The Experts below are selected from a list of 6660 Experts worldwide ranked by ideXlab platform
Martin Wolf - One of the best experts on this subject based on the ideXlab platform.
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can the assessment of spontaneous oscillations by near Infrared Spectrophotometry predict neurological outcome of preterm infants
Advances in Experimental Medicine and Biology, 2016Co-Authors: Andre Stammwitz, Kurt Von Siebenthal, H U Bucher, Martin WolfAbstract:The aim was to assess the correlation between cerebral autoregulation and outcome. Included were 31 preterm infants, gestational age 26 1/7 to 32 2/7 and <24 h life. Coherence between cerebral total haemoglobin (tHb) or oxygenation index (OI) measured by near-Infrared Spectrophotometry (NIRS) and systemic heart rate (HR) or arterial blood pressure (MAP) was calculated as a measure of autoregulation. In contrast to previous studies, low coherences in the first 24 h were significantly associated with intraventricular haemorrhage, death or abnormal neurodevelopmental outcome at 18 months or later. We suggest that our results can be explained by the concept of a multi-oscillatory-functions-order.
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speech therapy changes blood circulation and oxygenation in the brain and muscle a near Infrared Spectrophotometry study
Advances in Experimental Medicine and Biology, 2009Co-Authors: Martin Wolf, Dietrich Von Bonin, Ursula WolfAbstract:Recently it has been shown that artistic speech therapy (AST) has effects on heart rate variability. The aim of this pilot study was to investigate whether AST also affects hemodynamics and tissue oxygenation in the brain and skeletal muscle measured by near Infrared Spectrophotometry(NIRS). The results show thatATS has effects on important physiological parameters, i.e., it leads to a decrease in cerebral blood flow during recitation and to brain activation thereafter.
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do gsm 900mhz signals affect cerebral blood circulation a near Infrared Spectrophotometry study
Optics Express, 2006Co-Authors: Martin Wolf, G. Morren, Daniel Haensse, Juerg FroehlichAbstract:Effects of GSM 900MHz signals (EMF) typical for a handheld mobile phone on the cerebral blood circulation were investigated using near-Infrared Spectrophotometry (NIRS) in a three armed (12W/kg, 1.2W/kg, sham), double blind, randomized crossover trial in 16 healthy volunteers. During exposure we observed borderline significant short term responses of oxyhemoglobin and deoxyhemoglobin concentration, which correspond to a decrease of cerebral blood flow and volume and were smaller than regular physiological changes. Due to the relatively high number of statistical tests, these responses may be spurious and require further studies. There was no detectable dose-response relation or long term response within 20min. The detection limit was a fraction of the regular physiological changes elicited by functional activation. Compared to previous studies using PET, NIRS provides a much higher time resolution, which allowed investigating the short term effects efficiently, noninvasively, without the use of radioactive tracers and with high sensitivity.
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A new multichannel near Infrared Spectrophotometry system for functional studies of the brain in adults and neonates.
Optics express, 2005Co-Authors: Daniel Haensse, Derek W. Brown, Hans Ulrich Bucher, Peter Szabo, Jean-claude Fauchère, Peter Niederer, Martin WolfAbstract:We have designed a versatile, multi-channel near-Infrared Spectrophotometry (NIRS) instrument for the purpose of mapping neuronal activation in the neonatal and adult brain in response to motor, tactile, and visual stimulation. The optical linearity, stability, and high signal to noise ratio (>70 dB) of the instrument were demonstrated using an in vitro validation procedure. In vivo measurements on the adult forearm were also performed. Changes in oxygenation, induced by arterial occlusion of the forearm, were recorded and were shown to compare well with measurements acquired using a conventional NIRS instrument. To demonstrate the capabilities of the instrument, functional measurements in adults and neonates were performed. The instrument exhibited the capability to differentiate with a spatial resolution in the order of cm, local activation patterns associated with a finger tapping sequence.
