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This work describes a novel rapid method to fabricate high-resolution paper-based microfluidic devices using wax-ink-based printing. This study demonstrates that both temperature and pressure are important knobs in controlling the device resolution. High-resolution lines and patterns were obtained by heating the paper asymmetrically from one side up to 110 °C while applying pressure up to 49 kPa. Starting with wax lines with an initial width of 130 μm, we achieve a thorough penetration through a 190 μm-thick paper with lateral spreading on the front as narrow as 90 μm. The role of temperature and pressure are systematically studied and compared with the prediction of the Lucas-Washburn equation. We found that the temperature dependence of spreading can be explained by the viscosity change of the wax, according to the Lucas-Washburn equation. The pressure dependence deviates from Lucas-Washburn behavior because of compression of the paper. An optimal condition for achieving full depth penetration of the wax yet minimizing lateral spreading is suggested after exploring various parameters including temperature, pressure, and paper type. These findings could lead to a rapid roll-to-roll fabrication of high-resolution paper-based diagnostic devices. [ABSTRACT FROM AUTHOR]

A simple, reliable, and low-cost fabrication method is proposed here for assembling paper-based electrochemical devices (PEDs) using a commercial desktop digitally controlled plotter/cutter, together with ordinary writing tools. Permanent markers (tips of 1 mm) were used to create effective hydrophobic barriers on paper, while micromechanical pencils (mounting 4B graphite leads, 0.5 mm in diameter) were adopted for automatically drawn precise reference, counter, and working carbon electrodes. Fabrication parameters, such as writing pressure and speed, were first optimized, and the electrochemical performance of these devices was then evaluated by using potassium hexacyanoferrate(II) as redox probe. The good interdevice reproducibility (4.8%) displayed by the relevant voltammetric responses confirmed that this strategy can be profitably adopted to easily assemble paper-based electrochemical devices in a highly flexible manner. The simplicity of the instrumentation used and the low cost of each single device (about $0.04), together with the speed of fabrication (about 2 min), are other important features of the proposed strategy. Finally, to confirm the effectiveness of this prototyping method for the analysis of real samples and rapid controls, PEDs assembled by this simple approach were successfully exploited for the analysis of vitamin B6 in food supplements. [ABSTRACT FROM AUTHOR]

Infectious diseases are a major global health issue. Diagnosis is a critical first step in effectively managing their spread. Paper-based microfluidic diagnostics first emerged in 2007 as a low-cost alternative to conventional laboratory testing, with the goal of improving accessibility to medical diagnostics in developing countries. In this review, we examine the advances in paper-based microfluidic diagnostics for medical diagnosis in the context of global health from 2007 to 2016. The theory of fluid transport in paper is first presented. The next section examines the strategies that have been employed to control fluid and analyte transport in paper-based assays. Tasks such as mixing, timing, and sequential fluid delivery have been achieved in paper and have enabled analytical capabilities comparable to those of conventional laboratory methods. The following section examines paper-based sample processing and analysis. The most impactful advancement here has been the translation of nucleic acid analysis to a paper-based format. Smartphone-based analysis is another exciting development with potential for wide dissemination. The last core section of the review highlights emerging health applications, such as male fertility testing and wearable diagnostics. We conclude the review with the future outlook, remaining challenges, and emerging opportunities. [ABSTRACT FROM AUTHOR]

The hybrid films of reinforcing the aged papers have been employed via layer-by-layer (LBL) assembly deposition of the chitosan lactate/carboxymethyl cellulose complex previously modified with metal oxide. In order to reinforce the films, a vacuum infiltration was adopted in the LBL process. The mechanical properties and structure of the aged papers in relation to fiber morphology were investigated using SEM, FTIR, XPS, and tensile test. The well-dispersed coatings resulted in an excellent improvement in mechanical properties of the modified paper. After only three bilayers deposited, the measured tensile strength and folding endurance for modified aged newspaper samples increased up to 100% and 450%, respectively, as compared to the control sample. This high efficiency was kept even when the modified paper samples exposed to the moist-heat accelerated aging and UV irradiation. The pH of the paper rose to alkalescence rapidly, and the paper samples maintained their coloration close to the original after treatment. [ABSTRACT FROM AUTHOR]

