Modeling radiative and non-radiative pathways at both the Franck-Condon and Herzberg-Teller approximation level.

Here, we present a concise model that can predict the photoluminescent properties of a given compound from first principles, both within and beyond the Franck-Condon approximation. The formalism required to compute fluorescence, Internal Conversion (IC), and Inter-System Crossing (ISC) is discussed. The IC mechanism, in particular, is a difficult pathway to compute due to difficulties associated with the computation of required bosonic configurations and non-adiabatic coupling elements. Here, we offer a discussion and breakdown on how to model these pathways at the Density Functional Theory (DFT) level with respect to its computational implementation, strengths, and current limitations. The model is then used to compute the photoluminescent quantum yield (PLQY) of a number of small but important compounds: anthracene, tetracene, pentacene, diketo-pyrrolo-pyrrole (DPP), and Perylene Diimide (PDI) within a polarizable continuum model. Rate constants for fluorescence, IC, and ISC compare well for the most part with respect to experiment, despite triplet energies being overestimated to a degree. The resulting PLQYs are promising with respect to the level of theory being DFT. While we obtained a positive result for PDI within the Franck-Condon limit, the other systems require a second order correction. Recomputing quantum yields with Herzberg-Teller terms yields PLQYs of 0.19, 0.08, 0.04, 0.70, and 0.99 for anthracene, tetracene, pentacene, DPP, and PDI, respectively. Based on these results, we are confident that the presented methodology is sound with respect to the level of quantum chemistry and presents an important stepping stone in the search for a tool to predict the properties of larger coupled systems.

Dispersion Aerosol Indirect Effect in Turbulent Clouds: Laboratory Measurements of Effective Radius.

Cloud optical properties are determined not only by the number density n d and mean radius r ¯ of cloud droplets but also by the shape of the droplet size distribution. The change in cloud optical depth with changing n d , due to the change in distribution shape, is known as the dispersion effect. Droplet relative dispersion is defined as d = σ r / r ¯ . For the first time, a commonly used effective radius parameterization is tested in a controlled laboratory environment by creating a turbulent cloud. Stochastic condensation growth suggests d independent of n d for a nonprecipitating cloud, hence nearly zero albedo susceptibility due to the dispersion effect. However, for size-dependent removal, such as in a laboratory cloud or highly clean atmospheric conditions, stochastic condensation produces a weak dispersion effect. The albedo susceptibility due to turbulence broadening has the same sign as the Twomey effect and augments it by order 10%.

Influence of Turbulent Fluctuations on Cloud Droplet Size Dispersion and Aerosol Indirect Effects.

Cloud droplet relative dispersion, defined as the standard deviation over the mean cloud droplet size, is of central importance in determining and understanding aerosol indirect effects. In recent work, it was found that cloud droplet size distributions become broader as a result of supersaturation variability and that the sensitivity of this effect is inversely related to cloud droplet number density. The subject is investigated in further detail using an extensive dataset from a laboratory cloud chamber capable of producing steady-state turbulence. An extended stochastic theory is found to successfully describe properties of the droplet size distribution, including an analytical expression for the relative dispersion. The latter is found to depend on the cloud droplet removal time, which in turn increases with the cloud droplet number density. The results show that relative dispersion decreases monotonically with increasing droplet number density, consistent with some recent atmospheric observations. Experiments spanning fast to slow microphysics regimes are reported. The observed dispersion is used to estimate time scales for autoconversion, demonstrating the important role of the turbulence-induced broadening effect on precipitation development. An initial effort is made to extend the stochastic theory to an atmospheric context with a steady updraft, for which autoconversion time is the controlling factor for droplet lifetime. As in the cloud chamber, relative dispersion is found to increase with decreasing cloud droplet number density.

Use of Fourier-transform infrared spectroscopy to quantify immunoglobulin G concentration and an analysis of the effect of signalment on levels in canine serum.

