Imprinted Features Research Articles

Fabrication of Nano- and Micro-Scale UV Imprint Stamp Using Diamond-Like Carbon Coating Technology

Two-dimensional (2-D) and three-dimensional (3-D) diamond-like carbon (DLC) stamps for ultraviolet nanoimprint lithography were fabricated with two methods: namely, a DLC coating process, followed by focused ion beam lithography; and two-photon polymerization patterning, followed by nanoscale-thick DLC coating. We used focused ion beam lithography to fabricate 70 nm deep lines with a width of 100 nm, as well as 70 nm deep lines with a width of 150 nm, on 100 nm thick DLC layers coated on quartz substrates. We also used two-photon polymerization patterning and a DLC coating process to successfully fabricate 200 nm wide lines, as well as 3-D rings with a diameter of 1.35 μm and a height of 1.97 μm, and a 3-D cone with a bottom diameter of 2.88 μm and a height of 1.97 μm. The wafers were successfully printed on an UV-NIL using the DLC stamps without an anti-adhesive layer. The correlation between the dimensions of the stamp's features and the corresponding imprinted features was excellent.

Imprinting mechanisms—it only takes two

Imprinted gene clusters contain multiple imprinted mRNA genes and at least one imprinted noncoding RNA (ncRNA). Two imprinted ncRNAs have now been shown to act as cis-acting domain silencers, indicating that RNA-mediated silencing may be a central feature of genomic imprinting.

Individualization of earprints : Variation in prints of monozygotic twins.

This article presents a study of the variation in the appearance of earprints from six pairs of monozygotic (MZ) twins, applying different methods with varying degrees of objectivity. By analyzing prints of MZ twins, we purposely select pairs of individuals for whom the degree of interindividual variation is low. We first provide an account of the corresponding characteristics and the differences that occur between prints from the individual members. We evaluate differences in both content (i.e., presence, shape, and intensity of imprinted features) and geometry (i.e., position of imprinted features). Differences are visualized by way of digital overlays. Differences in geometry are further evaluated by performing a hierarchical cluster analysis using variables derived from the position of seemingly corresponding features. As a next step, we explore a method to fully automatically analyze prints. In this approach, image regions are selected and matched automatically. A suggestion on how to apply this method to calculate the evidential value of an earprint is provided. To our knowledge, this is the first time that any method capable of fully automated earprint comparisons has been presented in the literature.

Mechanism of molecular recognition on molecular imprinted monolith by capillary electrochromatography

The recognition mechanism of molecularly imprinted polymer (MIP) in capillary electrochromatography (CEC) is complicated since it possesses a hybrid process, which comprises the features of chromatographic retention, electrophoretic migration and molecular imprinting. For an understanding of the molecular recognition of MIP in CEC, a monolithic MIP in a capillary with 1,1′-binaphthyl-2,2′-diamine (BNA) imprinting was prepared by in situ copolymerization of imprinted molecule, methacrylic acid and ethylene glycol dimethacrylate in porogenic solvent, a mixture of toluene-isooctane. Strong recognition ability and high column performance (theory plates was 43,000 plates/m) of BNA were achieved on this monolithic MIP in CEC mode. In addition, BNA and its structural analogue, 1,1′-bi-2, 2′-naphthol, differing in functional groups, were used as model compounds to study imprinting effect on the resultant BNA-imprinted monolithic column, a reference column without imprinting of BNA and a open capillary. The effects of organic modifier concentration, pH value of buffer, salt concentration of buffer and column temperature on the retention and recognition of two compounds were investigated. The results showed that the molecular recognition on MIP monolith in CEC mode mainly derived from imprinting cavities on BNA-imprinted polymer other than chromatographic retention and electrophoretic migration.

Selective dry etch process for step and flash imprint lithography

In order for Step and Flash Imprint Lithography (S-FIL) to be considered a viable printing technology to produce sub-100 nm geometries, a reliable pattern transfer etch process needs to be established. Unlike optical lithography processes, imprinting features via S-FIL creates a residual layer of several hundred angstroms thick, which requires a break-through etch prior to etching the transfer layer. Of greater concern is the etch barrier used as the imaging layer for S-FIL technology. The incorporated silicon content is limited to approximately nine percent, and the formulation is geared toward achieving mechanical properties for the imprinting process. As a result, typical oxygen-based plasmas used for transferring more conventional bi-layer structures are not compatible with the current S-FIL resist stack. A reducing chemistry using ammonia (NH 3) plasma has been developed in providing a selective etch process for pattern transfer using S-FIL technology. The development of this NH 3-based process was a key enabler in the fabrication of the world’s first surface acoustic wave filters patterned via S-FIL technology.