The occurrence of fluorotelomer alcohols (FTOHs) was investigated in 94 food-contact materials (FCMs). We detected 6:2 FTOH (<0.60--1110 ng/g), 8:2 FTOH (<0.40--8490 ng/g), and 10:2 FTOH (<0.02--9350 ng/g) in most FCM samples, and four longer-chain C14-20 FTOHs were, for the first time, identified in FCMs with relatively high concentrations (<0.02--8450 ng/g for 12:2 FTOH, <0.02--1640 ng/g for 14:2 FTOH, <0.02--372 ng/g for 16:2 FTOH, and <0.02--130 ng/g for 18:2 FTOH). There were three typical profiles of FTOHs that were dominated by 6:2 FTOH (95.6 ± 8.1% in 9 FCMs), 8:2 FTOH (50.9 ± 20.8% in 22 FCMs), and 10:2 FTOH (44.5 ± 20.9% in 30 FCMs), indicating the congener-specific usage of FTOHs for different commercial purposes. All nine detectable FCMs produced in the United States were dominated by 6:2 FTOH, which was significantly different from those produced in China. The median concentration of total FTOHs in eco-friendly paper tableware was 2990 ng/g, which was lower than in popcorn bags (18 200 ng/g) but much higher than other FCMs (<0.55--38.7 ng/g). FTOHs could migrate from paper bowls, with migration efficiencies of 0.004--0.24% into water, 0.004--0.24% into 10% ethanol, 0.009--2.79% into 30% ethanol, 0.06--13.0% into 50% ethanol (v/v) simulants, and 0.04--2.28% into oil. Migration efficiencies decreased with increasing carbon chain lengths of FTOHs. [ABSTRACT FROM AUTHOR]

Paper is an extraordinary example of a composite engineering material with practical use in a huge variety of applications. Since its invention in China, there have been many alterations to manufacturing techniques, component formulation, and surface finishing, yet the essential characteristics of paper have not changed greatly. The objective of this experiment is to demonstrate that the chromatographic performance of paper as a stationary phase may be used to distinguish between externally similar materials. The procedure developed is so simple that even students with little exposure to practical chemistry and limited chemical knowledge can understand the essential content. Because of the ubiquitous nature of paper, it is often recovered from crime scenes as evidence for analysis. However, the variety of sources and the mechanical or chemical properties often make demonstration of unequivocal correlation between "questioned" and "known" or "reference" samples a complex task. Introducing the practical session as a crime scene investigation, and presenting the laboratory exercise as an accessible forensic technique for paper identification, adds an exciting dimension to the practical experience for young people. The authors' application of this strategy has been successfully extended as it has become evident that the experiment motivates a surprisingly wide range of audiences. [ABSTRACT FROM AUTHOR]

Inorganicfillers, the second largest component of the papermakingprocess, have poor bondability with cellulosic fibers, interfere ininterfiber bonding, and reduce paper strength. Filler preflocculation/modificationis a practical method for enhancing interactions between the fillerparticles and fibers. This article reports on the effects of fillercontent and preflocculation on the filler bondability factor calculatedbased on first-pass ash retention and paper strength properties suchas the tensile, Z-direction tensile, and compositetensile indexes. Talc filler preflocculated using 0.1–0.8%dosages of cooked cationic starch based on the dry weight of fillerwas loaded in paper to obtain varying filler contents of 15–24%.The filler bondability factor (FBF) and various tensile propertiesof paper were calculated and analyzed for all experiments. FBF andpaper strength were reduced with increasing filler content in paper,whereas they were improved upon addition of preflocculated fillerin paper. Noticeably, preflocculated filler resulted in increasesin FBF and composite tensile index of 13–24% and 7–15%,respectively, at a 24% filler content in paper. [ABSTRACT FROM AUTHOR]