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Regional differences of cerebral hemoglobin concentration in preterm infants measured by near Infrared Spectrophotometry.
Technology and health care : official journal of the European Society for Engineering and Medicine, 1999Co-Authors: M. Keel, Vera Dietz, Martin Wolf, Kurt Von Siebenthal, Oskar Baenziger, Hans Ulrich BucherAbstract:Near Infrared Spectrophotometry has been used to measure total cerebral hemoglobin concentration (micromol/l) as a major indicator of the oxygen transport capacity in neonates. The aim of this study was to find out how the position of the probe influences the quality of the measurement and the actual cerebral hemoglobin concentration-values. We studied 10 healthy preterm infants with a mean gestational age of 31.5 weeks and a birthweight of 1513 g. The data were collected by a two channel near Infrared Spectrophotometry system using a geometrical principle to measure absolute cerebral hemoglobin concentration. The incoming signal of the light emitting diode as a value allows a prediction of the quality of the measurement: a high value refers to a high signal/noise ratio. Starting from the centre of the forehead (0%) for each measurement the probe was moved by 2.5% of the headcircumference to the left respectively right side of the head up to 20%. The cerebral hemoglobin concentration-values increased from 87 respectively 93 micromol/l up to 164 respectively 173 micromol/l on the right respectively left side, while the light emitting diode signal-values decreased from 21 respectively 21 down to 10 respectively 11, the more laterally the probe was moved. There were two plateaus of these variables in the frontal (0-5%) respectively lateral (15-20%) region. A further investigation on a solid phantom for premature heads showed that hair has either no or a contrary effect on the cerebral hemoglobin concentration-values than expected. The extracerebral tissue (soft tissue, skull, cerebrospinal fluid layer) is discussed to have a significant influence on the light attenuation in adult heads. Still there is no evidence for a significant effect on prematures, because this overlying tissue is much thinner and more translucent than the one in adults. Absolute cerebral hemoglobin concentration measured by near Infrared Spectrophotometry is substantially influenced by the position of the probe at the infant's head. Considering our results we recommend placing the probe at 2.5% of the headcircumference away from the centre of the forehead for the measurement of cerebral hemoglobin concentration in premature infants.
Dave K. Verma - One of the best experts on this subject based on the ideXlab platform.
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a method for determining crystalline silica in bulk samples by fourier transform Infrared Spectrophotometry
Annals of Occupational Hygiene, 2002Co-Authors: Dave K. Verma, Diane M Johnson, Karen Des TombeAbstract:A method for determining crystalline silica (α-quartz) in bulk samples has been developed. This procedure requires the bulk sample to be homogenized and sieved down to particle sizes <10 µm in diameter. The obtained fraction is analysed by Fourier transform Infrared Spectrophotometry. Method validation was carried out using 55 real-world bulk samples, containing between 1 and 75% (w/w) α-quartz. The method is capable of quantifying α-quartz down to 1% (w/w) in routine analysis. However, the method is unlikely to allow routine quantification at 0.1% (w/w) as currently mandated by regulations.
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a comparison of international silica α quartz calibration standards by fourier transform Infrared Spectrophotometry
Annals of Occupational Hygiene, 2001Co-Authors: Dave K. Verma, Don S. ShawAbstract:Seven international silica (alpha-quartz) standards were examined for relative purity to the US National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1878 Respirable alpha-quartz by Fourier Transform-Infrared Spectrophotometry (FT-IR). The standards examined have been used in North America, the UK, Australia and Germany. The 189 samples analyzed included NIST-SRM 1878, Min-U-Sil 5, Ottawa Silica Sand, Sikron F-600, A9950 (AUST 1), DQ12-Robock, DQ12-Bergbau. Size distributions of the standards were determined by Coulter Counter to be broadly similar with equivalent spherical volume median diameter ranging between 1.2 and 3 microm. The results showed the standards to differ by as much as 30% in relative purity. Consequently, an internationally agreed upon calibration standard is urgently needed. Min-U-Sil 5 based NIST-SRM 1878 or Sikron F-600 are the two most likely candidates. Any agreed standard must have a well characterized size distribution and closely match the respirable dust criteria. It should also be studied by both Infrared Spectrophotometry and X-ray diffraction techniques.