21 Centimeter Fluctuations from Cosmic Gas at High Redshifts

The relatively large Thomson optical depth, ?es, inferred recently from the WMAP observations suggests that the universe was reionized in a more complex manner than previously believed. However, the value of ?es provides only an integral constraint on the history of reionization and, by itself, cannot be used to determine the nature of the sources responsible for this transition. Here we show that the evolution of the ionization state of the intergalactic medium (IGM) at high redshifts can be measured statistically using fluctuations in 21 cm radiation from neutral hydrogen. By analogy with the mathematical description of anisotropies in the cosmic microwave background, we develop a formalism to quantify the variations in 21 cm emission as a function of both frequency and angular scale. Prior to and following reionization, fluctuations in the 21 cm signal are mediated by density perturbations in the distribution of matter. Between these epochs, pockets of gas surrounding luminous objects become ionized, producing large H II regions. These bubbles of ionized material imprint features into the 21 cm power spectrum that make it possible to distinguish them from fluctuations produced by the density perturbations. The variation of the power spectrum with frequency can be used to infer the evolution of this process. As has been emphasized previously by others, the absolute 21 cm signal from neutral gas at high redshifts is difficult to detect as a result of contamination by foreground sources. However, we argue that this source of noise can be suppressed by comparing maps closely spaced in frequency, i.e., redshift, so that 21 cm fluctuations from the IGM can be measured against a much brighter, but smoothly varying (in frequency), background.

Statistical Probes of Reionization with 21 Centimeter Tomography

We consider the degree to which 21 cm tomography of the high-redshift universe can distinguish different ionization histories. Using a new analytic model for the size distribution of H II regions that associates these ionized bubbles with large-scale galaxy overdensities, we compute the angular power spectrum and other statistical properties of the 21 cm brightness temperature during reionization. We show that the H II regions imprint features on the power spectrum that allow us to separate histories with discrete bubbles from those with partial uniform ionization (by, for example, X-rays). We also show that double reionization scenarios will modify the morphology of the bubbles in ways that depend on the mechanism through which the first generation of sources shuts off. If, for example, the transition occurs globally at a fixed redshift, the first generation imprints a persistent feature on the 21 cm power spectrum. Finally, we compare our model to one in which voids are ionized first. While the power spectra of these two models are qualitatively similar, we show that the underlying distributions of neutral hydrogen differ dramatically and suggest that other statistical tests can distinguish them. The next generation of low-frequency radio telescopes will have the sensitivity to distinguish all of these models and strongly constrain the history and morphology of reionization.

Microscopic imprints on the juvenile shells of Palaeozoic linguliform brachiopods

The juvenile shell of living discinid brachiopods is composed of valvular mosaics of rhombic, micrometric–sized siliceous tablets. The tablets are shed in adult growth stages leaving shallow imprints on the primary layer of the organophosphatic mature shell, which occur on an upper Silurian discinoid. Imprints also indent the first–formed shells of over 100 lingulate genera, including all acrotretides and Paterula. No micrometric bodies that could have made these imprints are known, but their structure and composition can be inferred from imprint morphology. Diagnostic features of imprints as casts include constancy of shape and size, and rigidity of the indenting bodies relative to the rheology of the polymerizing primary layer of chitin, glycosaminoglycans (GAGs) and apatite, in which they were embedded. Three kinds of discrete structures are distinguishable. Nanometric–sized, basinal pits that may be compound or deformed, are assumed to be casts of mucinous vesicles. Larger, flat–based and hemispherical imprints were almost certainly made by biomineralized discoids and spheroids. Additional evidence that discoids and spheroids were more soluble than apatite suggests that they were calcitic. Mineralized mosaics could have protected pelagic juveniles from solar radiation in the early Palaeozoic when the ozone layer was more rarified than today.

Characterization of and imprint results using indium tin oxide-based step and flash imprint lithography templates

As compared to quartz relief structures currently employed, indium tin oxide-based (ITO-based) step and flash imprint lithography templates offer advantages in terms of electron-beam writing, scanning electron microscope inspection, and pattern transfer. The material properties of the ITO have been completely characterized, and data is presented for resistivity, crystal structure, transmission, stress, surface roughness, adhesion, composition, and etch characteristics. For a 600 Å annealed ITO film, the resistivity is approximately 3.5×102 Ω/sq and the optical transmission 77% at 365 nm. The atomic film composition was found to be 31.5% In, 4.3% Sn, and 64.2% O by x-ray photoelectron spectroscopy. When contrasted with SiO2 films, temperature programmed desorption data suggests that hydroxyl groups on the ITO surface bind H2O less strongly but are more abundant. Ultimate verification of compatibility was obtained by imprinting features into an etch barrier layer using an ITO-based template. The fidelity of 20 nm isolated and semi-isolated features, the smallest features present on the template, was successfully reproduced via the imprinting process.

