Publications by authors named "Littlejohn D"

Two dynamic versions of the simplified bioaccessibility extraction test (SBET) were developed-an off-line procedure and an on-line procedure coupled directly to ICP-MS. Batch, on-line, and off-line procedures were applied to simulated PM samples prepared by loading NIST SRM 2711A Montana II Soil and BGS RM 102 Ironstone Soil onto 45-mm TX40 filters widely used in air quality monitoring. Three real PM samples were also extracted.

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Process applications of mid-infrared (MIR) spectrometry may involve replacement of the spectrometer and/or measurement probe, which generally requires a calibration transfer method to maintain the accuracy of analysis. In this study, direct standardisation (DS), piecewise direct standardisation (PDS) and spectral space transformation (SST) were compared for analysis of ternary mixtures of acetone, ethanol and ethyl acetate. Three calibration transfer examples were considered: changing the spectrometer, multiplexing two probes to a spectrometer, and changing the diameter of the attenuated total reflectance (ATR) probe (as might be required when scaling up from lab to process analysis).

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The targeting task performance (TTP) model for prediction of target identification range suggests that boost filtering with a well-sampled, low-noise long-wave infrared (LWIR) sensor can substantially increase target ID range (by enhancing contrast at high spatial frequencies). We model a notional high-performance LWIR imaging system with a high F-number, deep electron wells, and a small-pitch focal plane array. System analysis performed with the Night Vision Integrated Performance Model (NVIPM) predicts that a range enhancement upwards of 50% is achievable with Wiener restoration applied to imagery from the modeled sensor.

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For the past year, the authors have been studying a long-wave infrared (LWIR) sensor design concept that combines high detector well capacity, small-pitch detectors, and digital image processing to optimize target acquisition. Theoretical performance modeling [via the Night Vision Integrated Performance Model (NVIPM)] suggests that our approach offers a large increase in target identification range, but multiple field trials using triangle orientation discrimination (TOD) have yielded results that are inconsistent with the model's predictions. For this reason, we have performed human perception experiments on simulated TOD targets, with and without image processing, to assess the utility of our approach and the value of TOD as an evaluation for digital image enhancement.

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Background: We previously reported the 5-year results of the phase 3 IBCSG 23-01 trial comparing disease-free survival in patients with breast cancer with one or more micrometastatic (≤2 mm) sentinel nodes randomly assigned to either axillary dissection or no axillary dissection. The results showed no difference in disease-free survival between the groups and showed non-inferiority of no axillary dissection relative to axillary dissection. The current analysis presents the results of the study after a median follow-up of 9·7 years (IQR 7·8-12·7).

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Background: Our retrospective review of prospectively collected data evaluated the efficacy of minimally invasive parathyroidectomy (MIP) and compared preoperative imaging modalities in a rural referral centre.

Methods: Patients with a diagnosis of primary hyperparathyroidism underwent surgeon-performed ultrasound (SUS) and technetium-99 m sestamibi (MIBI). Radiologist-performed ultrasound (RUS) was sought when the diagnosis remained in doubt.

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A novel two-step sequential extraction has been developed to assess the bioaccessibility of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in airborne particulate matter following inhalation and transport into the human gastrointestinal tract by mucociliary clearance. A new artificial mucus fluid (AMF) was used to determine the bioaccessible potentially toxic element (PTE) fraction in the upper airways, in sequence with the simplified bioaccessibility extraction test (SBET) or the stomach phase of the unified bioaccessibility method (gastric fluid only) (UBMG). Filter dynamic measurement system TX40 filters smeared with soil reference material (BGS RM 102) were used as test samples.

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A specially designed thermal vaporiser was used with a process mass spectrometer designed for gas analysis to monitor the esterification of butan-1-ol and acetic anhydride. The reaction was conducted at two scales: in a 150 mL flask and a 1L jacketed batch reactor, with liquid delivery flow rates to the vaporiser of 0.1 and 1.

