bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of Coloured Impurities from Caprolactam Solution by Adsorption onto Activated Carbon: Equilibrium and Thermodynamic Studies
Authors: Zhang Hongtao , Luo YunBai , Yu Ping , Yuan Zhen
Published: August 2006

A large number of impurities appear during the production of caprolactam. Such impurities — especially coloured impurities — having a maximum UV absorbance at a wavelength of 290 nm, make it quite difficult to isolate the high-purity product. In order to improve the purification technology, the removal of the coloured impurities from caprolactam solution by adsorption onto activated carbon was studied with good results. The thermodynamic and mass-transfer behaviours of the adsorption process were also examined in this study with the values of Di, kid, Ea and E# being calculated. The magnitudes of the thermodynamic parameters ΔG0, ΔH0 and ΔS0 were also evaluated. A negative ΔG0 value confirmed the feasibility of the method and the spontaneous nature of the adsorption process. The positive value of ΔH0 indicated the endothermic nature of the process while the positive value of ΔS0 indicated an increase in the degrees of freedom of the adsorbed species. The value of ΔHiso increased with the extent of adsorption and showed a linear relationship when plotted against ln q.
Multi-Mode Shunt Damping of Piezoelectric Smart Panel for Noise Reduction
Authors: Kim Jaehwan
Published: August 2006

A piezoelectric smart panel is a plate structure on which a piezoelectric patch is attached with an electrical shunt circuit. When a sound is impinged on the panel structure, the structure vibrates and the attached piezoelectric patch produces an electrical energy, which can be effectively absorbed by the electrical shunt circuit. Since the energy absorption strongly depends on the vibration mode of the panel structure, many patches are required for broadband noise reduction. Thus, we report a multi-mode shunt damping of a smart panel by using a single piezoelectric patch in conjunction with a blocked shunt circuit. Modeling, shunt parameter tuning and implementation of the blocked shunt circuit along with an acoustic test of the panel are explained. A remarkable reduction of the transmitted noise was achieved for multiple modes of the panel. Since this technology has merits in terms of compactness, low cost, robustness and easiness to install, practical applications in many noise problems can be anticipated.
Calorimetric Determination of the Enthalpies of Formation of Hydrotalcite-Like Solids and Their Use in the Geochemical Modeling of Metals in Natural Waters
Authors: Allada Rama kumar , Peltier Edward , Navrotsky Alexandra , Casey William H. , Johnson C. Annette , Berbeco Hillary Thompson , Sparks Donald L.
Published: August 2006

Interest in hydrotalcite-like compounds has grown due to their role in controlling the mobility of aqueous metals in the environment as well as their use as catalysts, catalyst precursors and specialty chemicals. Although these materials have been studied in a number of contexts, little is known of their thermodynamic properties. High-temperature oxide melt solution calorimetry was used to measure the standard enthalpy of formation for compounds M(II)1−xAlx(OH)2(CO3)x/2·mH2O (0.2 < x < 0.4, M(II) = Mg, Co, Ni and Zn). The enthalpy of formation of these compounds from the relevant single cation phases was also determined. The formation of HTLCs results in a 5–20 kJ/mol enthalpy stabilization from the single cation hydroxides and carbonates and water. The data are correlated to two variables: the ratio of divalent to trivalent cation in the solid (M(II)/Al) and the identity of the divalent cation. It was observed that the M(II)/Al ratio exerts a minor influence on the enthalpy of formation from single-cation phases, while greater differences in stabilization resulted from changes in the chemical nature of the divalent cation. However, the data do not support any statistically significant correlation between the composition of HTLCs and their heats of formation. Equilibrium geochemical calculations based upon the thermodynamic data illustrate the effect of HTLCs on the speciation of metals in natural waters. These calculations show that, in many cases, HTLCs form even in waters that are undersaturated with respect to the individual divalent metal hydroxides and carbonates. Phase diagrams and stability diagrams involving Ni-bearing HTLCs and the single-cation components are presented. The Ni(II) concentration as a function of pH as well as the stability diagram for the equilibrium among minerals in the CaO-NiO-Al2O3-SiO2-CO2-H2O system at 298 K are plotted.
Controlled Polymerization of Metanilic Anion within the Interlayer of NiAl Layered Double Hydroxide
Authors: Tian Xiaofei , Wei Min , Evans David G. , Rao Guoying , Yang Heli
Published: August 2006

The controlled chemical oxidative polymerization of metanilic anion <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:c="http://cambridge.org/core/content" xmlns:core="http://cambridge.org/core" xmlns:m="http://cambridge.org/core/metadata" xmlns:cup="http://contentservices.cambridge.org" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest">(m-NH2C6H4SO3−)$(m{\rm{ - N}}{{\rm{H}}_2}{{\rm{C}}_6}{{\rm{H}}_4}{\rm{SO}}_3^ - )$ within the interlayer of NiAl layered double hydroxide was performed using, for the first time, ammonium persulfate as the oxidizing agent. The quantity of oxidizing agent required for control of the interlayer polymerization was investigated systematically and it was found that interleaved polyaniline sulfonic (PANIS) was present in different oxidation states and protonation levels when different quantities of external oxidizing agents were added. A mechanism for the oxidative polymerization of metanilic anion in NiAl layered double hydroxide is proposed, based on the intercalation of the oxidizing agent and the interlayer polymerization of monomer. The resulting PANIS/NiAl LDH composites were characterized by powder X-ray diffraction, ultraviolet-visible absorption spectra, Fourier transform infrared and X-ray photoelectron spectroscopy.
Sorption of Nitroaromatics by Ammonium- and Organic Ammonium-Exchanged Smectite: Shifts from Adsorption/Complexation to a Partition-Dominated Process
Authors: Roberts Michael G. , Li Hui , Teppen Brian J. , Boyd Stephen A.
Published: August 2006

