Near-infrared (NIR) reflectance spectra for mixtures of ordered kaolinite and ordered dickite have been found to simulate the spectral response of disordered kaolinite. The amount of octahedral vacancy disorder in nine disordered kaolinite samples was estimated by comparing the sample spectra to the spectra of reference mixtures. The resulting estimates are consistent with previously published estimates of vacancy disorder for similar kaolin minerals that were modeled from calculated X-ray diffraction patterns. The ordered kaolinite and dickite samples used in the reference mixtures were carefully selected to avoid undesirable particle size effects that could bias the spectral results.

NIR spectra were also recorded for laboratory mixtures of ordered kaolinite and halloysite to assess whether the spectra could be potentially useful for determining mineral proportions in natural physical mixtures of these two clays. Although the kaolinite-halloysite proportions could only be roughly estimated from the mixture spectra, the halloysite component was evident even when halloysite was present in only minor amounts. A similar approach using NIR spectra for laboratory mixtures may have applications in other studies of natural clay mixtures.

The potential of near-infrared (NIR) spectroscopy to track the adsorption of water on montmorillonite saturated with different exchangeable cations is demonstrated in the present study. The Na+, K+, Ca2+, and Mg2+ forms of JP montmorillonite (Jelšový Potok, Slovakia) were first dried and then hydrated at 23, 52, 88, and 100% relative humidity (RH). The combination band of water molecules, $(\nu +\delta {)}_{H_{2}O}$$\end{document}, allowed the study of the effect of exchangeable cations on the strength of H bonds between water molecules and on the amount of adsorbed water. With increasing ionic potential (IP) of the exchangeable cation, the strength of the H bonds increased and the $(\nu +\delta {)}_{H_{2}O}$\$\end{document} band was shifted to lower wavenumbers. The area of the $(\nu +\delta {)}_{H_{2}O}$\$\end{document} band, corresponding to the amount of adsorbed water, was compared with results from gravimetry. The good correlation (R2 > 0.97) between the two independent methods confirmed that the $(\nu +\delta {)}_{H_{2}O}$\$\end{document} band area reflected reasonably well the amount of H2O in montmorillonite. The peak-fitting analysis of the $(\nu +\delta {)}_{H_{2}O}$\$\end{document} band allowed differentiation of weakly and strongly H-bonded water molecules. The position of the high-frequency component at 5260–5250 cm−1, related to H2O weakly H-bonded to basal oxygens of the tetrahedral sheets, was influenced only slightly by the exchangeable cations. Two low-frequency components were assigned to the combination modes involving asymmetric (ν3) and symmetric (ν1) stretching vibrations of strongly H-bonded H2O. Only the $({\nu }_1+\delta {)}_{H_{2}O}$\$\end{document} component (5055–5000 cm−1) showed significant dependence on the type of exchangeable cation and hydration level. Peak-fit analysis revealed a small effect of the type of exchangeable cation on the amount of water molecules weakly H-bonded to the siloxane surface but a pronounced effect on the content of strongly hydrogen-bonded H2O. The amount of weakly H-bonded H2O remained stable after reaching a certain level of hydration, but a gradual increase in the strongly H-bonded water molecules with increasing RH was observed.

