412 research outputs found
SIMULTANEOUS ESTIMATION OF RELATED COMPOUNDS IN ESOMEPRAZOLE AND NAPROXEN TABLETS BY USING ION PAIR REVERSE PHASE HPLC
Objective: To develop and validate a novel gradient reverse phase HPLC method for quantitative estimation of Naproxen and Esomeprazole impurities in pharmaceutical dosage form.Methods: Chromatographic separation was achieved on X-Bridge C18,150x4.6 mm, 3.5 µm column. Detection wavelength was set at 302 nm. The mobile phase A consists of Buffer and Acetonitrile in the ratio of 90:10, where Buffer was prepared by dissolving di ammonium hydrogen phosphate (2.64 gm per Liter) and 1-hexane sulphonic acid sodium salt (1.0 gm per Liter), pH adjusted to 6.5±0.05 with orthophosphoric acid. A mixture of acetonitrile and 1-propanol in the ratio of 90:10 was used as mobile phase B. Flow rate was set to 0.7 mL/minute in gradient elution mode, with a retention time for Naproxen and Esomeprazole 29 and 46 minute respectively.Results: The calibration curve was linear over the concentration range of 4.621 µg/mL – 99.026 µg/mL for Naproxen and 0.254 µg/mL–3.806 µg/mL for Esomeprazole (r= 0.999). The proposed method was found to be (considered)accurate and precise and linear within the desired range. The limit of quantitation (LOQ) was calculated. The purity angle was found less than purity threshold for forced degradation peaks, which shows there was no interference from the common excipient, known impurities and degradents indicating separation, accuracy and reliability of the method. The method was validated as per ICH guidelines and found to be specific, accurate, linear, precise and stability indicating.Conclusion: A Novel, simple, selective and rapid reversed phase high performance liquid chromatographic (HPLC) method was developed and validated for the estimation of Naproxen and Esomeprazole impurities in pharmaceutical dosage form. Hence, the method can be used for routine analysis in various pharmaceutical industries.Â
Interstitial null-distance time-domain diffuse optical spectroscopy using a superconducting nanowire detector
Significance: Interstitial fiber-based spectroscopy is gaining interest for real-time in vivo optical biopsies, endoscopic interventions, and local monitoring of therapy. Different from other photonics approaches, time-domain diffuse optical spectroscopy (TD-DOS) can probe the tissue at a few cm distance from the fiber tip and disentangle absorption from the scattering properties. Nevertheless, the signal detected at a short distance from the source is strongly dominated by the photons arriving early at the detector, thus hampering the possibility of resolving late photons, which are rich in information about depth and absorption. Aim: To fully benefit from the null-distance approach, a detector with an extremely high dynamic range is required to effectively collect the late photons; the goal of our paper is to test its feasibility to perform TD-DOS measurements at null source-detector separations (NSDS). Approach: In particular, we demonstrate the use of a superconducting nanowire single photon detector (SNSPD) to perform TD-DOS at almost NSDS formula presented by exploiting the high dynamic range and temporal resolution of the SNSPD to extract late arriving, deep-traveling photons from the burst of early photons. Results: This approach was demonstrated both on Monte Carlo simulations and on phantom measurements, achieving an accuracy in the retrieval of the water spectrum of better than 15%, spanning almost two decades of absorption change in the 700- to 1100-nm range. Additionally, we show that, for interstitial measurements at null source-detector distance, the scattering coefficient has a negligible effect on late photons, easing the retrieval of the absorption coefficient. Conclusions: Utilizing the SNSPD, broadband TD-DOS measurements were performed to successfully retrieve the absorption spectra of the liquid phantoms. Although the SNSPD has certain drawbacks for use in a clinical system, it is an emerging field with research progressing rapidly, and this makes the SNSPD a viable option and a good solution for future research in needle guided time-domain interstitial fiber spectroscopy
Effects of chlorantraniliprole and thiamethoxam rice seed treatments on egg numbers and first instar survival of Lissorhoptrus oryzophilus (Coleoptera: Curculionidae)
