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The identification of the printing equipment by examining only the printed product has been and will be one of the most important challenges for forensic experts who want to provide new possibilities for document examination in the fight against crime. For this purpose, the method of identifying RICOH xerographic printers was studied by examining the grids of yellow dots embeded on the printed documents. In the case of colour prints, the manufacturer of xerographic printers RICOH embed a yellow dots code that contains information that makes it possible to establish the serial number of the equipment used. [ABSTRACT FROM AUTHOR]

Rapid prototyping methods enable the widespread adoption of microfluidic technologies by empowering end-users from non-engineering disciplines to make devices using processes that are rapid, simple and inexpensive. In this work, we developed a liquid molding technique to create silicone/PDMS microfluidic devices by replica molding. To construct a liquid mold, we use inexpensive adhesive-backed paper, an acetate backing sheet, and an off-the-shelf digital cutter to create paper molds, which we then wet with predetermined amounts of water. Due to the immiscibility of water and PDMS, mold patterns can be effectively transferred onto PDMS similarly to solid molds. We demonstrate the feasibility of these wet paper molds for the fabrication of PDMS microfluidic devices and assess the influence of various process parameters on device yield and quality. This method possesses some distinct benefits compared to conventional techniques such as photolithography and 3D printing. First, we demonstrate that the shape of a channel's cross-section may be altered from rectangular to semicircular by merely modifying the wetting parameters. Second, we illustrate how electrical impedance can be utilized as a marker for inspecting mold quality and identifying defects in a non-invasive manner without using visual tools such as microscopes or cameras. As a proof-of-concept device, we created a microfluidic T-junction droplet generator to produce water droplets in mineral oil ranging in size from 1.2 µL to 75 µL. We feel that this technology is an excellent addition to the microfluidic rapid prototyping toolbox and will find several applications in biological research. [ABSTRACT FROM AUTHOR]

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The photoinduced decay of surface potential, known as xerographic discharge, is analyzed as a method of determination of photogeneration quantum yield taking into account the recombination processes. The effects of slowing down the surface potential decay with time of illumination and nonzero residual potential are usually explained by trapping of the charge carriers in the bulk of the photoconductor. However, these effects can be explained also by bimolecular recombination in the illuminated thin surface layer occurring simultaneously with the photogeneration. In this work it is assumed that as a result of the illumination the mobile positive charge carriers and immobile negative recombination centers are generated. The critical value of the recombination cross section is determined for which the nonzero residual surface potential appears. This analysis allows also to determine an influence of the accumulated recombination centers on the photocurrent decay and build up of the residual potential in a series of subsequent xerographic discharge experiments. [ABSTRACT FROM AUTHOR]

Using a dual-layered photoconductor, we have investigated the primary photocarrier generation process in x-form metal-free phthalocyanine (x-H[sub 2]Pc) over a wide range of illumination wavelengths. According to the results of quantum efficiency measurements, it has been established that the photocarrier generation mechanism in x-H[sub 2]Pc occurs via two processes: (i) production of an intermediate that depends solely on the excitation energy, and (ii) subsequent free carrier production in the presence of an electric field. In addition, the spectral quantum efficiency and the electroabsorption spectrum were measured and compared. Based on that, the primary process efficiency was divided into four regions in terms of photon energy, which explained well the relationship between them. The excitation energy dependence of the primary efficiency was semiquantitatively validated based on the electron transfer theory. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Between 1979 and 1984 São Paulo was the centre of a veritable boom in xerographic experimentation. The ardent turn to the photocopier on the part of many São Paulo-based artists was the culmination of a neo-avant-garde scene that had crystallised there since the beginning of the 1970s, during the most brutal years of the military dictatorship. Working individually, they coalesced in their appropriation of technologies of mass print media to create, in the midst of censorship and repression, dispersive and democratic works. However, these artists singularly harnessed the photocopier to simultaneously attack the parameters of canonical art and the oppressive measures of the regime that facilitated access to this very technology. This article materialises a significant and largely overlooked chapter of the conceptual turn in Brazil. It also maps a vital transition, from artists using xerography solely for its pluralising capability, to developing xerography as a visual language in its own right – reorientating the machine's function, and altering how viewers would approach these haptic works. [ABSTRACT FROM AUTHOR]