The octahedral composition of palygorskite in more than 300 samples from the Pefkaki deposit, W. Macedonia, Greece, has been studied by near-infrared (NIR) and X-ray diffraction (XRD), and evaluated according to the formula $y{\text{Mg}}_5{\text{Si}}_8{\text{O}}_{20}{\left(\text{OH}\right)}_2\cdot x{\text{Mg}}_2{\text{Fe}}_{\text{2}}^{\text{III}}{\text{Si}}_8{\text{O}}_{20}{\left(\text{OH}\right)}_2\cdot \left(1-x-y\right)$ Mg2Al2Si8O20(OH)2. Included in the study were PFl-1 and several commercial palygorskites. Our analysis of 2nd derivative NIR spectra shows that the dioctahedral composition is adequately described by three sharp overtone bands representing AlAlOH, AlFeIIIOH and FeIIIFeIIIOH in M2 dioctahedral sites, and that the summed intensity of these bands is proportional to the amount of dioctahedral component present (1−y). The samples show large variations in the degree of dioctahedral FeIII-for-Al substitution with FeIII occupying up to 70% of the dioctahedral M2 sites. Ternary analysis shows that the distribution of dioctahedral Al and FeIII is not random, but displays a tendency towards homoionic pairing. An overtone band at 7214 cm−1 and several combination bands are indicative of a trioctahedral Mg3OH component (y), and their appearance correlates with a distinct palygorskite signature in thermogravimetric analysis. Nevertheless, these bands cannot be used reliably for the quantification of a trioctahedral palygorskite component due to their close similarity to those of sepiolite. To circumvent this problem, we have evaluated y indirectly by calculating the difference between 1−y and the total concentration of palygorskite determined by the normalized intensity of the d110 XRD peak of palygorskite at 10.4 Å. Using this methodology, we have found that the samples conform to a trioctahedral limit of y ≈ 0.55, although within this limit they display large variations in octahedral character. Finally, we extend the above methodology to PLS chemometrics and show how NIR can be used to determine palygorskite content routinely in multimineralic geological samples.

The Swiss trials on medical prescription of injectable diacetylmorphine (pharmaceutical heroin) for “severe” heroin dependence provoked very controversial commentaries. Despite methodological shortcomings, the evaluation of the Swiss heroin trials yielded some interesting findings. Study participants showed substantial improvements in health and well-being and noticeable declines in illicit drug use and criminal activities. Heroin prescription may thus be helpful for some of those who continue to regularly use illicit heroin while maintained on methadone or who refuse other available treatment options. However, research-based evidence suggests that the intravenous (IV) application of heroin under medical supervision may have untoward side effects. Recent studies have shown that heroin injections produce transient, but significant decreases in systemic and cortical oxygenation most likely secondary to respiratory depression. Among others, these effects are the subject of ongoing studies.

Introduction: Near-infrared spectroscopy (NIRS) can be used to monitor the oxygen saturation of hemoglobin in any given superficial tissue. However, the measurements provided by different oximeters can vary a lot. Little is known about the specific patient characteristics that could affect the inter-device agreement of tissular oximeters. This study aimed to evaluate the association between the quantity of subcutaneous fat (assessed by skinfold thickness) and the inter-device agreement of two tissue oximeters, the INVOS 5100c and the Equanox 7600. Methods: In this prospective cohort study, tissue saturations and skinfold thickness were measured at four different sites on both sides of the body in healthy adult (≥18 years old) volunteers. The association between the quantity of subcutaneous fat (assessed by skinfold thickness) and the inter-device agreement (absolute difference between the oximetry values provided by the two oximeters) was first assessed with a Pearson's correlation and a scatter plot. Subsequently, a linear mixed model was used to evaluate the impact of the subcutaneous fat and other covariables (age, sex) on the inter-device agreement while adjusting for the repeated measurements across different sites for the same volunteers. Results: From January to March 2015, 53 healthy volunteers were included in this study with ages ranging between 20 and 81 years old, on which a total of 848 measures were taken. Higher skinfold measures were associated with an increase in the difference between measures provided by both oximeters (Slope = -0.59, Pearson correlation coefficient = -0.51, p < 0.001). This observed association persisted in a linear mixed model (-0.48 [95% confidence interval {CI}-0.61 to -0.36], p < 0.001). The sex of the volunteers also influenced the inter-oximeter agreement (Women:-5.77 [95%CI -8.43 to -3.11], p < 0.001), as well as the forearm sites (Left forearm: −7.16 [95%CI -9.85 to –4.47], p < 0.001; right forearm: −7.01 [95%CI -9.61 to −4.40], p < 0.001). Conclusion: The quantity of subcutaneous fat, as well as the sex of the volunteers and the measurement sites, impacted the inter-device agreement of two commonly used oximeters. Given these findings, monitoring using tissue oximetry should be interpreted with great care when there is a significant quantity of subcutaneous fat.