Nitroaromatic compounds (NACs) are components of munitions commonly found as soil contaminants at military training sites and elsewhere. These compounds pose possible threats to human health and ecological systems. Recent studies indicate that these compounds are strongly retained by smectite clays. The adsorption mechanisms are not fully reconciled, but it is known that the type of exchangeable cation strongly affects NAC affinity for smectites. This study examined the sorption of 1,3-dinitrobenzene, 2,4-dinitrotoluene and naphthalene from water by a smectite clay (SWy-2) saturated with ammonium, tetramethylammonium (TMA), trimethylphenylammonium (TMPA) and hexadecyltrimethylammonium (HDTMA). In all cases, we observed greater sorption of 2,4-dinitrotoluene compared with 1,3-dinitrobenzene. The sorption isotherms for 2,4-dinitrotoluene and 1,3-dinitrobenzene displayed a concave-downward curve for NH4-SWy-2 and TMA-SWy-2, whereas the isotherms for sorption of HDTMA-SWy-2 and TMPA-SWy-2 were essentially linear. The magnitude of sorption followed the order: NH4-SWy-2 > TMA-SWy-2 > TMPA-SWy-2 > HDTMA-SWy-2 for both compounds. The greater affinity of NACs for NH4- and TMA-SWy-2 is due in part to complex formation between the exchangeable cation and −NO2 groups. These clays also provide near optimal interlayer distances that approximate the molecular thickness of NACs hence promoting the simultaneous interaction of the planar aromatic rings with opposing siloxane surfaces and solute dehydration. Both processes are energetically favorable. In HDTMA-SWy-2, sorption of all solutes is via a partition-dominated process. Solute competition (diminished uptake of one solute in the presence of a second) was observed for TMA-SWy-2 but not HDTMA-SWy-2. This is consistent with an adsorptive mechanism for TMA-SWy-2 and a partitioning mechanism for HDTMA-SWy-2. This study demonstrates that the dominant molecular mechanism of NAC sorption by smectite changes fundamentally from complexation between −NO2 groups and the exchangeable cation (viz. NH4 and TMA) to partitioning for a systematic series of ammonium and quaternary ammonium cations in which the locus of positive charge (the central N atom) is progressively shielded by organic moieties of increasing size.
Studies on the Adsorption of Dyes to Kaolinite
Authors: Harris Rodney G. , Johnson Bruce B. , Wells John D.
Published: August 2006

The strong adsorption to kaolinite of four polyaromatic, cationic dyes (9-aminoacridine, 3,6-diaminoacridine, azure A and safranin O), which adsorb much less to alumina or silica, was investigated by means of acid-base titrations, measurements of adsorption at varying pH and dye concentration, and by ATR-FTIR spectroscopy. The four dyes adsorb to kaolinite to similar extents, with little change over the pH range 3–10, but at higher pH (above the pKas of the dyes) the adsorption of 9-aminoacridine and 3,6-diaminoacridine decreases, that of azure A increases, and that of safranin O stays approximately constant. Although the dyes adsorb to kaolinite much more strongly than metal ions do, titration and spectroscopic data show that there is only limited chemical interaction between the adsorbed dyes and the kaolinite surface. The results indicate that electrostatic interaction between the dye molecules and the kaolinite surface is necessary for adsorption, but that hydrophobic interactions also contribute. It is proposed that the relatively hydrophobic silica faces of kaolinite, which carry low-density permanent negative charge, facilitate aggregation and adsorption of the positively charged, flat, aromatic dye molecules.
Competitive Adsorption of Cd and Dyes to Kaolinite
Authors: Harris Rodney G. , Johnson Bruce B. , Wells John D.
Published: August 2006

The competitive adsorption to kaolinite between Cd(II) and four polyaromatic dyes (9-aminoacridine, 3,6-diaminoacridine, azure A and safranin O) was studied in 5 mM KNO3 at 25°C. Under these conditions, Cd adsorbs to the silica face of kaolinite between about pH 4 and 6.5, but at higher pH, adsorbed Cd is progressively relocated to the crystal edges. In the presence of dye, less Cd adsorbed to kaolinite below pH 7. If sufficient dye was added to saturate the kaolinite surface, Cd adsorption was totally suppressed up to ∼pH 6. At higher pH, Cd followed the characteristic pattern for edge adsorption. In separate experiments 9-aminoacridine and azure A displaced pre-adsorbed Cd from kaolinite. The displacement curves were initially linear, with one Cd ion being displaced for every 13 dye molecules adsorbed at pH 5.5, and one Cd ion for every 35 dye molecules at pH 7.5. The interpretation of these results is that the dyes bind to kaolinite much more strongly than Cd(II) does, but only to the silica face.
Modeling the Adsorption of Organic Dye Molecules to Kaolinite
Authors: Harris Rodney G. , Wells John D. , Angove Michael J. , Johnson Bruce B.
Published: August 2006