We demonstrate the hybridization-induced fluorescence detection of DNA on an origami-based paper analytical device (oPAD). The paper substrate was patterned by wax printing and controlled heating to construct hydrophilic channels and hydrophobic barriers in a three-dimensional fashion. A competitive assay was developed where the analyte, a single-stranded DNA (ssDNA), and a quencherlabeled ssDNA competed for hybridization with a fluorophorelabeled ssDNA probe. Upon hybridization of the analyte with the fluorophore-labeled ssDNA, a linear response of fluorescence vs analyte concentration was observed with an extrapolated limit of detection <5 nM and a sensitivity relative standard deviation as low as 3%. The oPAD setup was also tested against OR/AND logic gates, proving to be successful in both detection systems. [ABSTRACT FROM AUTHOR]

We present a microfluidic paper analytical device (μPAD) that relies on flow in hollow channels, rather than through a cellulose network, to transport fluids. The flow rate in hollow channels is 7 times higher than in regular paper channels and can be conveniently controlled from 0 to several mm/s by balancing capillary and pressure forces. More importantly, the pressure of a single drop of liquid (0.2 mbar) is sufficient to induce fast pressure-driven flow, making hollow channels suitable for point of care diagnostics. We demonstrate their utility for simple colorimetric glucose and BSA assays in which the time for liquid transport is reduced by a factor of 4 compared to normal cellulose channels. [ABSTRACT FROM AUTHOR]

We report a plasmonic paper-based analytical platform with functional versatility and subattomolar (<10-18 M) detection limit using surface-enhanced Raman scattering as a transduction method. The microfluidic paper-based analytical device (μPAD) is made with a lithography-free process by a simple cut and drop method. Complex samples are separated by a surface chemical gradient created by differential polyelectrolyte coating of the paper. The μPAD with a starlike shape is designed to enable liquid handling by lateral flow without microchannel patterning. This design generates a rapid capillary-driven flow capable of dragging liquid samples as well as gold nanorods into a single cellulose microfiber, thereby providing an extremely preconcentrated and optically active detection spot. [ABSTRACT FROM AUTHOR]

A low cost, microfluidic paper electrochemical device (μPED) was fabricated using screen printing of electrodes and heat transfer of patterned wax paper onto filter paper. The μPED features films of a light-emitting ruthenium metallopolymer, microsomal metabolic enzymes, and DNA to detect potential genotoxic pollutant activity in environmental samples. Unlike conventional analytical methods that detect specific pollutant compounds, the μPED was designed to rapidly measure the presence of genotoxic equivalents in environmental samples with the signal related to benzo[a]pyrene (B[a]P) as a reference standard. The analytical end point is the detection of DNA damage from metabolites produced in the device using an electrochemiluminescence output measured with a charge-coupled device (CCD) camera. Proof-of-concept of this measurement was established for smoke, water, and food samples. The μPED provides a rapid screening tool for on-site environmental monitoring that specifically monitors the genotoxic reactivity of metabolites of toxic compounds present in the samples. [ABSTRACT FROM AUTHOR]

A paper-based solid-phase assay is presented for transduction of nucleic acid hybridization using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). The surface of paper was modified with imidazole groups to immobilize QD-probe oligonucleotide conjugates that were assembled in solution. Green-emitting QDs (gQDs) were FRET-paired with Cy3 acceptor. Hybridization of Cy3-labeled oligonucleotide targets provided the proximity required for FRET-sensitized emission from Cy3, which served as an analytical signal. The assay exhibited rapid transduction of nucleic acid hybridization within minutes. Without any amplification steps, the limit of detection of the assay was found to be 300 fmol with the upper limit of the dynamic range at 5 pmol. The implementation of glutathione-coated QDs for the development of nucleic acid hybridization assay integrated on a paper-based platform exhibited excellent resistance to nonspecific adsorption of oligonucleotides and showed no reduction in the performance of the assay in the presence of large quantities of noncomplementary DNA. The selectivity of nucleic acid hybridization was demonstrated by single-nucleotide polymorphism (SNP) detection at a contrast ratio of 19 to 1. The reuse of paper over multiple cycles of hybridization and dehybridization was possible, with less than 20% reduction in the performance of the assay in five cycles. This work provides an important framework for the development of paper-based solid-phase QD-FRET nucleic acid hybridization assays that make use of a ratiometric approach for detection and analysis. [ABSTRACT FROM AUTHOR]