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A comparison of international silica (α-quartz) calibration standards by Fourier transform–Infrared Spectrophotometry
The Annals of occupational hygiene, 2001Co-Authors: Dave K. Verma, Don S. ShawAbstract:Seven international silica (alpha-quartz) standards were examined for relative purity to the US National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1878 Respirable alpha-quartz by Fourier Transform-Infrared Spectrophotometry (FT-IR). The standards examined have been used in North America, the UK, Australia and Germany. The 189 samples analyzed included NIST-SRM 1878, Min-U-Sil 5, Ottawa Silica Sand, Sikron F-600, A9950 (AUST 1), DQ12-Robock, DQ12-Bergbau. Size distributions of the standards were determined by Coulter Counter to be broadly similar with equivalent spherical volume median diameter ranging between 1.2 and 3 microm. The results showed the standards to differ by as much as 30% in relative purity. Consequently, an internationally agreed upon calibration standard is urgently needed. Min-U-Sil 5 based NIST-SRM 1878 or Sikron F-600 are the two most likely candidates. Any agreed standard must have a well characterized size distribution and closely match the respirable dust criteria. It should also be studied by both Infrared Spectrophotometry and X-ray diffraction techniques.
J. C. Protois - One of the best experts on this subject based on the ideXlab platform.
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comparison of direct x ray diffraction and Infrared Spectrophotometry and indirect Infrared Spectrophotometry methods for the analysis of α quartz in airborne dusts
Annals of Occupational Hygiene, 2005Co-Authors: E. Kauffer, A. Masson, Jean-claude Moulut, T. Lecaque, J. C. ProtoisAbstract:In this study, the a-quartz contents measured by different analytical techniques (X-ray diffraction, direct method; and Infrared Spectrophotometry, direct and indirect methods) were compared. The analyses were carried out on filters sampled in an industrial setting by means of a Dorr-Oliver cyclone. To verify the methodology used, filters loaded with pure a-quartz were also analysed. By and large, the agreement between the two direct methods was close on average, but on the basis of a comparison of the individual results, considerable differences exist. In absolute value, the mean relative deviation between the two techniques was <25% in only 47.8% of the cases. The results obtained by the indirect method (Infrared) were on average 13% lower than the results obtained by the two direct methods with a more important difference (23%) for samples where calcite was identified by X-ray diffraction in comparison with those where it was not (8%). This underestimation, which was not owing to dust losses during preparation, is probably explained by the elimination of organic compounds during dust calcinations or by the transformation of mineral compounds. The indirect method introduces additional sample handling operations with more risk of material loss. When the quantity of calcined material was <0.4 mg, the weighing operations necessary to correct any losses of material resulted in considerable variability. In terms of overall uncertainty, it would be better in this case not to carry out correction and to employ an operating mode favouring the recovery of a maximum of material while accepting a bias of about 5–7%.
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Comparison of Direct (X-Ray Diffraction and Infrared Spectrophotometry) and Indirect (Infrared Spectrophotometry) Methods for the Analysis of α-Quartz in Airborne Dusts
The Annals of occupational hygiene, 2005Co-Authors: E. Kauffer, A. Masson, Jean-claude Moulut, T. Lecaque, J. C. ProtoisAbstract:In this study, the a-quartz contents measured by different analytical techniques (X-ray diffraction, direct method; and Infrared Spectrophotometry, direct and indirect methods) were compared. The analyses were carried out on filters sampled in an industrial setting by means of a Dorr-Oliver cyclone. To verify the methodology used, filters loaded with pure a-quartz were also analysed. By and large, the agreement between the two direct methods was close on average, but on the basis of a comparison of the individual results, considerable differences exist. In absolute value, the mean relative deviation between the two techniques was
Hans Ulrich Bucher - One of the best experts on this subject based on the ideXlab platform.