Reversal imprinting by transferring polymer from mold to substrate

A reversal imprinting technique was developed in this study. A polymer layer was first spin coated on a patterned hard mold, and then transferred to a substrate under an elevated temperature and pressure. The reversal imprinting method offers an advantage over conventional nanoimprinting by allowing imprinting onto substrates that cannot be easily spin coated, such as flexible polymer substrates. Another unique feature of reversal imprinting is that three different pattern-transfer modes can be achieved by controlling the degree of surface planarization of the mold after spin coating the polymer resist as well as the imprinting temperature. “Embossing” occurs at temperatures well above the glass transition temperature (Tg) of a polymer; “inking” occurs at temperatures around Tg with nonplanarized polymer coating surface on the mold; and “whole-layer transfer” occurs at temperatures around Tg but with a somewhat planarized surface. These three imprinting modes have been quantitatively correlated with the surface planarization of the mold after polymer coating and the imprinting temperature.

High density fluorocarbon plasma etching of new resists suitable for nano-imprint lithography

In this work, we studied etching of resists suitable for nano-imprint lithography. First, various resists have been tested in a SiO 2 process under low pressure and high plasma density conditions in order to get the best SiO 2/resist selectivity. Second, to understand resist etching mechanism and thus optimize the process, we focused our study on polymer etching behavior in different plasma conditions. Finally, transfer of imprinted features in SiO 2 has been successfully achieved.

Methylated DNA sequences in genomic imprinting.

Genomic imprinting is a special form of epigenetic system that determines the parent-of-origin-specific, or monoallelic, expression of a small number of genes, termed "imprinted" genes. Considerable sequence and methylation analysis of imprinted genes has revealed a common theme: Regions of allele-specific methylation inherited from the gametes, or primary differentially methylated regions (DMRs), are associated with CpG islands and repeat elements, and this overall structure suggests functional significance. For at least three imprinted genes the sequence of the primary DMR constitutes an element able to regulate gene activity in cis--a chromatin insulator and a promoter of an antisense transcript. In these cases the unique feature of imprinting appears to be in the ability to switch the regulatory capacity of these elements on or off by the absence or presence of inherited methylation. Increasing evidence therefore suggests that genomic imprinting for at least some genes constitutes the regulation of gene regulatory elements by methylation. An important challenge now is to determine how the differential methylation of primary DMR sequences is established in the germ line. If methylation is the primary imprint, then the processes establishing it are the primary imprinting mechanisms. Trans-acting factors that are expressed in one sex of germ line and not the other are likely to be involved, and their ability to methylate may be mediated through repeat elements associated with the sequence of primary DMRs.

Markets, hierarchies, networks, districts: A cybernetic approach

IDs are regional hyper-networks that survived the socioeconomic evolution of modern capitalism. They also promise to succeed in the coming post-Fordist development. Italian experience has shown that industrial districts are highly important, perform successfully, and are increasing their survival rates. Beyond definition problems, they are multi-dimensional, complex, and adaptive systems. They can be replicated elsewhere and, regardless of the contingent triggering factors, can grow and change their early imprinting features. Cybernetics offers a sound theoretical basis for understanding the key concepts and redirecting industrial policy interventions.

Mechanism of imprinting on mouse distal chromosome 7.

Genomic imprinting is an epigenetic mode of gene regulation that results in expression of the autosomal 'imprinted' genes from only a single allele, determined exclusively by parental origin. To date over 20 imprinted genes have been identified in mouse and man and these appear to lie in clusters in restricted regions on a subset of chromosomes. This may be a critical feature of imprinting suggesting a domain-type mode of regulation. Imprinted domains are replicated asynchronously, show sex-specific meiotic recombination frequencies and have CpG-rich regions that are differentially methylated, often associated with the imprinted genes themselves. Mouse distal chromosome 7 is one such domain, containing at least nine imprinted genes spanning over 1 Mb of DNA. For the maternally expressed p57Kip2 gene, passage through the female germline is essential to generate the active state, whereas passage through the male germline is needed to force the maternally expressed H19 gene into an inactive state. It is therefore possible that the mouse distal chromosome 7 imprinted domain is actually composed of two or more independently regulated subdomains.