Simple extended constant capacitance surface complexation models have been developed to represent the adsorption of polyaromatic dyes (9-aminoacridine, 3,6-diaminoacridine, azure A and safranin O) to kaolinite, and the competitive adsorption of the dyes with Cd. The formulation of the models was based on data from recent publications, including quantitative adsorption measurements over a range of conditions (varying pH and concentration), acid-base titrations and attenuated total reflectance-Fourier transform infrared spectroscopic data. In the models the dye molecules adsorb as aggregates of three or four, forming outer-sphere complexes with sites on the silica face of kaolinite. Both electrostatic and hydrophobic interactions are implicated in the adsorption processes. Despite their simplicity, the models fit a wide range of experimental data, thereby supporting the underlying hypothesis that the flat, hydrophobic, but slightly charged silica faces of kaolinite facilitate the aggregation and adsorption of the flat, aromatic, cationic dye molecules.
Redox Properties of Structural Fe in Ferruginous Smectite. A Discussion of the Standard Potential and its Environmental Implications
Authors: Favre Fabienne , Stucki Joseph W. , Boivin Pascal
Published: August 2006

The aim of this study was to compare the redox properties of oxides and smectite structural Fe (FeStr). Structural Fe in smectite often accounts for about half of the Fe pool in soils and sediments, and is naturally reduced by indigenous bacteria. This reaction is, however, seldom taken into account in environmental studies. The equation for the oxidation-reduction of FeStrand its application to the calculation of the standard electrode potential of FeStr,E0, are discussed on the basis of literature review. The resulting redox properties were used in a new analysis of previously reported field monitoring data. This agreed well with experimental observations that remained unexplained, and showed that if equilibrium conditions prevail, the FeStrpool in soils will reduce prior to the Fe in oxides. The FeStrpool is, therefore, likely to play a major role in controlling the bio-geochemistry of temporarily water-logged soils, and this reaction should be taken into account in further studies.
Differences in the Dehydration-Rehydration Behavior of Halloysites: New Evidence and Interpretations
Authors: Joussein Emmanuel , Petit Sabine , Fialips Claire-Isabelle , Vieillard Philippe , Righi Dominique
Published: August 2006

Two reference halloysites from New Zealand (Te Puke and Opotiki) were studied by X-ray diffraction under (1) various levels of relative humidity (RH) from 95 to 0% (dehydration), and (2) various temperatures increasing from 25 to 120°C (dehydration). They were also studied by differential thermal and thermogravimetric analyses at 40 and 0.2% RH. The impact of freeze drying along with the influence of cation saturation (Ca and K) on halloysite hydration were studied. The dehydration of the two halloysite samples upon decrease in RH started below 70% RH. However, the dehydration of Opotiki was still incomplete at ∼0% RH regardless of the saturation cation whereas Te Puke was completely dehydrated at ∼10% RH. For each sample, the decrease in RH and the increase in temperature induce similar dehydration behavior, but the dehydration processes of the Opotiki and Te Puke samples are different. The dehydration of Te Puke proceeds with one intermediate hydration state reacting as a separate phase due to the presence of ‘hole’ water molecules. The dehydration of the fully hydrated Opotiki halloysite gives a dehydrated phase and no 8.6 Å phase. The results suggest the presence of different types of water molecule, the ‘associated’ and the ‘hole’ water, controlling the dehydration behavior of halloysites. Freeze-dried halloysite samples are essentially dehydrated and the size of their coherent scattering domains is strongly reduced. Rehydration experiments performed after dehydration either at 95% RH or by immersing the sample in water for 3 months result in their partial rehydration. Calcium saturation promotes the rehydration process. The results suggest the presence of interlayer cations in the Opotiki sample, Ca ions being associated with the strongly held ‘hole’ water. As a result of this study, we assert that the (de)hydration behavior of halloysite is highly heterogeneous and cannot be generalized a priori.
Preparation of Porous Carbons from Halloysite-Sucrose Mixtures
Authors: Wang Ai-ping , Kang Feiyu , Huang Zheng-Hong , Guo Zhancheng
Published: August 2006

Porous carbons rich in mesopores and with large pore volumes have been prepared by polymerization and carbonization of a carbon precursor, sucrose, within a matrix of the natural clay, halloysite. The carbon precursor was impregnated into the pores of halloysite and mostly deposited on the external surface of the halloysite rods during impregnation. The inorganic matrix was removed by washing the carbon-mineral composite with HF and HCl. The resultant carbons were characterized by nitrogen adsorption analysis and were found to possess a large specific surface area, a large total pore volume and significant mesoporosity, without an activation process being involved. The pore volume and mesoporosity were up to 1.86 cm3/g and 78%, respectively, even at low carbonization temperatures (500°C). The size of the mesopores of the resultant carbons is mainly between 3 and 30 nm and the dominant pore size is ∼3.7 nm. The carbonization temperature has significant effects on the pore-size distribution and structure of the resultant carbons and carbon-mineral composites, respectively. This process is relatively simple and expected to cost less than the high-temperature carbonization process in the preparation of mesoporous carbons with total pore volume and large specific surface areas.
Structural and Chemical Alteration of Glauconite under Progressive Acid Treatment
Authors: Hassan Mervat S. , Baioumy Hassan M.
Published: August 2006