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Transmission near-infrared (NIR) measurements of a 1 mm thick aspirin disk were made at different positions as it was moved through a stack of eight 0.5 mm thick disks of microcrystalline cellulose (Avicel). The magnitude of the first derivative of absorbance for the aspirin interlayer at 8934 cm(-1) was lower when the disk was placed at the top or bottom of the stack of Avicel disks, with the largest signal observed when the aspirin was positioned at the central positions.

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Objective: To measure the effectiveness of implementing the chronic care model (CCM) in improving HIV clinical outcomes.

Design: Multisite, prospective, interventional cohort study.

Setting: Two urban community health centres in Vancouver and Prince George, BC.

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Background: Novel analytical tools, which shorten the long and costly development cycles of biopharmaceuticals are essential. Metabolic flux analysis (MFA) shows great promise in improving our understanding of the metabolism of cell factories in bioreactors, but currently only provides information post-process using conventional off-line methods. MFA combined with real time multianalyte process monitoring techniques provides a valuable platform technology allowing real time insights into metabolic responses of cell factories in bioreactors.

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Background: For patients with breast cancer and metastases in the sentinel nodes, axillary dissection has been standard treatment. However, for patients with limited sentinel-node involvement, axillary dissection might be overtreatment. We designed IBCSG trial 23-01 to determine whether no axillary dissection was non-inferior to axillary dissection in patients with one or more micrometastatic (≤2 mm) sentinel nodes and tumour of maximum 5 cm.

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Article Synopsis
  • A 785nm diode laser was utilized to analyze the Raman spectra of powders, focusing on microcrystalline cellulose, aspirin, and sodium nitrate during mixing processes in a blender at 50rpm.
  • Two methods for evaluating the impact of particle characteristics on Raman sampling depth were compared, revealing that factors like particle size and shape influenced the "information" and "infinitely thick" depth values for the compounds examined.
  • The Raman spectroscopy approach allowed for non-invasive monitoring of aspirin blending into Avicel, identifying mixing endpoints and concentrations in real-time, while also generating compound-specific mixing profiles that were compared to other techniques such as near infrared (NIR) spectrometry.
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Despite the existence of various methods to remove cosmic spikes from Raman data, only a few of them are suitable for process Raman spectroscopy. The disadvantages of these algorithms include increased analysis time, low accuracy of spike detection, or reliance on variable parameters that must be chosen by trial and error in each case. We demonstrate a novel approach to detecting cosmic spikes in process Raman data and validate it using a wide range of experimental data.

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Introduction: International evidence shows that enhancement of primary health care (PHC) services for disadvantaged populations is essential to reducing health and health care inequities. However, little is known about how to enhance equity at the organizational level within the PHC sector. Drawing on research conducted at two PHC Centres in Canada whose explicit mandates are to provide services to marginalized populations, the purpose of this paper is to discuss (a) the key dimensions of equity-oriented services to guide PHC organizations, and (b) strategies for operationalizing equity-oriented PHC services, particularly for marginalized populations.

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A total of 383 tablets of a pharmaceutical product were analyzed by backscatter and transmission Raman spectrometry to determine the concentration of an active pharmaceutical ingredient (API), chlorpheniramine maleate, at the 2% m/m (4 mg) level. As the exact composition of the tablets was unknown, external calibration samples were prepared from chlorpheniramine maleate and microcrystalline cellulose (Avicel) of different particle size. The API peak at 1594 cm(-1) in the second derivative Raman spectra was used to generate linear calibration models.

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Transmission Raman measurements of a 1 mm thick sulfur-containing disk were made at different positions as it was moved through 4 mm of aspirin (150-212 μm) or microcrystalline cellulose (Avicel) of different size ranges (<38, 53-106, and 150-212 μm). The transmission Raman intensity of the sulfur interlayer at 218 cm(-1) was lower when the disk was placed at the top or bottom of the powder bed, compared to positions within the bed and the difference between the sulfur intensity at the outer and inner positions increased with Avicel particle size. Also, the positional intensity difference was smaller for needle-shaped aspirin than for granular Avicel of the same size.

