Dynamic Light Scattering: A New Noninvasive Technology for Neonatal Heart Rate Monitoring

Background: Heart rate (HR) detection in premature infants using electrocardiography (ECG) is challenging due to a low signal amplitude and the fragility of the premature skin. Recently, the dynamic light scattering (DLS) technique has been miniaturized, allowing noninvasive HR measurements with a single sensor. Objective: The aim was to determine the accuracy of DLS for HR measurement in infants, compared to ECG-derived HR. Methods: Stable infants with a gestational age of ≥26 weeks, monitored with ECG, were eligible for inclusion. HR was measured with the DLS sensor at 5 different sites for 15 min each. We recorded every 10th second of the DLS-derived HR and the DLS signal-to-noise ratio (SNR), and the ECG-derived HR was extracted for analysis. Patients were randomly divided into 2 groups. In the first group, the optimal SNR cut-off value was determined and then applied to the second group to assess agreement. Results: HR measurements from 31 infants were analyzed. ECG-DLS paired data points were collected at the forehead, an upper extremity, the thorax, a lower extremity, and the abdomen. When applying the international accuracy standard for HR detection, DLS accuracy in the first group (n = 15) was optimal at the forehead (SNR cut-off 1.66). Application of this cut-off to the second group (n = 16) showed good agreement between DLS-derived HR and ECG-derived HR (bias –0.73 bpm; 95% limits of agreement –15.46 and 14.00 bpm) at the forehead with approximately 80% (i.e., 1,066/1,310) of all data pairs remaining. Conclusion: The investigated DLS sensor was sensitive to movement, overall providing less accurate HR measurements than ECG and pulse oximetry. In this study population, specific measurement sites provided excellent signal quality and good agreement with ECG-derived HR

Dynamic Light Scattering: A New Noninvasive Technology for Neonatal Heart Rate Monitoring

Background: Heart rate (HR) detection in premature infants using electrocardiography (ECG) is challenging due to a low signal amplitude and the fragility of the premature skin. Recently, the dynamic light scattering (DLS) technique has been miniaturized, allowing noninvasive HR measurements with a single sensor. Objective: The aim was to determine the accuracy of DLS for HR measurement in infants, compared to ECG-derived HR. Methods: Stable infants with a gestational age of ≥26 weeks, monitored with ECG, were eligible for inclusion. HR was measured with the DLS sensor at 5 different sites for 15 min each. We recorded every 10th second of the DLS-derived HR and the DLS signal-to-noise ratio (SNR), and the ECG-derived HR was extracted for analysis. Patients were randomly divided into 2 groups. In the first group, the optimal SNR cut-off value was determined and then applied to the second group to assess agreement. Results: HR measurements from 31 infants were analyzed. ECG-DLS paired data points were collected at the forehead, an upper extremity, the thorax, a lower extremity, and the abdomen. When applying the international accuracy standard for HR detection, DLS accuracy in the first group (n = 15) was optimal at the forehead (SNR cut-off 1.66). Application of this cut-off to the second group (n = 16) showed good agreement between DLS-derived HR and ECG-derived HR (bias -0.73 bpm; 95% limits of agreement -15.46 and 14.00 bpm) at the forehead with approximately 80% (i.e., 1,066/1,310) of all data pairs remaining. Conclusion: The investigated DLS sensor was sensitive to movement, overall providing less accurate HR measurements than ECG and pulse oximetry. In this study population, specific measurement sites provided excellent signal quality and good agreement with ECG-derived HR

Albumin-Associated Lipids Regulate Human Embryonic Stem Cell Self-Renewal

BACKGROUND: Although human embryonic stem cells (hESCs) hold great promise as a source of differentiated cells to treat several human diseases, many obstacles still need to be surmounted before this can become a reality. First among these, a robust chemically-defined system to expand hESCs in culture is still unavailable despite recent advances in the understanding of factors controlling hESC self-renewal. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we attempted to find new molecules that stimulate long term hESC self-renewal. In order to do this, we started from the observation that a commercially available serum replacement product has a strong positive effect on the expansion of undifferentiated hESCs when added to a previously reported chemically-defined medium. Subsequent experiments demonstrated that the active ingredient within the serum replacement is lipid-rich albumin. Furthermore, we show that this activity is trypsin-resistant, strongly suggesting that lipids and not albumin are responsible for the effect. Consistent with this, lipid-poor albumin shows no detectable activity. Finally, we identified the major lipids bound to the lipid-rich albumin and tested several lipid candidates for the effect. CONCLUSIONS/SIGNIFICANCE: Our discovery of the role played by albumin-associated lipids in stimulating hESC self-renewal constitutes a significant advance in the knowledge of how hESC pluripotency is maintained by extracellular factors and has important applications in the development of increasingly chemically defined hESC culture systems