Boiling glauconite from the El-Gideda area of Egypt in different concentrations of HCl and H2SO4 for different periods led to a modified structure. Treatment resulted in progressive destruction of the structure, leaving X-ray amorphous silica and only relics of the original mineral. The glauconitic material was modified structurally in order to increase its adsorption activity. The glauconite was evaluated in terms of mineralogy, chemistry, morphology, structural modification, octahedral cation leaching rate, surface area and cation exchange capacity using X-ray diffraction, infrared spectroscopy, X-ray fluorescence, scanning electron microscopy and surface area analysis. The ratio of extracted octahedral cations to the total octahedral cations in the untreated glauconite was taken as a measure of octahedral sheet decomposition. A progressive decrease in crystallinity and the formation of X-ray amorphous silica Si-O vibration bands at 1100, 800 and 494 cm−1 accompanied octahedral cation depletion. Acid activation using 2 M and 4 M HCl for 6 h destroyed 30% and 61% of the octahedral sheet, respectively. In contrast, similar treatment using 2.9 and 5.5 M H2SO4 destroyed 48% and 93% of the octahedral sheet, respectively. Depending on the extent of cation depletion, the 4 M HCl product surface areas were as high as 259 m2/g, whereas the surface area of the 5.5 M H2SO4 product was only 63 m2/g. The progressive increase in surface area was due to glauconite morphology alteration. Acid-induced dissolution of Al, Fe, Mg cations from octahedral sheet edges led to a wedge-like splitting of the glauconite crystals, mesopore creation, and greater access to interlayer galleries.
Influence of Mechanical Compaction and Clay Mineral Diagenesis on the Microfabric and Pore-Scale Properties of Deep-Water Gulf of Mexico Mudstones
Authors: Aplin Andrew C. , Matenaar Ingo F. , McCarty Douglas K. , van der Pluijm Ben A.
Published: August 2006

We report on how the effects of mechanical compaction and clay mineral diagenesis have affected the alignment of phyllosilicates in a suite of Miocene-Pliocene mudstones buried to sub-seabed depths of between 1.8 and 5.8 km in the deep-water Gulf of Mexico. Mechanical compaction has reduced the porosity of the samples to 15% at 5 km, with modal pore sizes between 10 and 20 nm. High-resolution X-ray texture goniometry data show that the intense mechanical compaction has not resulted in a strongly aligned phyllosilicate fabric. The muds were apparently deposited with a weak or isotropic phyllosilicate fabric which was not substantially realigned by mechanical compaction. Unusually, X-ray diffraction of <0.2 µm separates shows that: (1) there is no illitization trend between 90 and 120°C; and (2) discrete smectite persists to ∼120°C, coexisting with R1 I-S or R0 I-S with 30–40% expandable layers. Between 120 and 130°C, discrete smectite disappears and the expandability of I-S decreases to ∼25–30%. We propose a two-stage diagenetic process involving (1) the alteration of volcanic glass to smectite and (2) the illitization of smectite and I-S; the alteration of glass results in smectite without a preferred orientation and retards the illitization reaction. We suggest that the lack of a strongly aligned phyllosilicate fabric reflects the apparently limited extent of illitization, and thus recrystallization, to which these mudstones have been subjected.
Pore-Scale Analysis of Bulk Volume Change from Crystalline Interlayer Swelling in Na+- and Ca2+-Smectite
Authors: Likos William J. , Lu Ning
Published: August 2006

Water-vapor sorption experiments were conducted to quantify bulk volume change of compacted expansive clay specimens resulting from interlayer hydration and dehydration in the crystalline swelling regime. Effects of interlayer cation type and pore fabric are examined by comparing results for natural Na+-smectite and Ca2+-smectite specimens compacted over a range of initial bulk densities. Transitions in interlayer hydration states are reflected in the general shape of the sorption isotherms and corresponding relationships between humidity and volume change. Hysteresis is observed in both the sorption and volume-change response. Volume change for Ca2+-smectite specimens is significantly greater than for Na+-smectite over the entire range of packing densities considered. Loosely compacted specimens result in less volume change for both clays. Results are interpreted in light of a conceptual framework based on previous SEM and TEM observations of particle and pore fabric for Na+ and Ca2+ smectite at high suctions. A pore-scale microstructural model is developed to quantitatively assess changes in interlayer and interparticle void volume during hydration. Modeling suggests that the relatively small volume changes observed for Na+-smectite are attributable to a reduction of interparticle void volume as expanding quasicrystals encroach into surrounding larger-scale pores. Volume change hysteresis is attributed to unrecovered alterations in interparticle fabric required to accommodate the swelling process. The results provide new insight to address volume change upscaling, hysteresis, and the general evolution of bi-modal pore fabric during crystalline swelling.
The Brass Light Pipe: An Easy Way to Obtain Infrared Spectra of Liquid Films and Monolayers
Authors: Larouche Pascal , Max Jean-Joseph , Chapados Camille
Published: August 2006

We describe a brass light pipe (LP) mounted in a cylindrical optical accessory for attenuated total reflection (ATR) that can be used to readily obtain the infrared spectra of liquids and monolayers. As examples, we show the LP spectra of isooctane, decane, dimethyl malonate, dodecanol, dodecanethiol, and acetic acid and compare them to those obtained by transmission as well as by ATR. In addition, we utilize a dodecanethiol monolayer spectrum to illustrate the sensitivity of the LP scheme.
New Method for Spectral Data Classification: Two-Way Moving Window Principal Component Analysis
Authors: Shinzawa Hideyuki , Morita Shigeaki , Ozaki Yukihiro , Tsenkova Roumiana
Published: August 2006