Effects of treatment of rice seeds with an anthranilic diamide, chlorantraniliprole, and a neonicotinoid, thiamethoxam, on egg laying and first instar survival in rice water weevil, Lissorhoptrus oryzophilus Kuschel, were examined under greenhouse conditions. Exposure of adult weevils to rice (6-7 leaf stage) grown from seeds treated with chlorantraniliprole and thiamethoxam resulted in reduction in numbers of eggs and first instars. The low egg numbers by adults exposed to chlorantraniliprole-treated plants was confirmed as a sublethal effect on adults: adult survival was not impacted after 4 d of feeding on foliage from chlorantraniliprole-treated plants but the number of eggs laid by these weevils was reduced when released on untreated plants. Furthermore, a comparison of first instar emergence from chlorantraniliprole-treated plants and from untreated plants infested with weevils previously exposed to this chemical suggested that chlorantraniliprole was also reducing egg or first instar survival. In contrast, adults that fed on foliage from thiamethoxam-treated plants showed increased mortality. Possible sublethal effects of thiamethoxam on the number of eggs laid by adults were investigated by infesting untreated plants with weevils that survived exposure to thiamethoxam via foliar feeding (7 μg active ingredient / seed). Prior exposure to thiamethoxam through adult feeding reduced egg numbers. However, potential larvicidal or ovicidal effects of thiamethoxam seed treatments could not be detected in this study because of low first instar emergence from both thiamethoxam-treated plants and from untreated plants infested with weevils previously exposed to this chemical. These experiments revealed that the two seed treatments accomplish weevil control in different ways. © 2013 Entomological Society of America
Becoming a leader: catalysts and barriers to leader identity construction
In response to increased calls for research that can provide greater understanding of the relational and contextual issues surrounding leader identity construction processes, this qualitative study aims to provide insights into the subjective experience of constructing a leader identity within the context of organizations. Drawing on data from 50 semi-structured interviews, this paper focuses on significant sub-themes, which were grouped into two categories, namely identity catalysts (e.g. issues that participants identified as positively aiding in their leader identity construction process) and identity barriers (e.g. issues that participants identified as negatively impacting their leader identity construction process). These catalysts and barriers will be elaborated upon and their relationship to leader identity explained. This paper provides new insights into the leader identity construction process by using Leadership Identity Construction Theory as a lens for interpretation, and offers notable implications for theory, research and practice
Non-invasive investigation of adipose tissue by time domain diffuse optical spectroscopy
The human abdominal region is very heterogeneous and stratified with subcutaneous adipose tissue (SAT) being one of the primary layers. Monitoring this tissue is crucial for diagnostic purposes and to estimate the effects of interventions like caloric restriction or bariatric surgery. However, the layered nature of the abdomen poses a major problem in monitoring the SAT in a non-invasive way by diffuse optics. In this work, we examine the possibility of using multi-distance broadband time domain diffuse optical spectroscopy to assess the human abdomen non-invasively. Broadband absorption and reduced scattering spectra from 600 to 1100 nm were acquired at 1, 2 and 3 cm source-detector distances on ten healthy adult male volunteers, and then analyzed using a homogeneous model as an initial step to understand the origin of the detected signal and how tissue should be modeled to derive quantitative information. The results exhibit a clear influence of the layered nature on the estimated optical properties. Clearly, the underlying muscle makes a relevant contribution in the spectra measured at the largest source-detector distance for thinner subjects related to blood and water absorption. More unexpectedly, also the thin superficial skin layer yields a direct contamination, leading to higher water content and steeper reduced scattering spectra at the shortest distance, as confirmed also by simulations. In conclusion, provided that data analysis properly accounts for the complex tissue structure, diffuse optics may offer great potential for the continuous non-invasive monitoring of abdominal fat
Optical characterization of porcine tissues from various organs in the 650-1100 nm range using time-domain diffuse spectroscopy