Dealing with clay when mining diamonds offshore: High rate mining tool development

De Beers Marine is currently mining diamonds offshore near the Namibian coast (at water depths of 115 - 140 meters), using a vertical batch drill mining system ('Wirth drill"). Previously also continuous seabed crawlers have been used, but this method was discontinued because of unsatisfactory operational performance and recovery of the diamonds. New crawler-type mining tools (latest tool is the so-called "Gravel Wheel") are being developed due to their higher mining rate potential compared to the Wirth drill. On 1/3 scale different versions of the Gravel Wheel had been thoroughly tested on imitated seabeds of gravel and initial tests had been done in clay. Since together with the gravel on average 5 to 10 cm (up to 30 cm) of underlying clay footwall may have to be loosened and removed more thorough tests have to be done in clay. The first reason to study the cutting into clay is the irregular gravel-footwall interface, which makes it nearly impossible to stay right at this interface all the time. Secondly, 100% of the diamonds have to be removed since the likelihood of diamonds occurring at the gravel-footwall interface is high. With the Gravel Wheel currently being tested, the focus of this study is to mine both gravel and clay with one tool in one step. The main objective of this study is to define and improve the clay handling ability of the current Gravel Wheel model MkIII through scaled testing. The clay handling ability is specified as the ability to remain 100% clear from blockages and the ability to penetrate the clay footwall for 50 mm (full scale) whilst mining gravel. To reach to goals set, sub-objectives set are to establish a proper theoretical basis for the execution of scaled tests in clay, as well as derive basic design guidelines from experience in other related industries in order to evaluate and improve the Gravel Wheels' clay handling ability. In the attempt to achieve similarity between model and full scale, three scenarios for scaled testing are identified. Although all three show scale effects, the most favourable scenario is selected to perform scaled tests. The main drawback of this scenario is that the clays' shear strength is not scaled back correctly in ratio to the force to mould the cut clay lumps (drag force). The consequence is that the test conditions on model scale are much tougher than on full scale. It is argued that if this scenario is used in scaled testing and if testing is successful, the tool will definitely work on full scale. From experience in dredging several design guidelines have been derived to evaluate a tools' clay cutting ability and an initial evaluation of the Gravel Wheel has been made. The Gravel Wheel scores negative on the risk of bulldozing, openness of the tool and the converging shape of the suction duct and these features are expected to be most critical in the Gravel Wheels' design. Based on this analysis the scoop grizzly has been modified to reduce the risk of bulldozing. The scaled tests (continued on 1/3 scale) prove that the maximum cut depth at which the tool remains free from blockage increases with increased rotational speed and modified scoop design. On model scale a 100 mm cut in clay has been achieved with a rotational speed of 20 RPM and a modified scoop design. Tests show that while mining gravel, a 20 mm and 50 mm cut in clay can be achieved at forward mining speeds of 2.5 and 1.7 m/min respectively. Further modifications to the scoop are made to reduce the obstructing side effect of the grizzly bars. The test results confirm that the risk of bulldozing and the converging shape of the suction duct are the most critical features in the Gravel Wheels design. The obstructing side effect of the grizzly bars has also been recognized as problematic. It is recommended that more shear strength testing is done on offshore footwall clays to get more insight in the actual clay footwall shear strengths since currently only limited shear strength data of the clay footwall is available. Further more tests in clay and gravel should be performed to find the optimum operational parameters (e.g. forward mining speed) at different set cut depths: initial tests in clay and gravel have proven valuable to study the clay and gravel interaction and initial trends have been observed. The necessity to achieve a specific cut depth in clay depends all on the degree of undulation and the accuracy with which the clay-gravel interface can be followed. It is therefore finally recommended to further study these factors in order to better define the clay cut depth requirement of any mining tool.Applied GeologyGeoscience & EngineeringCivil Engineering and Geoscience

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