Two-way moving window principal component analysis (TMWPCA), which considers all possible variable regions by using variable and sample moving windows, is proposed as a new spectral data classification method. In TMWPCA, the similarity between model function and the index obtained by variable and sample moving windows is defined as “fitness”. For each variable region selected by a variable moving window, the fitness is obtained through the use of a model function. By maximizing the fitness, an optimal variable region can be searched. A remarkable advantage of TMWPCA is that it offers an optimal variable region for the classification. To demonstrate the potential of TMWPCA, it has been applied to the classification of visible–near-infrared (Vis-NIR) spectra of mastitic and healthy udder quarters of cows measured in a nondestructive manner. The misclassification rate of TMWPCA has been compared with those of other chemometric methods, such as principal component analysis (PCA), soft independent modeling of class analogies (SIMCA), and principal discriminant variate (PDV). TMWPCA has yielded the lowest misclassification rate. The result indicates that TMWPCA is a powerful tool for the classification of spectral data.
Orientation-Insensitive Spectra for Raman Microspectroscopy
Authors: Lefèvre Thierry , Rousseau Marie-Eve , Pézolet Michel
Published: August 2006

Separating effects due to molecular conformation from those due to orientation in the spectra of oriented samples obtained by Raman microspectroscopy is a complex issue. To solve this problem, we propose a procedure to calculate an orientation-insensitive spectrum (so-called isotropic spectrum) from polarized spectra obtained by Raman microspectroscopy that is valid for systems that exhibit a uniaxial symmetry. The method has first been tested on highly oriented samples of high-density polyethylene (HDPE). Polarized and isotropic spectra of a highly oriented HDPE cylindrical rod and an isotropic HDPE sample have been compared. The differences in the relative intensities, which occur in the polarized spectra and are due to orientation of the polyethylene chains, are nearly cancelled in the isotropic spectra, showing that the orientation-insensitive spectrum adequately represents the molecular conformation without contributions of orientation. Second, spectra of silk fibroins have been compared in the amide I region for Bombyx mori cocoon silk fibers and methanol-treated regenerated fibroin films. The similarity of the shape of the amide I band of the isotropic spectra indicates that the secondary structure of the fibroins is very close in both samples. These experimental results support the conclusion that the molecular conformation can be efficiently characterized from the intensity and the shape of Raman bands in the orientation-insensitive spectrum.
Chemical Imaging of Wood—Polypropylene Composites
Authors: Harper David P. , Wolcott Michael P.
Published: August 2006

Recent investigations of wood plastic composites have revealed a detrimental effect of using lubricant systems in production. This includes nullifying part or all of the mechanical benefit of using a polar compatibilizer, maleic anhydride polypropylene (MAPP), in the composite formulation. This investigation utilizes lubricants labeled with deuterium in conjunction with Fourier transform infrared (FT-IR) spectroscopy to allow for the separation of individual lubricants from all other material constituents. All of the deuterium labeled lubricants, used without MAPP, revealed their expulsion from the wood interface during crystallization. MAPP coupling agent was found to exist near the wood, but it is unclear if any covalent bonding with the hydroxyl functionality on the wood surface occurred. The addition of zinc stearate lubricants appears to nullify the activity of the anhydride functionality near the wood surface as evidenced by a shift in the FT-IR spectra to the hydrolyzed form of the coupling agent. Most of the additives collect at the edges of the spherulites in mostly amorphous regions of the material. The consequence of this morphology may be a weak interface between crystallites.
Infrared Transmission Spectrometry for the Determination of Urea in Microliter Sample Volumes of Blood Plasma Dialysates
Authors: Kondepati Venkata Radhakrishna , Damm Uwe , Heise H. Michael
Published: August 2006

Application of mid-infrared spectroscopy for the determination of urea in blood plasma dialysates of microliter sample volumes using a transmission microcell was investigated. Infrared spectra of the dialysates of plasma samples collected from 75 different patients using CMA 60 microdialysis catheters were evaluated with multivariate partial least squares regression. Using the absorbance spectral data from 1520–1420 cm−1 and 1220–1120 cm−1, a minimum standard error of prediction (SEP) of 0.88 mg/dL (0.14 mM) was achieved with spectral variable selection. Our findings suggest the feasibility of developing a mid-infrared sensor in combination with micro-fluidics for on-line monitoring of urea in patients undergoing dialysis treatment.
Wavelength Modulated Cavity Enhanced Absorption Spectroscopy of Water in the 1.37 μm Region
Authors: Vasudev R.
Published: August 2006

We describe the performance of a high-sensitivity wavelength modulated cavity enhanced infrared tunable diode laser absorption spectrometer for the detection of water vapor in the 1.37 μm region. The spectrometer can measure a fractional absorption of ∼10−5 for an absorption path length of a few kilometers. The instrument's sensitivity is more than sufficient to detect water isotopomers (H216O, H218O, HDO) at Martian atmospheric concentrations. The instrument is amenable to miniaturization, so a future compact, multiple-species version of the spectrometer will be highly suitable for in situ planetary exploration.
Aligned Silver Nanorod Arrays as Substrates for Surface-Enhanced Infrared Absorption Spectroscopy
Authors: Leverette C. L. , Jacobs S. A. , Shanmukh S. , Chaney S. B. , Dluhy R. A. , Zhao Y.-P.
Published: August 2006