Deficiency in immunoglobulin G (IgG) is associated with an increased susceptibility to infections in humans and animals, and changes in IgG levels occur in many disease states. In companion animals, failure of transfer of passive immunity is uncommonly diagnosed but mortality rates in puppies are high and more than 30% of these deaths are secondary to septicemia. Currently, radial immunodiffusion (RID) and enzyme-linked immunosorbent assays are the most commonly used methods for quantitative measurement of IgG in dogs. In this study, a Fourier-transform infrared spectroscopy (FTIR) assay for canine serum IgG was developed and compared to the RID assay as the reference standard. Basic signalment data and health status of the dogs were also analyzed to determine if they correlated with serum IgG concentrations based on RID results. Serum samples were collected from 207 dogs during routine hematological evaluation, and IgG concentrations determined by RID. The FTIR assay was developed using partial least squares regression analysis and its performance evaluated using RID assay as the reference test. The concordance correlation coefficient was 0.91 for the calibration model data set and 0.85 for the prediction set. A Bland-Altman plot showed a mean difference of -89 mg/dL and no systematic bias. The modified mean coefficient of variation (CV) for RID was 6.67%, and for FTIR was 18.76%. The mean serum IgG concentration using RID was 1943 ± 880 mg/dL based on the 193 dogs with complete signalment and health data. When age class, gender, breed size and disease status were analyzed by multivariable ANOVA, dogs < 2 years of age (p = 0.0004) and those classified as diseased (p = 0.03) were found to have significantly lower IgG concentrations than older and healthy dogs, respectively.

Nucleation at the contact line observed on nanotextured surfaces.

It has been conjectured that roughness plays a role in surface nucleation, the tendency for freezing to begin preferentially at the liquid-gas interface. Using high speed imaging, we sought evidence for freezing at the contact line on catalyst substrates with imposed characteristic length scales (texture). Length scales consistent with the critical nucleus size and with δ∼τ/σ, where τ is a relevant line tension and σ is the surface tension, range from nanometers to micrometers. It is found that nanoscale texture causes a shift in the nucleation of ice in supercooled water to the three-phase contact line, while microscale texture does not.

Use of Fourier-transform infrared spectroscopy to quantify immunoglobulin G concentrations in alpaca serum.

BACKGROUND: Rapid, economical, and quantitative assays for measurement of camelid serum immunoglobulin G (IgG) are limited. In camelids, failure of transfer of maternal immunoglobulins has a reported prevalence of up to 20.5%. An accurate method for quantifying serum IgG concentrations is required. OBJECTIVE: To develop an infrared spectroscopy-based assay for measurement of alpaca serum IgG and compare its performance to the reference standard radial immunodiffusion (RID) assay. ANIMALS: One hundred and seventy-five privately owned, healthy alpacas. METHODS: Eighty-two serum samples were collected as convenience samples during routine herd visits whereas 93 samples were recruited from a separate study. Serum IgG concentrations were determined by RID assays and midinfrared spectra were collected for each sample. Fifty samples were set aside as the test set and the remaining 125 training samples were employed to build a calibration model using partial least squares (PLS) regression with Monte Carlo cross validation to determine the optimum number of PLS factors. The predictive performance of the calibration model was evaluated by the test set. RESULTS: Correlation coefficients for the IR-based assay were 0.93 and 0.87, respectively, for the entire data set and test set. Sensitivity in the diagnosis of failure of transfer of passive immunity (FTPI) ([IgG] <1,000 mg/dL) was 71.4% and specificity was 100% for the IR-based method (test set) as gauged relative to the RID reference method assay. CONCLUSIONS AND CLINICAL IMPORTANCE: This study indicated that infrared spectroscopy, in combination with chemometrics, is an effective method for measurement of IgG in alpaca serum.

Feasibility of infrared spectroscopy with pattern recognition techniques to identify a subpopulation of mares at risk of producing foals diagnosed with failure of transfer of passive immunity.