This paper suggests that xerography or copy art - also called "generative systems" - may incite melancholia. The theoretical framework for this analysis includes Svetlana Boym's concept of "broken-tech arts" (2001) and her conceptualization of ruins (2010), as well as Laura Marks' model of "haptic visuality" (2002). With the proliferation of copy machines, including Xerox, in the US in the 1960s, artists began producing new work through inventive use and creative manipulation of copiers. Copy machines allowed distinct effects, such as stretching and degeneration, and specifically resulted in the generation of haptic images: synthetic ruins that can trigger melancholia in an aesthetic experience. I posit that melancholia has the potential to inspire one to contemplate the ruined image and explore new meanings. Xerography work by Stevlana Boym, Sonia Sheridan, and Timm Ulrichs will be analyzed as relevant examples. This review contributes to melancholia studies by linking the field of xerography to the concept and experience of melancholia. [ABSTRACT FROM AUTHOR]

The role of the photoexcited state of an azo pigment as a reactant for photocarriers in a layered organic system was investigated using 2,6-anthraquinone bisazo (ABHN) or 1,4-distyrylbenzene bisazo (PDHN) pigment. Both bisazo pigments are highly sensitized by carrier transport molecules involved in the layered device. However, photocarrier generation in the bisazo pigments was quite different in the absence of sensitizing molecules; ABHN never generates, but PDHN generates to some degree by itself. The photocarriers are known to be generated via excitons of the azo pigments in the layered systems from the result of excitation-energy-independent quantum efficiencies. Electromodulated absorption spectra show that ABHN forms a Frenkel exciton and PDHN a charge-transfer-natured exciton. The different types of excitons explain the difference in carrier generation pathways of the optoelectronic systems based on these two azo pigments well. [ABSTRACT FROM AUTHOR]

Presents a study which examined the xerographic effects of small chlorine additions to amorphous selenium. Description of the discharge model; Experimental details; Results and discussion.

Presents a study which featured a complete formal solution for the kinetics of discharge of a xerographic photoreceptor. Characteristics of a photoreceptor; Mathematical representation of the photoreceptor; Equation expressing the rate of discharge; Explicit formulas for specific mobility laws.

The glass transition and non-isothermal crystallization behavior of Ge20Se70Sn10 glass prepared by the melt-quenching technique was investigated using differential scanning calorimetry (DSC) at continuous different heating rates. The structure and surface morphology of as-prepared and annealed samples were characterized using X-ray diffraction (XRD) and scanning electron microscopy. The as-prepared samples showed the amorphous glassy nature, while the annealed ones are polycrystalline. Furthermore, XRD phase analysis allowed us to find the SnSe2, GeSe2, Ge4Se9 and Sn0.5 SeGe0.5 phases in the annealed samples. According to the value of Avrami index (n), the crystallization process of studied composition has more than one crystal growth mechanism. In addition, the results of DSC showed that the investigated glass has only a single glass transition and double crystallization stages. Furthermore, the activation energy of transition as well as the crystallization has been determined based on different approximation methods. In addition, the experimental DSC data of the first and second crystallization peak were compared with that calculated with the Johnson–Mehl–Avrami and Sestak–Berggren SB(M, N) model. The results revealed that the SB(M, N) model is more suitable for describing the crystallization kinetics of studied glass. [ABSTRACT FROM AUTHOR]

Using the fact that the continuous time random walk (CTRW) scheme is a random process subordinated to a simple random walk under the operational time given by the number of steps taken by the walker up to a given time, we revisit the problem of strongly dispersive transport in disordered media, which first lead Scher and Montroll to introducing the power law waiting time distributions. Using a subordination approach permits to disentangle the complexity of the problem, separating the solution of the boundary value problem (which is solved on the level of normal diffusive transport) from the influence of the waiting times, which allows for the solution of the direct problem in the whole time domain (including short times, out of reach of the initial approach), and simplifying strongly the analysis of the inverse problem. This analysis shows that the current traces do not contain information sufficient for unique restoration of the waiting time probability densities, but define a single-parametric family of functions that can be restored, all leading to the same photocurrent forms. The members of the family have the power-law tails which differ only by a prefactor, but may look astonishingly different at their body. The same applies to the multiple trapping model, mathematically equivalent to a special limiting case of CTRW. [ABSTRACT FROM AUTHOR]