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Novel Multichannel Near Infrared Spectrophotometry System: Functional Studies of the Visual Cortex in Neonates
Biomedical Optics, 2006Co-Authors: G. Morren, Daniel Haensse, Tanja Karen, A. Bauschatz, Derek W. Brown, Hans Ulrich Bucher, M. WolfAbstract:Using a novel non-invasive near-Infrared Spectrophotometry imaging instrument, we measured the changes in cerebral oxy- and deoxyhemoglobin concentration in response to visual stimulation in 15 healthy term neonates.
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A new multichannel near Infrared Spectrophotometry system for functional studies of the brain in adults and neonates.
Optics express, 2005Co-Authors: Daniel Haensse, Derek W. Brown, Hans Ulrich Bucher, Peter Szabo, Jean-claude Fauchère, Peter Niederer, Martin WolfAbstract:We have designed a versatile, multi-channel near-Infrared Spectrophotometry (NIRS) instrument for the purpose of mapping neuronal activation in the neonatal and adult brain in response to motor, tactile, and visual stimulation. The optical linearity, stability, and high signal to noise ratio (>70 dB) of the instrument were demonstrated using an in vitro validation procedure. In vivo measurements on the adult forearm were also performed. Changes in oxygenation, induced by arterial occlusion of the forearm, were recorded and were shown to compare well with measurements acquired using a conventional NIRS instrument. To demonstrate the capabilities of the instrument, functional measurements in adults and neonates were performed. The instrument exhibited the capability to differentiate with a spatial resolution in the order of cm, local activation patterns associated with a finger tapping sequence.
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Regional differences of cerebral hemoglobin concentration in preterm infants measured by near Infrared Spectrophotometry.
Technology and health care : official journal of the European Society for Engineering and Medicine, 1999Co-Authors: M. Keel, Vera Dietz, Martin Wolf, Kurt Von Siebenthal, Oskar Baenziger, Hans Ulrich BucherAbstract:Near Infrared Spectrophotometry has been used to measure total cerebral hemoglobin concentration (micromol/l) as a major indicator of the oxygen transport capacity in neonates. The aim of this study was to find out how the position of the probe influences the quality of the measurement and the actual cerebral hemoglobin concentration-values. We studied 10 healthy preterm infants with a mean gestational age of 31.5 weeks and a birthweight of 1513 g. The data were collected by a two channel near Infrared Spectrophotometry system using a geometrical principle to measure absolute cerebral hemoglobin concentration. The incoming signal of the light emitting diode as a value allows a prediction of the quality of the measurement: a high value refers to a high signal/noise ratio. Starting from the centre of the forehead (0%) for each measurement the probe was moved by 2.5% of the headcircumference to the left respectively right side of the head up to 20%. The cerebral hemoglobin concentration-values increased from 87 respectively 93 micromol/l up to 164 respectively 173 micromol/l on the right respectively left side, while the light emitting diode signal-values decreased from 21 respectively 21 down to 10 respectively 11, the more laterally the probe was moved. There were two plateaus of these variables in the frontal (0-5%) respectively lateral (15-20%) region. A further investigation on a solid phantom for premature heads showed that hair has either no or a contrary effect on the cerebral hemoglobin concentration-values than expected. The extracerebral tissue (soft tissue, skull, cerebrospinal fluid layer) is discussed to have a significant influence on the light attenuation in adult heads. Still there is no evidence for a significant effect on prematures, because this overlying tissue is much thinner and more translucent than the one in adults. Absolute cerebral hemoglobin concentration measured by near Infrared Spectrophotometry is substantially influenced by the position of the probe at the infant's head. Considering our results we recommend placing the probe at 2.5% of the headcircumference away from the centre of the forehead for the measurement of cerebral hemoglobin concentration in premature infants.
