, the fidelity of replica plating was around 95%. Method II is inoculation of clones by applying a glass rod to the replica plates on which positions of inocula were identified by a grid. Fidelity of replica plating of FM3A, L5178Y and YSC cells was 99.7, 100 and 100% respectively.

A technique for replica platingCoprinus lagopus, a filamentous fungus

SUMMARYThe problem of replica plating filamentous fungi such asCoprinus lagopusis overcome by inducing micro-colonies with sodium deoxycholate and using ‘Velcro’, a hooked material, to replace velveteen in the standard replica plating technique. ‘Velcro’ is advantageous in that it has a regular pattern of closely spaced hooks which transfer small inocula from the colonies on the master plate.