OBJECTIVE: To assess the feasibility of a serum-based test using infrared spectroscopy to identify a subpopulation of mares at risk of producing foals susceptible to failure of passive transfer of immunity (FPT) because of mare-associated factors. MATERIALS AND METHODS: Serum was collected from post-parturient mares (n = 126) and their foals at 24-72 h of age. A radial immunodiffusion IgG test was used to determine each foal's serum IgG concentration. Infrared absorbance spectra of dam sera were collected in the wave number range of 400-4000 cm(-1). Following data preprocessing, pattern recognition techniques were used to identify spectroscopic information capable of distinguishing between mares with FPT foals and those with normal foals. The sensitivity and specificity of infrared spectroscopy to detect risk-positive mares were calculated. RESULTS: Five wave number regions were identified as optimal for distinguishing between the two groups of mares: 740.9-785.2 cm(-1), 796.8-816.0 cm(-1), 970.4-993.5 cm(-1), 1371.6-1406.3 cm(-1) and 1632.0-1659.0 cm(-1). Based upon the infrared spectroscopic information within these discriminatory subregions, the spectra provided the risk status of the mares with a classification success rate of 81.0%. The sensitivity of the classification system was 85.7% and specificity was 80.0%. CONCLUSION: This preliminary study demonstrates that infrared spectra of dam serum have the potential to provide the basis for a new periparturient screening method for a subpopulation of mares at risk of having a foal susceptible to FPT. Further development may provide an economic and rapid technique for the pre-parturient assessment of mares.

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina.

Arsenic (As) speciation in surface and groundwater from two provinces in Argentina (San Juan and La Pampa) was investigated using solid phase extraction (SPE) cartridge methodology with comparison to total arsenic concentrations. A third province, Río Negro, was used as a control to the study. Strong cation exchange (SCX) and strong anion exchange (SAX) cartridges were utilised in series for the separation and preservation of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MA(V)) and dimethylarsinic acid (DMA(V)). Samples were collected from a range of water outlets (rivers/streams, wells, untreated domestic taps, well water treatment works) to assess the relationship between total arsenic and arsenic species, water type and water parameters (pH, conductivity and total dissolved solids, TDS). Analysis of the waters for arsenic (total and species) was performed by inductively coupled plasma mass spectrometry (ICP-MS) in collision cell mode. Total arsenic concentrations in the surface and groundwater from Encon and the San José de Jáchal region of San Juan (north-west Argentina within the Cuyo region) ranged from 9 to 357 µg l(-1) As. Groundwater from Eduardo Castex (EC) and Ingeniero Luiggi (LU) in La Pampa (central Argentina within the Chaco-Pampean Plain) ranged from 3 to 1326 µg l(-1) As. The pH range for the provinces of San Juan (7.2-9.7) and La Pampa (7.0-9.9) are in agreement with other published literature. The highest total arsenic concentrations were found in La Pampa well waters (both rural farms and pre-treated urban sources), particularly where there was high pH (typically > 8.2), conductivity (>2,600 µS cm(-1)) and TDS (>1,400 mg l(-1)). Reverse osmosis (RO) treatment of well waters in La Pampa for domestic drinking water in EC and LU significantly reduced total arsenic concentrations from a range of 216-224 µg l(-1) As to 0.3-0.8 µg l(-1) As. Arsenic species for both provinces were predominantly As(III) and As(V). As(III) and As(V) concentrations in San Juan ranged from 4-138 µg l(-1) to <0.02-22 µg l(-1) for surface waters (in the San José de Jáchal region) and 23-346 µg l(-1) and 0.04-76 µg l(-1) for groundwater, respectively. This translates to a relative As(III) abundance of 69-100% of the total arsenic in surface waters and 32-100% in groundwater. This is unexpected because it is typically thought that in oxidising conditions (surface waters), the dominant arsenic species is As(V). However, data from the SPE methodology suggests that As(III) is the prevalent species in San Juan, indicating a greater influence from reductive processes. La Pampa groundwater had As(III) and As(V) concentrations of 5-1,332 µg l(-1) and 0.09-592 µg l(-1) for EC and 32-242 µg l(-1) and 30-277 µg l(-1) As for LU, respectively. Detectable levels of MA(V) were reported in both provinces up to a concentration of 79 µg l(-1) (equating to up to 33% of the total arsenic). Previously published literature has focused primarily on the inorganic arsenic species, however this study highlights the potentially significant concentrations of organoarsenicals present in natural waters. The potential for separating and preserving individual arsenic species in the field to avoid transformation during transport to the laboratory, enabling an accurate assessment of in situ arsenic speciation in water supplies is discussed.