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CO2 Reactivity of the Cerebral Hemoglobin Concentration in Healthy Term Newborns Measured by Near Infrared Spectrophotometry
Biology of the neonate, 1998Co-Authors: Vera Dietz, Martin Wolf, M. Keel, Kurt Von Siebenthal, Oskar Baenziger, Hans Ulrich BucherAbstract:CO2 reactivity of cerebral hemoglobin concentration was studied in 16 healthy term neonates on days 1 and 4 after birth using the near Infrared Spectrophotometry (NIRS) technique. The aim w
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Comparison of Absolute Cerebral Haemoglobin Concentration in Neonates Measured Directly and by the Oxygen Swing Method both Based on Near Infrared Spectrophotometry
Advances in experimental medicine and biology, 1998Co-Authors: M. Wolf, Vera Dietz, M. Keel, Oskar Baenziger, Ursula Wolf, K. Von Siebenthal, D. Schenk, Hans Ulrich BucherAbstract:The total cerebral haemoglobin concentration (tHb in μmol/1) as a major indicator of the oxygen transport capacity is investigated in neonates. Two methods to determine tHb by near Infrared Spectrophotometry (NIRS) have evolved so far: The first method requires a slow oxygenation change with reference to arterial oxygen saturation (tHbo-method). The second method is based on a geometrical principle and a two channel NIRS instrument (tHbg-method). The aim of this study was to compare both methods quantitatively.
Don S. Shaw - One of the best experts on this subject based on the ideXlab platform.
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a comparison of international silica α quartz calibration standards by fourier transform Infrared Spectrophotometry
Annals of Occupational Hygiene, 2001Co-Authors: Dave K. Verma, Don S. ShawAbstract:Seven international silica (alpha-quartz) standards were examined for relative purity to the US National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1878 Respirable alpha-quartz by Fourier Transform-Infrared Spectrophotometry (FT-IR). The standards examined have been used in North America, the UK, Australia and Germany. The 189 samples analyzed included NIST-SRM 1878, Min-U-Sil 5, Ottawa Silica Sand, Sikron F-600, A9950 (AUST 1), DQ12-Robock, DQ12-Bergbau. Size distributions of the standards were determined by Coulter Counter to be broadly similar with equivalent spherical volume median diameter ranging between 1.2 and 3 microm. The results showed the standards to differ by as much as 30% in relative purity. Consequently, an internationally agreed upon calibration standard is urgently needed. Min-U-Sil 5 based NIST-SRM 1878 or Sikron F-600 are the two most likely candidates. Any agreed standard must have a well characterized size distribution and closely match the respirable dust criteria. It should also be studied by both Infrared Spectrophotometry and X-ray diffraction techniques.
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A comparison of international silica (α-quartz) calibration standards by Fourier transform–Infrared Spectrophotometry
The Annals of occupational hygiene, 2001Co-Authors: Dave K. Verma, Don S. ShawAbstract:Seven international silica (alpha-quartz) standards were examined for relative purity to the US National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1878 Respirable alpha-quartz by Fourier Transform-Infrared Spectrophotometry (FT-IR). The standards examined have been used in North America, the UK, Australia and Germany. The 189 samples analyzed included NIST-SRM 1878, Min-U-Sil 5, Ottawa Silica Sand, Sikron F-600, A9950 (AUST 1), DQ12-Robock, DQ12-Bergbau. Size distributions of the standards were determined by Coulter Counter to be broadly similar with equivalent spherical volume median diameter ranging between 1.2 and 3 microm. The results showed the standards to differ by as much as 30% in relative purity. Consequently, an internationally agreed upon calibration standard is urgently needed. Min-U-Sil 5 based NIST-SRM 1878 or Sikron F-600 are the two most likely candidates. Any agreed standard must have a well characterized size distribution and closely match the respirable dust criteria. It should also be studied by both Infrared Spectrophotometry and X-ray diffraction techniques.