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Particle size distribution and compactness have significant confounding effects on Raman signals of powder mixtures, which cannot be effectively modeled or corrected by traditional multivariate linear calibration methods such as partial least-squares (PLS), and therefore greatly deteriorate the predictive abilities of Raman calibration models for powder mixtures. The ability to obtain directly quantitative information from Raman signals of powder mixtures with varying particle size distribution and compactness is, therefore, of considerable interest. In this study, an advanced quantitative Raman calibration model was developed to explicitly account for the confounding effects of particle size distribution and compactness on Raman signals of powder mixtures.

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Analysis of needle-shaped particles of cellobiose octaacetate (COA) obtained from vacuum agitated drying experiments was performed using three particle size analysis techniques: laser diffraction (LD), focused beam reflectance measurements (FBRM) and dynamic image analysis. Comparative measurements were also made for various size fractions of granular particles of microcrystalline cellulose. The study demonstrated that the light scattering particle size methods (LD and FBRM) can be used qualitatively to study the attrition that occurs during drying of needle-shaped particles, however, for full quantitative analysis, image analysis is required.

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Introduction: One important goal of strengthening and renewal in primary healthcare (PHC) is achieving health equity, particularly for vulnerable populations. There has been a flurry of international activity toward the establishment of indicators relevant to measuring and monitoring PHC. Yet, little attention has been paid to whether current indicators: 1) are sensitive enough to detect inequities in processes or outcomes of care, particularly in relation to the health needs of vulnerable groups or 2) adequately capture the complexity of delivering PHC services across diverse groups.

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Recently, transmission Raman spectroscopy has been shown to be a valuable tool in the volumetric quantification of pharmaceutical formulations. In this work a Monte Carlo simulation and experimental study are performed to elucidate the dependence of the Raman signal on depth from the viewpoint of probing pharmaceutical tablets and powders in this experimental configuration. The transmission Raman signal is shown to exhibit a moderate bias toward the center of the tablets and this can be considerably reduced by using a recently developed Raman signal-enhancing concept, the "photon diode.

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Article Synopsis
  • - The study explored the evaporation of methanol from cellobiose octaacetate particles using Raman spectrometry in a vacuum drier, focusing on optimizing drying conditions for efficiency.
  • - A design of experiments approach was applied to examine the impacts of agitation method, solvent loss percentage, and jacket temperature on drying time and particle attrition.
  • - Results showed real-time monitoring of drying stages through Raman signals, although direct correlations between particle size and in situ Raman data were limited due to variations caused by particle motion and bulk density changes.
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Two methods of analysis were developed to permit detection of counterfeit Scotch whisky samples using a novel attenuated total reflectance (ATR) diamond-tipped immersion probe for mid-infrared (MIR) spectrometry. The first method allowed determination of the ethanol concentration (35-45% (v/v)) in situ without dilution of the samples; the results obtained compared well with the supplied concentrations (average relative error of 1.2% and 0.

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In quantitative on-line/in-line monitoring of chemical and bio-chemical processes using spectroscopic instruments, multivariate calibration models are indispensable for the extraction of chemical information from complex spectroscopic measurements. The development of reliable multivariate calibration models is generally time-consuming and costly. Therefore, once a reliable multivariate calibration model is established, it is expected to be used for an extended period.

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Large-scale commercial bioprocesses that manufacture biopharmaceutical products such as monoclonal antibodies generally involve multiple bioreactors operated in parallel. Spectra recorded during in situ monitoring of multiple bioreactors by multiplexed fiber-optic spectroscopies contain not only spectral information of the chemical constituents but also contributions resulting from differences in the optical properties of the probes. Spectra with variations induced by probe differences cannot be efficiently modeled by the commonly used multivariate linear calibration models or effectively removed by popular empirical preprocessing methods.

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