Field based speciation of arsenic in UK and Argentinean water samples.

A field method is reported for the speciation of arsenic in water samples that is simple, rapid, safe to use beyond laboratory environments, and cost effective. The method utilises solid-phase extraction cartridges (SPE) in series for selective retention of arsenic species, followed by elution and measurement of eluted fractions by inductively coupled plasma mass spectrometry (ICP-MS) for "total" arsenic. The method is suitable for on-site separation and preservation of arsenic species from water. Mean percentage accuracies (n = 25) for synthetic solutions of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MA), and dimethylarsinic acid (DMA) containing 10 µg l(-1) As, were 98, 101, 94, and 105%, respectively. Data are presented to demonstrate the effect of pH and competing anions on the retention of the arsenic species. The cartridges were tested in the UK and Argentina at sites where arsenic was known to be present in surface and groundwaters, respectively, at elevated concentrations and under challenging matrix conditions. In Argentinean groundwater, 4-20% of speciated arsenic was present as MA and 20-73% as As(III). In UK surface waters, speciated arsenic was measured as 7-49% MA and 12-42% DMA. Comparative data from the field method using SPE cartridges and the laboratory method using liquid chromatography coupled to ICP-MS for all water samples provided a correlation of greater than 0.999 for As(III) and DMA, 0.991 for MA, and 0.982 for As(V) (P < 0.01).

The effect of elevated dietary cholesterol on pulmonary surfactant function in adolescent mice.

It has been established that phospholipids and cholesterol interact in films of pulmonary surfactant (PS). Generally it is thought that phospholipids increase film stability whereas cholesterol increases film fluidity. To study this further, we modified dietary cholesterol in mice which received either standard rodent lacking cholesterol (sd), or high cholesterol (2%) diet (hc) for 1 month. Phospholipid stability was investigated by a capillary surfactometer (CS), which measures airflow resistance and patency. PS was collected by bronchiolar lavage and centrifuged to obtain the surface-active film (SAF). Results showed that the hc-SAF had significantly more cholesterol than sd-SAF. CS analyses at 37 degrees C showed no significance differences in airflow resistance between hc-SAF and sd-SAF. However, at 37 degrees C, sd-SAF showed greater ability to maintain patency compared to hc-SAF, whereas at 42 degrees C hc-SAF showed patency ability similar to sd-SAF. The results suggested that increased cholesterol in hc-SAF induced less stability in the SAF possibly due to cholesterol's fluidizing effect on phospholipids at physiological temperatures.

DNA fragmentation in developing lung fibroblasts exposed to Stachybotrys chartarum (atra) toxins.

Stachybotrys chartarum (atra) is a toxic mold that grows on water-damaged cellulose-based materials. Research has revealed also that inhalation of S. chartarum spores caused marked changes in respiratory epithelium, especially to developing lungs. We analyzed the epigenetic potential of S. chartarum spore toxins on developing rat lung fibroblasts using single cell gel electrophoresis (comet assay). Isolated fetal lung fibroblasts were exposed to S. chartarum spore toxins for 15 min, 3, 14, or 24 hr and control cells were exposed to saline under the same conditions. Cells were embedded in agarose, electrophoresed under alkaline conditions and silver stained. DNA damage was assessed in terms of fragmentation as measured by comet tail length (DNA migration) and intensity (% DNA contained within head and tail). Upon visual inspection, control fibroblasts showed no DNA fragmentation whereas S. chartarum-treated cells had definable comets of various degrees depending upon the time-course. Analyses of the comets revealed that exposure to S. chartarum spore toxins for at least 15 min to 14 hr, induced increased DNA fragmentation in a time-dependent manner. The fact that exposure to toxins for 24 hr showed less damage suggested that developing lung fibroblasts may have the capability of repairing DNA fragmentation.