Introduction: Near-infrared spectroscopy (NIRS) is a non-invasive, continuous and painless method of monitoring oxygen saturation of hemoglobin in any given superficial tissue. Given that hemodynamic instability can affect the oxygen saturation, NIRS could prove to be an interesting tool in quantifying tissue oxygenation, consequently guiding clinical management. The aim of this study was to compare the reliability of two commonly used tissue oximeters, the INVOS 5100c from Covidien and the Equanox 7600 from Nonin. We postulated the Equanox (a more recent tissue oximeter) would have a better reliability than the INVOS. As a secondary outcome, we evaluated whether the measures given by the two oximeters were comparable. Methods: The study population was composed of healthy adult volunteers. Three measurements were taken at six different sites on both sides of the body in a randomized order. Two different sensors were used for each measure. From these measures, two intra-class correlations (ICC) - one inter-sensor and the other intra-sensor - were calculated for each device and compared using the Fisher’s r-to-z transformation method. An additional inter-device ICC was also calculated. We considered ICCs over 0.75 as an indicator of good reliability, while ICCs under 0.40 were considered to represent poor reliability. The sample size was calculated based on the calculation of a unidirectional confidence interval for a parametric ICC. Expecting a 0.75 ICC value, we concluded that 53 participants needed to be recruited in order to attain 80% power and a range of 0.1 towards the low values. Results: Fifty-three healthy volunteers (27 men and 26 women) with a mean age of 31 years (standard deviation 10) were recruited. We found no differences between the repeatability of the INVOS and the Equanox for both inter and intra-sensor reliability (ICC=0.94 (95% confidence interval (CI) 0.86-0.97) versus ICC=0.92 (95%CI 0.86-0.95), p=0.42 and ICC=0.94 (95%CI 0.89-0.96) versus ICC=0.96 (95%CI 0.93-0.98), p=0.21, respectively). However, when compared directly, we found that the readings produced by the two oximeters varied considerably (ICC 0.18 (95%CI -0.10 to 0.43). Conclusion: When taken individually, both tissue oximeters displayed good inter and intra-sensor reliability. However, they oximeters displayed poor inter-devices agreement, their readings varying considerably amongst each other.

Introduction: Tissue oximetry using near-infrared spectroscopy (NIRS) is a non-invasive monitor of cerebral oxygenation. This new technology has been used during cardiac arrest because of its ability to give measures in low blood flow situations. The aim of this systematic review was to assess the evidence regarding the association between NIRS values and resuscitation outcomes in patients undergoing cardiopulmonary resuscitation. We hypothesized that higher NIRS values would be associated with better outcomes and that the strength of that association would differ depending on the timing of the NIRS measurements. Methods: This review was registered (Prospero CRD42015017380) and is reported as per the PRISMA guidelines. Medline, Embase and CENTRAL were searched from their inception to September 18th, 2015 using a specifically designed search strategy. Grey literature was also searched using Web of Science and Google Scholar. NIRS manufacturers and authors of included citations were contacted to inquire on unpublished results. Finally, the references of all retained articles were reviewed in search of additional relevant studies. Studies reporting NIRS monitoring in adults during cardiac arrest were eligible for inclusion. Case reports and case series of fewer than five patients were automatically excluded. Two reviewers assessed the quality of included articles and extracted the data. Results: Out of 3275 unique citations, 19 non-randomized observational studies (15 articles and four conference abstracts) were included in this review, for a total of 2436 patients. Six studies were evaluated at low risk of bias, nine at intermediate risk and four at high risk. We found a stronger association between the return of spontaneous circulation (ROSC) and the highest NIRS value measured during resuscitation (standard mean deviation (SMD) 3.46 (95%CI 2.31-4.62)) than between ROSC and the mean NIRS measures (SMD 1.33 (95%CI 0.92-1.74)) which was superior to the one between ROSC and initial measures (SMD 0.45 (95%CI 0.02-0.88)). Conclusion: Patients with good outcomes have significantly higher NIRS value during resuscitation than their counterparts. The association between ROSC and NIRS measurements was influenced the timing of measurements during resuscitation.