Preferentially aligned silver nanorod arrays prepared by oblique angle vapor deposition were evaluated as substrates for surface-enhanced infrared absorption (SEIRA) spectroscopy. These nanorod arrays have an irregular surface lattice and are composed of tilted, cylindrically shaped nanorods that have an average length of 868 nm ± 95 nm and an average diameter of 99 nm ± 29 nm. The overall enhancement factor for chemisorbed organic films of para-nitrobenzoic acid (PNBA) deposited onto the Ag nanorod arrays analyzed by external reflection SEIRA was calculated to be 31 ± 9 compared to infrared reflection–absorption spectroscopy (IRRAS) obtained from a 500 nm Ag film substrate. This enhancement is attributed to the unique optical properties of the nanorod arrays as well as the increased surface area provided by the nanorod substrate. SEIRA reflection–absorbance intensity was observed with both p- and s-polarized incident radiation with angles of incidence ranging from 25° to 80°. The largest intensity was achieved with p-polarization and incident angles larger than 75°. Polarization-dependent ultraviolet/visible/near-infrared (UV/Vis/NIR) spectra of the nanorod arrays demonstrate that the red-shifted surface plasmon peaks of the elongated nanorods may be partially responsible for the observed SEIRA response. The SEIRA detection limit for the Ag nanorod arrays was estimated to be 0.08 ng/cm2. Surface-enhanced Raman scattering (SERS) and SEIRA analysis of chemisorbed PNBA utilizing the same nanorod substrate is demonstrated.
Fourier Transform Hyperspectral Visible Imaging and the Nondestructive Analysis of Potentially Fraudulent Documents
Authors: Brauns Eric B. , Dyer R. Brian
Published: August 2006

The work presented in this paper details the design and performance characteristics of a new hyperspectral visible imaging technique. Rather than using optical filters or a dispersing element, this design implements Fourier transform spectroscopy to achieve spectral discrimination. One potentially powerful application of this new technology is the nondestructive analysis and authentication of written and printed documents. Document samples were prepared using red, blue, and black inks. The samples were later altered using a different ink of the same color. While the alterations are undetectable to the naked eye, the alterations involving the blue and black inks were easily detected when the spectrally resolved images were viewed. Analysis of the sample using the red inks was unsuccessful. A 2004 series $20 bill was imaged to demonstrate the application to document authentication. The results argue that counterfeit detection and quality control during printing are plausible applications of Fourier transform hyperspectral visible imaging. All of the images were subjected to fuzzy c-means cluster analysis in an effort to objectively analyze and automate image analysis. Our results show that cluster analysis can distinguish image features that have remarkably similar visible transmission spectra.
Cavity Ring-down Spectroscopy for Detection in Liquid Chromatography: Extension to Tunable Sources and Ultraviolet Wavelengths
Authors: Van Der Sneppen L. , Wiskerke A. E. , Ariese F. , Gooijer C. , Ubachs W.
Published: August 2006

In earlier studies, it was demonstrated that the sensitivity of absorbance detection in liquid chromatography (LC) can be improved significantly by using cavity ring-down spectroscopy (CRDS). Thus far, CRDS experiments have been performed using visible laser light at fixed standard wavelengths, such as 532 nm. However, since by far most compounds of analytical interest absorb in the ultraviolet (UV), it is of utmost importance to develop UV-CRDS. In this study, as a first step towards the deep-UV region, LC separations with CRDS detection (using a previously described liquid-only cavity flow cell) at 457 and 355 nm are reported for standard mixtures of dyes and nitro-polyaromatic hydrocarbons (nitro-PAHs), respectively. For the measurements in the blue range a home-built optical parametric oscillator (OPO) system, tunable between 425 and 478 nm, was used, achieving a baseline noise of 2.7 × 10−6 A.U. at 457 nm, improving upon the sensitivity of conventional absorbance detection (typically around 10−4 A.U.). An enhancement of the sensitivity can be seen at 355 nm as well, but the improvement of the baseline noise (1.3 × 10−5 A.U.) is much less pronounced. The sensitivity at 355 nm is limited by the quality of the UV-CRDS mirrors that are currently available: whereas the ring-down times as obtained at 457 nm are around 70–80 ns for the eluent, they are only 20–25 ns at 355 nm. Critical laser characteristics for LC-CRDS measurements, such as pulse length and mode structure, are given and prospects for going to shorter wavelengths are discussed.
Remote Pulsed Raman Spectroscopy of Inorganic and Organic Materials to a Radial Distance of 100 Meters
Authors: Sharma S. K. , Misra A. K. , Lucey P. G. , Angel S. M. , McKay C. P.
Published: August 2006

A portable pulsed remote Raman spectroscopy system has been fabricated and tested to 100 m radial distance. The remote Raman system is based on a directly coupled f/2.2 spectrograph with a small (125 mm diameter) telescope and a frequency-doubled Nd:YAG pulsed laser (20 Hz, 532 nm, 25 mJ/pulse) used as the excitation source in a co-axial geometry. The performance of the Raman system is demonstrated by measuring the gated Raman spectra of calcite, sodium phosphate, acetone, and naphthalene. Raman spectra of these materials were recorded with the 532 nm pulsed laser excitation and accumulating the spectra with 600 laser shots (30 s integration time) at 100 m with good signal-to-background ratio. The remote pulsed Raman system can be used for remotely identifying both inorganic and organic materials during daytime or nighttime. The system will be useful for terrestrial applications such as monitoring environmental pollution and for detecting minerals and organic materials such as polycyclic aromatic hydrocarbons (PAHs) on planetary surfaces such as Mars.
Photoelectron Spectroscopy Characterization of Diamond-like Carbon Films
Authors: Mašek K. , Fabík S. , Mašková A. , Tsud N. , Veltruská K. , Prince K. C. , Cháb V. , Vyskočil J. , Matolín V.
Published: August 2006