In this technical note, we describe a facile method for one-step fabrication of paper-based microfluidic devices, by simply using commercially available permanent markers and metal templates with specific patterns. The fabrication process involves only a single step of plotting pattern in paper; it can be typically finished within 1 min. The ink marks formed in the patterned paper will act as the hydrophobic barriers to define the hydrophilic flow paths or separate test zones. Various paper devices can be created by using different templates with corresponding patterns. Transparent adhesive tape-sandwiched devices could protect their assay surfaces from potential contamination. In the proof-of-concept experiments, circular paper test zones (~3 mm diameter) were fabricated for colorimetric and quantification detection of prostate-specific antigen (PSA) as a model target, based on dot-immunogold staining assays coupled with gold enhancement amplification. Several serum specimens were additionally evaluated with this new approach and the results were compared with the commercial chemiluminescence immunoassay, validating its feasibility of practical applications. Such a one-step plotting method for paper patterning does not require any specialized equipments and skills, is quite inexpensive and rapid, and thus holds great potential to find wide applications especially in remote regions and resource-limited environments such as small laboratories and private clinics. [ABSTRACT FROM AUTHOR]

Paper spray is a newly developed ambient ionization method that has been applied for direct qualitative and quantitative analysis of biological samples. The properties of the paper substrate and spray solution have a significant impact on the release of chemical compounds from complex sample matrices, the diffusion of the analytes through the substrate, and the formation of ions for mass spectrometry analysis. In this study, a commercially available silica-coated paper was explored in an attempt to improve the analysis of therapeutic drugs in dried blood spots (DBS). The dichloromethane/isopropanol solvent has been identified as an optimal spray solvent for the analysis. The comparison was made with paper spray using chromatography paper as substrate with methanol/water as solvent for the analysis of verapamil, citalopram, amitriptyline, lidocaine, and sunitinib in dried blood spots. It has been demonstrated that the efficiency of recovery of the analytes was notably improved with the silica coated paper and the limit of quantitation (LOQ) for the drug analysis was 0.1 ng mL-1 using a commercial triple quadrupole mass spectrometer. The use of silica paper substrate also resulted in a sensitivity improvement of 5-50-fold in comparison with chromatography papers, including the Whatman ET31 paper used for blood cards. Analysis using a hand-held miniature mass spectrometer Mini 11 gave LOQs of 10-20 ng mL-1 for the tested drugs, which is sufficient to cover the therapeutic ranges of these drugs. [ABSTRACT FROM AUTHOR]

The improvements of adding sodium borohyride to the alkali sulfite–anthraquninone (AS–AQ) pulping process on properties of pulp and paper sheets was investigated. These properties were compared to those of the AS–AQ and the ethanol addition to AS–AQ (ASAE) pulping processes. The screened yield increased with alkali sulfite–antraquinone–sodium borohyride (ASAB) pulping process and kappa number decreased with respect to the AS–AQ process. Tensile and burst index of paper sheets improved with the ASAB pulping process, and the tear index for the ASAB pulping process was slightly decreased compared to that of the AS–AQ and ASAE pulping processes. It was determined that whiteness and brightness of papersheets decreased by adding sodium borohyride to the AS–AQ pulping process, whereas the opacity of papersheets did not change clearly compared to AS–AQ and ASAE pulping processes. [ABSTRACT FROM AUTHOR]