Integration of microfluidics with biomedical infrared spectroscopy for analytical and diagnostic metabolic profiling.

We describe how infrared spectroscopy of dry films (IRDF) can provide diagnostic information, and how we expect integration with laminar fluid diffusion interface (LFDI) sample pre-processing to generate new analytical and diagnostic tests. LFDI pre-processing provides sample clean-up and analyte separation. The sensitivity of IRDF to certain analytes is enhanced through the depletion of sample constituents that otherwise obscure relevant spectral features, permitting the deposition of films with larger sample volumes and, hence, of greater effective optical pathlength for the targeted analytes. An integrated LFDI-IRDF technology holds promise both as a method for rapid point-of-care quantitative analysis of biological fluids and as the engine of discovery for a wide range of novel diagnostic methods based upon metabolic profiling. In particular, successful integration will provide a versatile and cost effective technology platform that will allow for the accurate quantification of low-concentration analytes that are otherwise inaccessible and will provide the basis for diagnostic and prognostic methods that would otherwise be impossible. The specific question addressed by the proof-of-concept study summarised here is whether the spectra of LFDI processed samples can provide analytical methods that are more accurate than otherwise possible without LFDI pre-processing. The enrichment of serum creatinine is accomplished, with subsequent enhancement of its spectral contribution permitting quantification of this clinically important analyte beyond that achievable with no pre-processing. Finally, to illustrate the potential in diagnostic applications, two recently initiated studies are outlined, one involving chronic kidney disease and the other for chronic and acute coronary artery disease.

Bioaccessibility of arsenic in soils developed over Jurassic ironstones in eastern England.

Jurassic ironstones outcropping over parts of eastern England give rise to soils with arsenic concentrations in excess of the UK soil guideline value of 20 mg kg(-1) for residential areas. Total arsenic concentrations were determined for 73 ironstone derived soils and bioaccessible arsenic determined using an in vitro physiologically based extraction test. The bioaccessible arsenic concentration for these soils was found to be well below the soil guideline value with a mean concentration of 4 mg kg(-1) and a range of 2-17 mg kg(-1). The bioaccessible fraction ranges from 1.2 to 33%. Data from a sequential extraction test based on the use of aqua regia as the main extractant is presented for a subset of 20 of the soils. Chemometric data reduction is used to demonstrate that the bioaccessible arsenic is mainly contained within calcium iron carbonate (sideritic) assemblages and only partially iron aluminosilicates, probably berthierine, and iron oxyhydroxide phases, probably goethite. It is suggested that the bulk of the non-bioaccessible arsenic is bound up with less reactive iron oxide phases.

Analysis of pulmonary surfactant by Fourier-transform infrared spectroscopy following exposure to Stachybotrys chartarum (atra) spores.

Lung cells are among the first tissues of the body to be exposed to air-borne environmental contaminants. Consequently the function of these cells may be altered before other cells are affected. As gas exchange takes place in the lungs, changes in cellular function may have serious implications for the processes of oxygen uptake and carbon dioxide elimination. In order for these processes to occur, the lung must maintain a high degree of expandability. This latter function is accomplished in part by the pulmonary surfactant which is synthesized and released by alveolar type II cells. Earlier studies have shown that exposure to gas phase materials such as smoke or organic solvents can alter the composition and function of the surfactant. The present study examines the ability of highly toxigenic mold spores to alter surfactant composition. Stachybotrys chartarum spores suspended in saline were instilled into mouse trachea as described earlier. After 24 h, the lungs were lavaged and the different processing stages of surfactant isolated by repeated centrifugation. Intracellular surfactant was isolated from the homogenized lung tissue by centrifugation on a discontinuous sucrose gradient. Samples were extracted into chloroform-methanol, dried and analyzed by Fourier-Transform infrared spectroscopy (FTIR). Exposure to S. chartarum induced an overall reduction of phospholipid among the three surfactant subfractions. The intermediate and spent surfactant fractions in particular were reduced to about half of the values observed in the saline-treated group. The relative distribution of phospholipid was also altered by spore exposure. Within the intracellular surfactant pool, higher levels of phospholipid were detected after spore exposure. In addition, changes were observed in the nature of the phospholipids. In particular strong intramolecular hydrogen bonding, together with other changes, suggested that spore exposure was associated with absence of an acyl chain esterified on the glycerol backbone, resulting in elevated levels of lysophospholipid in the samples. This study shows that mold spores and their products induce changes in regulation of both secretion and synthesis of surfactant, as well as alterations in the pattern of phospholipid targeting to the pulmonary surfactant pools.