We present a systematic characterization of the optical properties (µa and µs') of nine representative ex vivo porcine tissues over a broadband spectrum (650-1100 nm). We applied time-resolved diffuse optical spectroscopy measurements for recovering the optical properties of porcine tissues depicting a realistic representation of the tissue heterogeneity and morphology likely to be found in different ex vivo tissues. The results demonstrate a large spectral and inter-tissue variation of optical properties. The data can be exploited for planning or simulating ex vivo experiments with various biophotonics techniques, or even to construct artificial structures mimicking specific pathologies exploiting the wide assortment in optical properties.This article is freely available via Open Access. Click on the Publisher URL to access it via the publisher's site.Horizon 2020 Framework Programme10.13039/100010661 (654148;, 675332); Engineering and Physical Sciences Research Council10.13039/501100000266 (EP/R020965/1).published version, accepted versio
Time-domain NIRS system based on supercontinuum light source and multi-wavelength detection: Validation for tissue oxygenation studies
We present and validate a multi-wavelength time-domain near-infrared spectroscopy (TD-NIRS) system that avoids switching wavelengths and instead exploits the full capability of a supercontinuum light source by emitting and acquiring signals for the whole chosen range of wavelengths. The system was designed for muscle and brain oxygenation monitoring in a clinical environment. A pulsed supercontinuum laser emits broadband light and each of two detection modules acquires the distributions of times of flight of photons (DTOFs) for 16 spectral channels (used width 12.5 nm / channel), providing a total of 32 DTOFs at up to 3 Hz. Two emitting fibers and two detection fiber bundles allow simultaneous measurements at two positions on the tissue or at two source-detector separations. Three established protocols (BIP, MEDPHOT, and nEUROPt) were used to quantitatively assess the system's performance, including linearity, coupling, accuracy, and depth sensitivity. Measurements were performed on 32 homogeneous phantoms and two inhomogeneous phantoms (solid and liquid). Furthermore, measurements on two blood-lipid phantoms with a varied amount of blood and Intralipid provide the strongest validation for accurate tissue oximetry. The retrieved hemoglobin concentrations and oxygen saturation match well with the reference values that were obtained using a commercially available NIRS system (OxiplexTS) and a blood gas analyzer (ABL90 FLEX), except a discrepancy occurs for the lowest amount of Intralipid. In-vivo measurements on the forearm of three healthy volunteers during arterial (250 mmHg) and venous (60 mmHg) cuff occlusions provide an example of tissue monitoring during the expected hemodynamic changes that follow previously well-described physiologies. All results, including quantitative parameters, can be compared to other systems that report similar tests. Overall, the presented TD-NIRS system has an exemplary performance evaluated with state-of-the-art performance assessment methods
Enhanced diffuse optical tomographic reconstruction using concurrent ultrasound information
Multimodal imaging is an active branch of research as it has the potential to improve common medical imaging techniques. Diffuse optical tomography (DOT) is an example of a low resolution, functional imaging modality that typically has very low resolution due to the ill-posedness of its underlying inverse problem. Combining the functional information of DOT with a high resolution structural imaging modality has been studied widely. In particular, the combination of DOT with ultrasound (US) could serve as a useful tool for clinicians for the formulation of accurate diagnosis of breast lesions. In this paper, we propose a novel method for US-guided DOT reconstruction using a portable time-domain measurement system. B-mode US imaging is used to retrieve morphological information on the probed tissues by means of a semi-automatical segmentation procedure based on active contour fitting. A two-dimensional to three-dimensional extrapolation procedure, based on the concept of distance transform, is then applied to generate a three-dimensional edge-weighting prior for the regularization of DOT. The reconstruction procedure has been tested on experimental data obtained on specifically designed dual-modality silicon phantoms. Results show a substantial quantification improvement upon the application of the implemented technique.
This article is part of the theme issue ‘Synergistic tomographic image reconstruction: part 2’
- …