Poly(ethyleneimine) (PEI) microcapsules containing laccase from Trametes hirsuta(ThL) and Trametes versicolor(TvL) were printed onto paper substrate by three different methods: screen printing, rod coating, and flexo printing. Microcapsules were fabricated via interfacial polycondensation of PEI with the cross-linker sebacoyl chloride, incorporated into an ink, and printed or coated on the paper substrate. The same ink components were used for three printing methods, and it was found that laccase microcapsules were compatible with the ink. Enzymatic activity of microencapsulated TvL was maintained constant in polymer-based ink for at least eight weeks. Thick layers with high enzymatic activity were obtained when laccase-containing microcapsules were screen printed on paper substrate. Flexo printed bioactive paper showed very low activity, since by using this printing method the paper surface was not fully covered by enzyme microcapsules. Finally, screen printing provided a bioactive paper with high water-resistance and the highest enzyme lifetime. [ABSTRACT FROM AUTHOR]

Colloidal silver has gained wide acceptance as an antimicrobial agent, and various substrates coated with nanosilver such as fabrics, plastics, and metal have been shown to develop antimicrobial properties. Here, a simple method to develop coating of colloidal silver on paper using ultrasonic radiation is presented, and the coatings are characterized using X-ray diffraction (XRD), high resolution scanning electron microscope (HRSEM), and thermogravimetry (TGA) measurements. Depending on the variables such as precursor concentrations and ultrasonication time, uniform coatings ranging from 90 to 150 nm in thickness have been achieved. Focused ion beam (FIB) cross section imaging measurements revealed that silver nanoparticles penetrated the paper surface to a depth of more than 1 μm, resulting in highly stable coatings. The coated paper demonstrated antibacterial activity against E. coliand S. aureus, suggesting its potential application as a food packing material for longer shelf life. [ABSTRACT FROM AUTHOR]

The surface properties of paper depend not only on the fibrous matrix but also on the final treatment of the paper surface. The present work compares paper samples with two different surface sizing treatments by using AFM and profilometry to assess topography and roughness parameters as well as to evaluate the spreading of the sizing formulation and to estimate sizing agent particle sizes. The results were confronted with dynamic light scattering measurements regarding particle size. This work shows that AFM is a valuable technique to visualize and quantify the effects of sizing on the paper surface. Due to the small amount of surface sizing applied, no significant differences between the surface sized samples and the reference sample (without surface treatment) could be detected in terms of the surface roughness parameters. Nonetheless, those of sample B1 are systematically smaller than those of sample A1. [ABSTRACT FROM AUTHOR]

This technical note describes a detailed study on wax printing, a simple and inexpensive method for fabricating microfluidic devices in paper using a commercially available printer and hot plate. The printer prints patterns of solid wax on the surface of the paper, and the hot plate melts the wax so that it penetrates the full thickness of the paper. This process creates complete hydrophobic barriers in paper that define hydrophilic channels, fluid reservoirs, and reaction zones. The design of each device was based on a simple equation that accounts for the spreading of molten wax in paper. [ABSTRACT FROM AUTHOR]

A new approach to the measurement of x−yuniformity of the surface of a paper sheet is described. Scanning electron micrographs are taken of both the top and bottom surfaces of a paper sheet and image-analyzed. The images were converted to grayscale, and the standard deviation of the pixel brightness was called the “SEM roughness index” and calculated for each surface. Both commercial newsprint sheets and handsheets made with kraft, TMP, and recycled fibers were examined. Debonders and cationic polymers were added to some sheets. The addition of debonders increases the index on the top side of the sheet but decreases it on the bottom. This is caused by the movement of fines from the top to the bottom side. The addition of cationic polymers increases the SEM roughness index by increasing the degree of microfloc formation. Samples taken across a reel from a commercial paper machine tend to show a mirror image relationship between the top and bottom surfaces. The SEM roughness index is able to detect subtle changes in sheet structure caused by differences in the mode of addition of polymers used for retaining fines in the sheet. [ABSTRACT FROM AUTHOR]

The main purposes of filler addition in papermaking are to improve paper properties and reduce cost. The cost reduction is attributed to the low cost of the filler itself and to the energy savings that occur during the papermaking process. In this work, the effects of clay filler addition on the energy savings during the papermaking process, including water drainage, pressing, and drying, were systematically investigated. Experimental results indicated that the addition of filler could dramatically increase the drainage rate and the water removal rates during pressing and drying. With 20% filler addition, the drainage time decreased by 20% compared to the unfilled paper. At a filler content of 23%, the solids content of the handsheets after pressing increased at least 5 absolute points, and the drying rates increased by 20%. All these improvements can offer considerable benefits for paper mills, including enhanced machine speeds and large energy savings. [ABSTRACT FROM AUTHOR]