The electronic states of diamond-like hydrogenated carbon (DLC) films were studied by synchrotron radiation photoelectron spectroscopy. The valence band spectra measured at different excitation energies show the gradual emergence of the p-π band in relation to the sample annealing and ion bombardment amorphization. The p-π band of the annealed DLC was characterized by localized pz states, while the formation of the amorphous carbon surface was accompanied by appearance of the delocalized pz states, which reduce the optical gap. A simple approach permitting the extraction of the 2 p band shape from the photoelectron spectra is proposed.
Remote Imaging Laser-Induced Breakdown Spectroscopy and Laser-Induced Fluorescence Spectroscopy Using Nanosecond Pulses from a Mobile Lidar System
Authors: Grönlund Rasmus , Lundqvist Mats , Svanberg Sune
Published: August 2006

A mobile lidar system was used in remote imaging laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) experiments. Also, computer-controlled remote ablation of a chosen area was demonstrated, relevant to cleaning of cultural heritage items. Nanosecond frequency-tripled Nd:YAG laser pulses at 355 nm were employed in experiments with a stand-off distance of 60 meters using pulse energies of up to 170 mJ. By coaxial transmission and common folding of the transmission and reception optical paths using a large computer-controlled mirror, full elemental imaging capability was achieved on composite targets. Different spectral identification algorithms were compared in producing thematic data based on plasma or fluorescence light.
Semi-Parametric Estimation in the Compositional Modeling of Multicomponent Systems from Raman Spectroscopic Data
Authors: Sowa Michael G. , Smith Michael S. D. , Kendall Catherine , Bock Erika R. , Ko Alex C.-T. , Choo-Smith Lin-P'ing , Stone Nicholas
Published: August 2006

Identification and quantification of molecular species are central applications of molecular spectroscopy. In complex multicomponent systems like tissue samples, linear parametric models are often used to estimate the relative concentrations of the biochemical components of the sample. In situations where not all of the components of the sample are known or modeled, such parametric models can suffer from omitted variable bias and result in skewed estimates of component concentrations. We propose a semi-parametric approach that tries to avoid this omitted variable bias by effectively including unknown covariates as a non-parametric term in the regression equation. Constituent concentrations estimated with such partial linear models should outperform strict parametric linear models when the user has limited information on the composition of a multi-constituent system.
Quantification of Volatile Organics in Soil Aging Experiments Using Fourier Transform Infrared Spectroscopy
Authors: Thompson Christopher J. , Riley Robert G. , Amonette James E. , Gassman Paul L.
Published: August 2006

On-line Fourier transform infrared (FT-IR) spectroscopy was applied to monitor the concentration of halogenated volatile organic compounds in a sample-preparation process that simulates long-term, slow accumulation of contaminants in soils (i.e., aging). Artificial aging is conducted by circulating a supercritical fluid solution containing the contaminant(s) of interest through a packed soil column. Mid-infrared spectra of several volatile halocarbons were measured in supercritical Xe and CO2 to evaluate possible interferences from the strong absorption of CO2. Although some of the C–X bands were partially masked in supercritical CO2, all of the compounds studied had distinct spectral features in the region 1400–700 cm−1 and could be monitored in either solvent. Quantitative measurements of halogenated volatile organics in supercritical CO2 were demonstrated with CCl4. Excellent results were obtained over the range 7–280 mM. Representative artificial aging experiments were conducted on two test soils using CCl4 as the contaminant. On-line (FT-IR) estimates of the aged soil concentrations were 1.3–4.4 times higher than off-line concentrations obtained by gas chromatography/mass spectrometry. The discrepancies were primarily ascribed to post-aging losses that occurred during depressurization and subsequent sample handling. FT-IR spectroscopy is shown to be a powerful tool for monitoring soil loading behavior and for developing artificial aging protocols.
Factors Determining the Stability, Resolution, and Precision of a Conventional Raman Spectrometer
Authors: Fukura Satoshi , Mizukami Tomoyuki , Odake Shoko , Kagi Hiroyuki
Published: August 2006

We verified the performance of a conventional Raman spectrometer, which is composed of a 30 cm single polychromator, a Si based charge-coupled device (CCD) camera, and a holographic supernotch filter. For that purpose, the time change of the peak positions of Raman spectra of naphthalene and fluorescence spectra of ruby (Cr-doped Al2O3) were monitored continually. A time-dependent deviation composed of two components was observed: a monotonous drift up to 0.4 cm−1 and a periodic oscillation with a range of 0.15 cm−1. The former component was stabilized at approximately 2000 s after the CCD detector was cooled, indicating that incomplete refrigeration of the CCD detector induced the drift. The latter component synchronized with the periodic oscillation of the room temperature, indicating that thermal expansion or contraction of the whole apparatus induced this oscillation. The implemental deviation is reduced when measurements are conducted using a sufficiently cooled CCD detector at a constant room temperature. Moreover, the effect of the room temperature oscillation is lowered in a spectrum acquired over a duration that is longer than one cycle of this oscillation. Applying the least squares fitting method to carefully measured spectra enhanced the precision of the determination of the peak position to 0.05 cm−1 using the spectrometer with pixel resolution of 1.5 cm−1.
Gold Nanoparticle-Based pH Sensor in Highly Alkaline Region at pH > 11: Surface-Enhanced Raman Scattering Study
Authors: Lim Jong Kuk , Joo Sang-Woo
Published: August 2006