Office waste paper constitutes an excellent low cost and high quality fibre source for the papermaking industry. Limitations in the application of conventional deinking to such paper are related to negative environmental impacts chemicals can cause, hence enzymatic deinking is receiving growing attention. This study is focused on the investigation of the effect of cellulases application on the deinking of office waste paper. The methodology involved: preparation of samples, impregnation, repulping, enzymatic treatment, flotation, papermaking, and finally evaluation of optical properties. Five preparations, working under acidic and neutral conditions, were tested (Cellusoft CR, Cellusoft AP, Novozymes 342, Cellusoft L, Accelerase 1500). The added amount of each enzyme preparation corresponded to 150 FPU/100 g paper. It was observed that the deinking experiments using enzymes achieved generally better results in comparison with those in which the enzymes were previously deactivated. Despite the positive effect of activated enzymes as compared to deactivated, the application of enzymes appeared disadvantageous compared with the conventional deinking in terms of specks surface of the deinked paper sheets. Apart from the type of enzyme preparation itself, another critical factor affecting the effectiveness of the enzymatic treatment was the addition of nitric acid used to achieve acidic conditions for the optimum enzyme function. To this end, further study have to be performed on enzyme preparations functioning under alkaline conditions as well as on other paper types while the effect of enzyme amount to the deinking and the subsequent impacts on mechanical strength of produced papers may be also investigated. [ABSTRACT FROM AUTHOR]

An essay is presented which discusses the development of photocopying technology to journal aesthetics and distribution in New Zealand. The author mentions the significance of the technology in the duplication and accessibility of literature, the various technological innovations of text duplication including the inception of xerography during the 1940's, and offset printing from 1975 to 2000's

Examines a xerographic depletion discharge model describing the dark decay of the surface potential on a corona or capacitively charged amorphous semiconductor film. Dependence of the xerographic depletion time on the initial charging voltage; Effect of the energy distribution of the emission centers on the tellurium compositions; Time evolution of the surface potential on a selenium-tellurium film.

Examines the influence of charge tripping on photocarrier generation in a layered organic photoconductor consisting of a charge generation layer (CGL) and a charge transport layer by means of photoacoustic (PA) and xerographic discharge techniques. Material used by the CGL; Illustration of the typical waveforms of the PA signal.

Examines the nature of charge carrier generation from deep mobility gap states which control the dark decay of the electrostatic surface potential on a corona charged amorphous semiconductor. Information on the xerographic depletion discharge model of Melnyk and co-workers; Time dependence of the dark discharge rate; Details on the inverted depletion discharge mechanism.

In the present paper we have studied the effect of Sb addition on the optical band gap tuning of thermally evaporated Sb x Se 100-x (x = 0, 5, 20, 50 and 60) thin films. The structural investigations revealed that all thin films were amorphous in nature. Transmission spectrum was taken in the range 400–2500 nm shows that all films are highly transparent in the near infrared region. The fundamental absorption edge shifts towards longer wavelength with Sb incorporation. The optical band gap decreases with addition of antimony in a-Se thin films. A good correlation has been drawn between experimentally estimated and theoretically calculated optical band gap. The decrease in optical band gap of thin films has been explained using chemical bond approach and density of states model. Decrease in optical band gap with Sb addition increases the concentration of electron deep traps which increases the X-ray sensitivity of Sb-Se thin films. Thus by tuning the optical band gap of Sb-Se alloy, it could be utilized for xerographic based applications. [ABSTRACT FROM AUTHOR]