Noninvasive assessment of cardiac ischemic injury using (87)Rb and (23)Na MR imaging, (31)P MR, and optical spectroscopy.

The aim of the study was to compare and analyze different noninvasive indices of cell damage in the isolated pig heart model of regional ischemia. We used (23)Na and (87)Rb MR imaging to evaluate Na(+)/K(+) balance, (31)P MR spectroscopy to measure energetics, and optical spectroscopy to assess oxymyoglobin (MbO(2)). Hearts were subjected to 120-min occlusion of the left anterior descending artery and were then reperfused for 120 min. Reperfusion resulted in an increase in (23)Na (37 +/- 18% of the posterior wall) and decrease in (87)Rb (55 +/- 15%) image intensities, partial recovery of PCr, ATP, the total phosphates, and MbO(2) in the anterior wall. The above changes are consistent with the irreversible cell damage in the anterior wall, confirmed by lack of staining with triphenyltetrazolium chloride. Changes in Na(+) and Rb(+) in the infarct area inversely correlated and their ratio is a more sensitive index of cell injury than either of them alone.

Comparison of infrared spectroscopic and fluorescence depolarization assays for fetal lung maturity.

OBJECTIVE: Infrared spectroscopic analysis of amniotic fluid was recently shown to be a potential useful method for the determination of fetal lung maturity. Those studies used thin-layer chromatography as a reference method for the calibration of the infrared-based technique. However, thin-layer chromatography is compromised by large intra-assay and interlaboratory coefficients of variation. Therefore in this study we have used a reference method that is based on fluorescence depolarization, the TDx FLM II assay, to verify the sensitivity and precision of infrared spectroscopy for assessment of fetal lung maturity status. STUDY DESIGN: Samples of amniotic fluid were obtained by amniocentesis from 101 patients between the 24th and 40th weeks of pregnancy. Small volumes (35 microL) of amniotic fluid specimens were dried, and the infrared spectra were measured with a commercial infrared spectrometer. The fetal lung surfactant/albumin ratio was determined separately for each specimen with the TDx FLM II assay. The proposed infrared method was then calibrated and tested with a partial least-squares regression analysis to quantitatively correlate the infrared spectra with the surfactant/albumin ratios provided by the TDx FLM II assays. RESULTS: A total of 144 training spectra were used to build the partial least-squares calibration model. The correlation coefficient for the training set was excellent (r = 0.92), with an SE between infrared-predicted and reference surfactant/albumin ratios of 17 mg/g. The model was then validated on a set of 69 test spectra and yielded an SE of 14 mg/g (r = 0.86). The final partial least-squares model included the 900- to 1500-cm(-1) and 2800- to 3200-cm(-1) spectral ranges and 6 partial least-squares factors. CONCLUSION: Because the infrared-based fetal lung maturity measurements correlated well with assays from both of the current standard clinical techniques (thin-layer chromatography and fluorescence depolarization) and the procedure is less labor and training intensive, we concluded that infrared spectroscopy has the potential to emerge as the method of choice for prediction of fetal lung maturity from amniotic fluid analysis.