This paper presents an inkjet printing method for the fabrication of entire microfluidic multianalyte chemical sensing devices made from paper suitable for quantitative analysis, requiring only a single printing apparatus. An inkjet printing device is used for the fabrication of three-dimensional hydrophilic microfluidic patterns (550-μm-wide flow channels) and sensing areas (1.5 mm × 1.5 mm squares) on filter paper, by inkjet etching, and thereby locally dissolving a hydrophobic poly(styrene) layer obtained by soaking of the filter paper in a 1 wt % solution of poly(styrene) in toluene. In a second step, the same inkjet printing device is used to print "chemical sensing inks", comprising the necessary reagents for colorimetric analytical assays, into well-defined areas of the patterned microfluidic paper devices. The arrangement of the patterns, printed inks, and sensing areas was optimized to obtain homogeneous color responses. The results are "all-inkjet-printed" chemical sensing devices for the simultaneous determination of pH, total protein, and glucose in clinically relevant concentration ranges for urine analysis (0.46-46 μM for human serum albumin, 2.8-28.0 mM for glucose, and pH 5-9). Quantitative data are obtained by digital color analysis in the L*a*b* color space by means of a color scanner and a simple computer program. [ABSTRACT FROM AUTHOR]

The synthesis of deoxycholic acid (DCA)- and cholic acid (CA)-derived mixed tetraoxanes revealed that N-(2-dimethylamino)ethyl derivatives are potent antimalarials in vitro and in vivo. The tetraoxanes presented in this paper are dual inhibitors:  besides curing mice in vivo without observed toxic effects, they kill cancer cell lines at very low concentrations. For example, DCA and CA derivatives 16and 25cured 3/5 (160 mg/kg/day) and 2/5 (40 mg/kg/day, MTD >960 mg/kg), respectively, and they were extremely active against melanoma LOX IMVI cancer, LC5022 nM and 69 nM, respectively. [ABSTRACT FROM AUTHOR]

In this paper we demonstrate 3D two-photon recording and two-photon readout in photochromic polymer composites containing a mixture of 1,2-bis(2-methylbenzobthiophen-3-yl)hexafluorocyclopentene (diarylethene 1) and fluorene derivatives 2,2‘-(9,9-didecyl-9H-fluorene-2,7-diyl)bis(ethene-2,1-diyl)bis(4,1-phenylene)) dibenzodthiazole (2) or poly(9,9-didecyl-2,7-dipheylaminofluorene) (3). The recording mechanism in this system is based on two-photon excitation of the closed form of diarylethene 1at 800 nm. The readout mechanism is based on the modulation of the emission intensity of fluorene derivatives 2or 3by the closed form of diarylethene 1through Resonance Energy Transfer (RET). Föster distances (R0) and critical concentrations (A0) were calculated from the spectral overlap of the donor's emission (fluorene derivatives) and the acceptor's absorption (closed form of diarylethene 1) in solution and in polymer films of PMMA-co-VBP. This system was demonstrated to be suitable for recording data by two-photon excitation in thick storage media. The RET-based readout method proved to be essentially nondestructive (exhibiting a loss of the initial fluorescence emission less than 20% of the initial emission after 10 000 readout cycles), providing a solution to a long-standing challenge in photochromic optical data storage. [ABSTRACT FROM AUTHOR]