In many real-world commercial applications, such as electrophotographic printing, the adsorption of water on critical surfaces has an overwhelming but poorly understood effect on the desired materials performance. This work is focussed to better understand the effect of water on the triboelectric charge transfer between surfaces in xerography. Molecular mechanics was used to find the most probably water adsorption sites for isolated polymethylmethacryate (PMMA) and isolated silica models, and for intermolecular complexes between PMMA and silica which are responsible for triboelectric charge transfer. Density functional theory (DFT) was used calculate the local energy minima, the adsorption of water molecules on different surface functional groups, and the analysis of the frontier orbitals, to quantitatively compare the energy gap differences for electronic charge transfer, and thus the effect of the hydration site on PMMA and silica on electronic charge transfer. Four ways were found for surface water adsorption to affect the electronic charge transfer between PMMA and silica: (1) adsorption of a water molecule on the carbonyl group of PMMA decreases the energy level o f the highest occupied molecular orbital (HOMO) on PMMA, thus making electron charge transfer more difficult because of the transfer barrier increase; (2) a water molecule acts as part of the electron accepter when adsorbed at the active site of the lowest unoccupied molecular orbital (LUMO) on silica, which lowers the LUMO and thus lowers the charge transfer barrier, but at the same time creates a charge dissipation pathway as a part of the charge transfer is now to water, rather than to silica; (3) a water molecule acts as a spacer between PMMA and silica, which increases the energy gap for charge transfer and thus decreases the charge transfer; and (4) water molecules can act as a charge carrier, dissipating electrons by accepting charge when adsorbed on silica and then donating back charge when adsorbed on PMMA. This work provides a detailed mechanistic understanding of the effects of water on the surface electronic structure of amorphous silica and PMMA that are critical to electrophotographic applications, and no doubt to other applications where the surface electronic structure is relevant. [ABSTRACT FROM AUTHOR]

During xerographic printing processes, the electric charge properties of the paper surface are essential to obtain effective toner transfer and high image quality. Surface and volume resistance are indispensable to the accumulation of the surface charge and different resistance values generate different electrical fields with optical drum, and have a significant effect on toner transfer efficiency. In this paper, surface sizing was investigated to improve the surface properties for better toner transfer and image quality. Styrene acrylate emulsion (SAE) latex was successfully synthesized and fully characterized with a Fourier transform infrared (FT-IR) spectrometer, a laser particle analyzer and a scanning electron microscope (SEM). The results showed that under the conditions of emulsifier dosage at 3 wt%, initiator concentration at 0.5 wt% and the reaction temperature at 80°C, the monomer conversion can reach 80%. The effects of various factors including initiator dosage, emulsifier dosage and monomer ratio on the sizing performance were studied. The effects of different ratios of SAE to starch on surface and volume resistance of paper were also systematically investigated. The differences in electric properties of various paper samples were quantified and their influence on paper-toner adhesion and print quality was clarified. Relationships between electrical properties of paper and paper-toner adhesion force, and thus print quality were established. Strategies to improve printing performance through effective control of paper electrical properties were also developed. It is concluded that the best printing quality and toner adhesion were achieved when the ratio of SAE to starch is between 1:10 and 2:10. [ABSTRACT FROM AUTHOR]

Two efficient phase-transfer-catalyzed protocols for the diastereoselective synthesis of cis and trans isomers of 2,6-diaryltetrahydrothiopyran-4-ones (2,6-DATHTPs) have been developed. In a study of the scope of the reactions, differently substituted 2,6-DATHTPs were successfully accessed in high yields and diastereomeric excessses on both experimental and preparative scales. [ABSTRACT FROM AUTHOR]

This article examines the impact of copy machines on late twentieth-century print cultures. Specifically, this article makes a case for “dry copying,” the method of print reproduction perfected by Xerox in the late 1950s, as a unique medium rather than a weak imitation of other printing methods. Following the claim that the widespread availability of copy machines in the late twentieth century represented the arrival of a new medium, this article further examines how understandings of authorship, established with print culture, came undone in the era of the copy machine. Finally, this paper makes a case for understanding copy machines as a form of “social media” that opened up opportunities for writers, readers and publishers to create, share, exchange and comment on texts and images in communities and networks of their own making in the decades preceding the development of the web.

This article examines the impact of copy machines on late twentieth-century print cultures. Specifically, this article makes a case for “dry copying,” the method of print reproduction perfected by Xerox in the late 1950s, as a unique medium rather than a weak imitation of other printing methods. Following the claim that the widespread availability of copy machines in the late twentieth century represented the arrival of a new medium, this article further examines how understandings of authorship, established with print culture, came undone in the era of the copy machine. Finally, this paper makes a case for understanding copy machines as a form of “social media” that opened up opportunities for writers, readers and publishers to create, share, exchange and comment on texts and images in communities and networks of their own making in the decades preceding the development of the web.