Structure and function correlations at the imprinted mouse Snrpn locus.

The human SNRPN gene maps within Chromosome (Chr) 15q11-q13, the region responsible for Prader-Willi syndrome (PWS) and Angelman syndrome (AS). As one of several 15q11-q13 transcripts expressed from the paternal allele-only, SNRPN is a candidate gene to explain at least some of the PWS phenotype in human and in genetic mouse models. The promoter and first exon of the SNRPN gene also correspond to an imprinting center element responsible for resetting of the maternal to paternal imprints within 15q11-q13 during spermatogenesis. Through characterization of the imprinted murine Snrpn locus in mouse Chr 7C, we have found that the gene structure is very similar to the human, with ten conserved exons spanning 22 kb, the last seven of which are tightly clustered. The promoter of Snrpn is differentially methylated in ES cells and adult tissues, supporting a role for DNA methylation at this site in somatic establishment and/or maintenance of Snrpn imprinting. The first intron of the mouse and human genes contains structurally conserved G-rich clustered repeats which may play a role in establishing DNA methylation patterns associated with imprinting of this gene. On the basis of the conserved structural and imprinted features of the human SNRPN and mouse Snrpn genes, we suggest that imprinting mechanisms are conserved between human and mouse.

Selective recognition of malaria antigens by human serum antibodies is not genetically determined but demonstrates some features of clonal imprinting.

Malaria infection induces the production of serum antibodies to a variety of malaria antigens but the prevalence of antibodies to any particular antigen is typically much less than 100%. It has been assumed that non-responsiveness to defined antigens in malaria immune subjects is due to HLS-mediated restriction of the immune response. In this study we have investigated the role of HLA and non-HLA genes in the antibody response to two merozoite surface antigens (MSP1 and MSP2) and a sexual stage antigen (Ps260/230) of Plasmodium falciparum, and conclude that host genotype is not a major determinant of responsiveness. Although antibody levels vary in accordance with seasonal variations in malaria transmission in semi-immune children, antibody levels remain stable in clinically immune adults. Antigen recognition is selective with individual donors showing consistent high titre responses to some antigens/epitopes whilst consistently failing to recognize adjacent regions/epitopes of the same protein. An alternative explanation, consistent with the data presented here, is that selective antibody responses to malaria antigens in immune individuals result from a process akin to clonal imprinting (original antigenic sin).

Imprinting: reversal of a preference established during the critical period.

Two distinctive features of “imprinting” originally emphasized by Lorenz1 were that there was a critical period in which the preference for a particular species was established and that the preference established during this period was permanent and could not be changed by subsequent experience. These two features have been reiterated by Hess2, who has added a primacy-recency feature, claiming that the first imprinting experience has priority over a subsequent one. These features of imprinting have been questioned by Sluckin and Salzen3, who treated imprinting as a perceptual learning phenomenon in which the sensitive period is experience dependent and the stability of an imprinted preference is dependent on the amount of experience. More recent reviews by Sluckin3 and Bateson3 have supported this view. In particular the perceptual learning view of imprinting has been developed into a neuronal model hypothesis of imprinting by Salzen4 and it predicts that object preferences established by the imprinting process should be subject to reversal given sufficient exclusive and enforced experience of new objects after the end of the so-called critical period. The present experiment demonstrates a reversal of this kind.

AN EFFECT OF IMPRINTING ON THE PERCEPTUAL DEVELOPMENT OF DOMESTIC CHICKS.

SEVERAL species of bird have been found to direct their first sexual responses towards objects already familiar to them. The preferences of the birds were at least partially affected by experience occurring before sexual behaviour had matured or was artificially induced1–4. Lorenz1 argued that this long-term effect of ‘imprinting’, as the learning process has been called, is one of the criteria which distinguishes it from ‘associative learning’. At the time this view seemed justifiable since it was generally supposed that associative learning involves the attachment of a specific response to a specific stimulus. However, more recently it has been shown that an animal can use familiar cues more readily than those of which it has had no previous experience, regardless of the response which must be given5,6. This suggests that the long-term effect of imprinting on sexual behaviour is only one aspect of a more general consequence of the learning process and should not be regarded as a special feature of imprinting. The experiment described here provided preliminary evidence that birds can more easily distinguish an imprinted stimulus than unfamiliar stimuli in a situation which does not involve filial or sexual responses. The experiment made use of the finding that isolated domestic chicks (Gallus domesticus) can learn the characteristics of the pens in which they are reared7.