A surface plasmon resonance spectroscopy study showed that citrate-reduced gold nanoparticles (∼15 nm diameter, ∼9 × 10−9 M concentration, ∼2 × 10−2 M ionic strength) were found to be utilized as a colorimetric sensor by exhibiting a distinct color change at a highly alkaline pH > 11.5. Surface-enhanced Raman scattering (SERS) of 4-ethynylpyridine (4-EP) on gold nanoparticle surfaces indicated that the multiple peaks in the v(C≡C) stretching bands should vary significantly in the highly alkaline region from pH 12 to 14. As the pH value increased, the v(C≡C) stretching band intensity at ∼2080 cm−1 became stronger than that at ∼2010 cm−1. The p K1/2 value was determined to be around 13 by the SERS titration of taking intensity ratios of I2080 with respect to I2010. Using SERS enhancements and conspicuous spectral changes, self-assembled monolayers (SAMs) of 4-EP on Au nanoparticles holds potential as a pH sensor for sensitive detection of the hydroxide OH− concentration at around pH 13 in an aqueous solution. The pH calibration from SERS titration of 4-EP is expected to have advantages in terms of higher alkaline detection limit and more precise measurements, if compared with the indigo carmine, the p K1/2 value of which is 12.2.
Development of Size-Selective Sampling of Bacillus Anthracis Surrogate Spores from Simulated Building Air Intake Mixtures for Analysis via Laser-Induced Breakdown Spectroscopy
Authors: Gibb-Snyder Emily , Gullett Brian , Ryan Shawn , Oudejans Lukas , Touati Abderrahmane
Published: August 2006

Size-selective sampling of Bacillus anthracis surrogate spores from realistic, common aerosol mixtures was developed for analysis by laser-induced breakdown spectroscopy (LIBS). A two-stage impactor was found to be the preferential sampling technique for LIBS analysis because it was able to concentrate the spores in the mixtures while decreasing the collection of potentially interfering aerosols. Three common spore/aerosol scenarios were evaluated, diesel truck exhaust (to simulate a truck running outside of a building air intake), urban outdoor aerosol (to simulate common building air), and finally a protein aerosol (to simulate either an agent mixture (ricin/anthrax) or a contaminated anthrax sample). Two statistical methods, linear correlation and principal component analysis, were assessed for differentiation of surrogate spore spectra from other common aerosols. Criteria for determining percentages of false positives and false negatives via correlation analysis were evaluated. A single laser shot analysis of approximately 4 percent of the spores in a mixture of 0.75 m3 urban outdoor air doped with approximately 1.1 × 105 spores resulted in a 0.04 proportion of false negatives. For that same sample volume of urban air without spores, the proportion of false positives was 0.08.
Spectral Range Optimization for the Near-Infrared Quantitative Analysis of Petrochemical and Petroleum Products: Naphtha and Gasoline
Authors: Lee Youngbok , Chung Hoeil , Kim Nakjoong
Published: August 2006

The proper selection of the spectral range in partial least squares (PLS) calibration is critical when highly overlapping spectra from compositionally complex samples are used, such as naphtha and gasoline. In particular, the relevant spectral information related to a given property is frequently localized in a narrow range, and the most selective region may be difficult to locate. We have presented the importance of range optimization in near-infrared (NIR) spectroscopy for the analyses of petrochemical and petroleum products that are generally highly complex in composition. For this purpose, the determination of a detailed compositional analysis (so called PIONA) and the distillation temperature of naphtha were evaluated. In the same fashion, the research octane number (RON) and Reid vapor pressure (RVP) were selected for gasoline. By optimizing the range using moving window (MW) PLS, the overall calibration performance was improved by finding the optimal spectral range for each property. In particular, for a detailed compositional analysis of naphtha, it was effective to search for localized spectral information in a relatively narrow range with fewer factors.
The Elastomer Gage for Local Strain Measurement in Monotonic and Cyclic Soil Testing
Authors: Safaqah OA , Riemer MF
Published: August 2006

This study introduces a new type of local strain gages for soil testing called the elastomer gage. It is the first on-sample local strain gage that is flexible enough to be attached to the inside of a conventional latex membrane so that the gage is in full contact with the soil's sample surface. The gage has very versatile design characteristics including variable length and sensitivity, which enable measurement over a wide range of static and cyclic strains. The gage can be used in many testing systems including triaxial, torsional shear, and simple shear devices to directly measure axial, circumferential, and shear strains. The gage has been validated in triaxial and torsional testing systems using a “calibration sample” made of urethane with known stiffness.
New Apparatus for Evaluating Filter Performance for Dams Containing Cracks
Authors: Brandon TL , Park Y , Duncan JM
Published: August 2006

A new test apparatus has been developed to evaluate filter performance when both the filter and the core _base_ material have been cracked. This apparatus allows the orientation of the crack to be horizontal or vertical, and accommodates flow in the horizontal and vertical directions as well. The applied hydraulic gradient and the thickness of the crack can also be varied.Two apparatuses have been constructed and tested. The smaller apparatus allows testing of truncated cylindrical test specimens that are 10 cm in diameter by 20 cm long. The larger apparatus allows testing of specimens that are approximately 30 by 30 by 30 cm. An automated data acquisition system was developed to measure the pressures and flow rates through the test specimens as well as obtaining a video record of the filter performance. In successful tests, the filter slumped to fill the crack, the flow rate decreased, and the head water pressure increased. In failed tests, the filter never slumped to fill the crack, the flow rate remained high, and the head water pressure stayed very low. The relative success of failure of a filter system could be assessed by the video record as well.