In vivo optical/near-infrared spectroscopy and imaging of metalloproteins.

A number of medical applications of near-infrared spectroscopy are growing closer to clinical acceptance, and new techniques involving both spectroscopy and imaging are evolving rapidly. In vivo spectroscopy and, more recently, imaging techniques are largely based upon optical electronic transitions involving the metal centers of hemoglobin (blood), myoglobin (muscle) and cytochrome aa3 (mitochondria). The wide variety of near-IR based applications includes heart and stroke research, monitoring cerebral oxygenation of premature babies, and 'functional activation' (response of brain to mental tasks). All of these applications are founded upon changes in hemoglobin O2 saturation; these changes are monitored by following trends in the near-infrared absorptions of deoxyhemoglobin (760 nm) and oxyhemoglobin (920 nm). The same absorptions provide a basis for imaging regional variations in blood oxygenation. This report presents and discusses examples, both from the literature and from our recent work, of near-infrared spectroscopy and imaging in medical applications.

Calcium phosphate-containing precipitate and the carcinogenicity of sodium salts in rats.

Sodium saccharin, ascorbate and other sodium salts fed at high doses to rats produce urinary bladder urothelial cytotoxicity with consequent regenerative hyperplasia. For sodium salts that have been tested, tumor activity is enhanced when administered either alone or after a brief exposure to a known genotoxic bladder carcinogen. These sodium salts alter urinary composition of rats resulting in formation of an amorphous precipitate. We examined the precipitate to ascertain its composition and further delineate the basis for its formation in rat urine. Using scanning electron microscopy with attached X-ray energy dispersive spectroscopy, the principal elements present were calcium, phosphorus, minor amounts of silicon and sulfur. Smaller elements are not detectable by this method. Infrared analyses demonstrated that calcium phosphate was in the tribasic form and silicon was most likely in the form of silica. Small amounts of saccharin were present in the precipitate from rats fed sodium saccharin (<5%), but ascorbate was not detectable in the precipitate from rats fed similar doses of sodium ascorbate. Large amounts of urea and mucopolysaccharide, apparently chondroitin sulfate, were detected in the precipitate by infrared analysis. Chemical analyses confirmed the presence of large amounts of calcium phosphate with variably small amounts of magnesium, possibly present as magnesium ammonium phosphate crystals, present in urine even in controls. Small amounts of protein, including albumin and alpha(2u)-globulin, were also detected (<5% of the precipitate). Calcium phosphate is an essential ingredient of the medium for tissue culture of epithelial cells, but when present at high concentrations (>5 mM) it precipitates and becomes cytotoxic. The nature of the precipitate reflects the unique composition of rat urine and helps to explain the basis for the species specificity of the cytotoxic and proliferative effects of high doses of these sodium salts.

Infrared spectroscopy of exfoliated cervical cell specimens. Proceed with caution.

OBJECTIVE: To determine whether diagnostic information may be recovered from the infrared spectra of exfoliated cell specimens by using a novel spectral feature extraction method, in conjunction with linear and quadratic discriminant analysis, for spectral classification. STUDY DESIGN: Over 800 infrared spectra were included in the study, with corresponding clinical diagnoses based upon cytology and, when available, histology reports. Three sets of classification trials were carried out with the aim of distinguishing the spectra corresponding to normal specimens from CIN 1, 2 and 3. For each of these three cases, the procedure was to: (1) develop a set of provisional classification models using only a "training" subset of the spectra, and (2) test each provisional model by its ability to correctly predict the diagnoses on the basis of the remaining spectra. RESULTS: For optimal classification trials, training set classification accuracies were 68% for normal/CIN 1, 73% for normal/CIN 2 and 81% for normal/CIN 3; for the corresponding test sets the classification accuracies were 60%, 60% and 67%, respectively. CONCLUSION: The infrared spectra of exfoliated cervical cells carry information regarding the presence or absence of dysplasia, and that information is recoverable--albeit imperfectly at this stage--from the spectra of "real life" cell preparations.