We hypothesised that lower mesenteric near-infrared spectroscopy values would be associated with a greater incidence of gastrointestinal complications in children weighing <10 kg who were recovering from cardiac surgery. We evaluated mesenteric near-infrared spectroscopy, central venous oxygen saturation, and arterial blood gases for 48 hours post-operatively. Enteral feeding intake, gastrointestinal complications, and markers of organ dysfunction were monitored for 7 days. A total of 50 children, with median age of 16.7 (3.2–31.6) weeks, were studied. On admission, the average mesenteric near-infrared spectroscopy value was 71±18%, and the systemic oxygen saturation was 93±7.5%. Lower admission mesenteric near-infrared spectroscopy correlated with longer time to establish enteral feeds (r=−0.58, p<0.01) and shorter duration of feeds at 7 days (r=0.48, p<0.01). Children with gastrointestinal complications had significantly lower admission mesenteric near-infrared spectroscopy (58±18% versus 73±17%, p=0.01) and higher mesenteric arteriovenous difference of oxygen at admission [39 (23–47) % versus 19 (4–27) %, p=0.02]. Based on multiple logistic regression, admission mesenteric near-infrared spectroscopy was independently associated with gastrointestinal complications (Odds ratio, 0.95; 95% confidence interval, 0.93–0.97; p=0.03). Admission mesenteric near-infrared spectroscopy showed an area under the receiver operating characteristic curve of 0.76 to identify children who developed gastrointestinal complications, with a suggested cut-off value of 72% (78% sensitivity, 68% specificity). In this pilot study, we conclude that admission mesenteric near-infrared spectroscopy is associated with gastrointestinal complications and enteral feeding tolerance in children after cardiac surgery.

Objective: To establish whether the use of near-infrared spectroscopy is potentially beneficial in high-risk cardiac infants in United Kingdom paediatric intensive care units. Design: A prospective observational pilot study. Setting: An intensive care unit in North West England. Patients: A total of 10 infants after congenital heart surgery, five with biventricular repairs and five with single-ventricle physiology undergoing palliation. Interventions: Cerebral and somatic near-infrared spectroscopy monitoring for 24 hours post-operatively in the intensive care unit. Measurement and main results: Overall, there was no strong correlation between cerebral near-infrared spectroscopy and mixed venous oxygen saturation (r=0.48). At individual time points, the correlation was only strong (r=0.74) 1 hour after admission. The correlation was stronger for the biventricular patients (r=0.68) than single-ventricle infants (r=0.31). A strong inverse correlation was demonstrated between cerebral near-infrared spectroscopy and serum lactate at 3 of the 5 post-operative time points (1, 4, and 12 hours: r=−0.76, −0.72, and −0.69). The correlation was stronger when the cerebral near-infrared spectroscopy was <60%. For cerebral near-infrared spectroscopy <60%, the inverse correlation with lactate was r=−0.82 compared with those cerebral near-infrared spectroscopy >60%, which was r=−0.50. No correlations could be demonstrated between (average) somatic near-infrared spectroscopy and serum lactate (r=−0.13, n=110) or mixed venous oxygen saturation and serum lactate. There was one infant who suffered a cardiopulmonary arrest, and the cerebral near-infrared spectroscopy showed a consistent 43 minute decline before the event. Conclusions: We found that cerebral near-infrared spectroscopy is potentially beneficial as a non-invasive, continuously displayed value and is feasible to use on cost-constrained (National Health Service) cardiac intensive care units in children following heart surgery.