To increase the filler content in paper without sacrificing paper properties, clay−starch composites, made from a simple precipitation method, were used in papermaking. Compared to untreated clay, the clay−starch composite filled paper improved paper tensile strength up to 100−200%. Contrary to untreated clays that usually reduce the ZDT (z-directional tensile strength) of papers, the clay−starch composite actually increases the ZDT. The significant improvements in the paper strengths are attributed to the formation of a fiber−starch−filler sandwich structure, which avoids direct contact between filler and fiber. The specific shear bond strengths (expressed as specific bond strengths) between fillers and fibers were measured and used as the main variables for the modeling. It was also found that the fiber−fiber specific strength is weaker than the fiber−starch specific bond strength. The tensile strength (expressed as breaking length) was modeled by using a modified Page equation. The experimental results agreed very well with the modeling results. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes were examined as an adsorptive material for a thermally desorbed preconcentrator for organic vapors. The nanotubes were processed into a paper form and packed into a metal tube for flow- through sampling. Adsorbed vapors were released by a temperature-programmed desorption method and detected downstream with a flexural plate wave vapor sensor. The tested vapors, methyl ethyl ketone, toluene, and dimethyl methylphosphonate, were released from the packed column at different temperatures. The vapors were retained more strongly than previously observed for the widely used Tenax porous polymer, indicating a significant affinity of the single walled nanotubes for organic vapors. [ABSTRACT FROM AUTHOR]

This paper describes an efficient kinetic resolution process of trisubstituted cyclic olefins via a chiral dioxirane generated in situ from a fructose-derived ketone and Oxone. The substrates presented include a variety of 1,3-disubstituted and 1,6-disubstituted cyclohexenes with the stereogenic centers at allylic positions. A sequential desymmetrization and kinetic resolution of 1,4-cyciohexadienes by the chiral dioxirane was also found to be feasible. The initially formed monoepoxides can be kinetically resolved by continuing the reaction, leading to the increase or decrease of the ee values of monoepoxides depending on the diene systems. In some cases, a prochiral directing group is not required and the first formed epoxide stereoselectively directs the second epoxidation. When the coupled desymmetrization and kinetic resolution is used synergistically, high enantiopurity can be obtained for an epoxide from an intrinsically less enantioselective substrate. The observed absolute and relative stereochemistry as well as the changing optical purity can be effectively rationalized by transition state analysis. [ABSTRACT FROM AUTHOR]

Presents a study which demonstrates a pilot application of impulse dewatering of a primary paper mill sludge, conveyed by a metal belt through a heated nip. Information on the development of impluse drying; Where the primary sludge was obtained; How the peak nip pressure in the pilot impulse dryer was determined; Results of the study.

Looks at the importance of the preservation of paper. Description of the chemical reactions of the aging of paper; Use of mass deacidification methods; Evaluation of the mass deacidification processes; Evaluation of seven mass deacidification methods; Recent developments; Conclusions.

The article focuses on an experiment for the analysis of microbial activity in topsoil. It is stated that topsoil is the topmost layer of soil, which contains large amounts of bacteria and other microorganisms, that make the soil rich in nutrients to be used by plants. The microorganisms include bacteria, viruses, fungi, algae, and protozoa. In the experiment, qualitative analysis of microbial activities in topsoil is done by using white copy paper and a handmade cadmium sulfide-light emitting diode (CdS-LED) reflection photometer. White paper sheets are dipped in a soil solution, and treated with iodine, which results in a blue color. The depth of the blue color is measured by using the handmade reflection photometer.

Examines the chemistry involved in carbonless copy paper. Illustration of the basis of carbonless paper; Details on experiments conducted on carbonless paper; Method used in the examination of the paper; Information on the principles of carbonless paper.

The author reflects on visual color sensing, which is a form of analytical chemistry that involves titration indicators and pH paper. He states that the DNA hybridization-based specificity of this scheme attracts wide interest and a continuous stream of valuable research. He discusses that since 1996, there have been some innovations in the chemistry of making gold nanoparticles that brings out spectral and color changes.

The article focuses on a suitable substitute for weighing paper used by students in chemical laboratories. It reports that a suitable substitute may be found in patty paper sheets, the slips of paper used to separate hamburger patties. The use of these sheets can cut the cost of weighing paper by about seventy-five percent. Students can obtain patty paper through their school's dining services. Furthermore, the article provides some useful website addresses for students where the can obtain patty papers.

Reports on O.U. Heise and co-workers' investigation of industrial-scale, enzymatic de-inking. Pulp strength; Effluent oxygen demand.