Background:The benefits associated with sports compression garments are thought to be closely related to enhanced blood flow.However,findings are equivocal,possibly due to heterogeneity in the techniques used for meas...Background:The benefits associated with sports compression garments are thought to be closely related to enhanced blood flow.However,findings are equivocal,possibly due to heterogeneity in the techniques used for measuring blood flow,the garment types used,and the pressures applied.This study combined Doppler ultrasound and near-infrared spectroscopy technologies to provide the first comprehensive assessment of the effects of 3 sports compression garment types on markers of venous return and muscle blood flow at rest.Methods:Resting lower-limb blood flow measures(markers of venous return,muscle blood flow,and muscle oxygenation)of 22 elite,junior,male basketball players(age=17.2±0.9 years,mean±SD)were assessed in 4 separate conditions:no compression(CON),compression tights(TIGHTS),compression shorts(SHORTS),and compression socks(SOCKS).Markers of venous return(cross-sectional area,time-averaged mean and peak blood flow velocity,and venous blood flow)were measured via Doppler ultrasound at the popliteal and common femoral veins.Muscle blood flow and muscle oxygenation were measured in the gastrocnemius medialis and vastus lateralis using near-infrared spectroscopy.Results:Popliteal markers of venous return were higher in TIGHTS compared to CON(p<0.01)and SHORTS(p<0.01),with SOCKS values higher compared with CON(p<0.05).Common femoral vein markers of venous return were higher for all conditions compared to CON(p<0.05),with TIGHTS values also higher compared to SOCKS(p<0.05).Gastrocnemius medialis blood flow was higher for TIGHTS compared to CON(p=0.000),SOCKS(p=0.012),and SHORTS(p=0.000),with SOCKS higher compared to SHORTS(p=0.046).Vastus lateralis blood flow was higher for TIGHTS compared to CON(p=0.028)and SOCKS(p=0.019),with SHORTS also higher compared to CON(p=0.012)and SOCKS(p=0.005).Gastrocnemius medialis oxygenation was higher for TIGHTS compared to CON(p=0.003),SOCKS(p=0.033),and SHORTS(p=0.003),with SOCKS higher compared to CON(p=0.044)and SHORTS(p=0.032).Vastus lateralis oxygenation was higher for TIGH展开更多
Purpose:This article identifies an issue in mathematics education,that is,the perceived lack of emphasis in recent times of the roles that the"person"plays in the development of mathematics.The purpose is to...Purpose:This article identifies an issue in mathematics education,that is,the perceived lack of emphasis in recent times of the roles that the"person"plays in the development of mathematics.The purpose is to exami ne how values/valui ng might con tribute to addressi ng the issue.Design/Approach/Methods:“Data”were collected from several purposeful conversations among the three authors.The conversations were audio-recorded and machine-transcribed.The transcript was then subjected to content analysis to identify themes.Findings:The data analysis yielded two novel approaches to raising learners'awareness of the humanness of mathematics.One would be to reframe the values that are operationalized when mathematics is taught and learnt,as processes of valuing which teachers and students engage in,respectively.The sec ond approach would be to ack no wledge that writers of mathematics/mathematicia ns are not simply prese nting kn owledge but are also acti ng as men tors conv eying and transmitting messages about the discipline.Originality/Value:The invoIvement of the"person" in the development of mathematics is not new knowledge,though it can be made more visible in mathematics education.This article identifies two approaches-valuing and mentoring-which are novel in that they are already part of the pedagogical process and thus,accessible.展开更多
Nuclear nonproliferation is of critical importance for global security.Dangerous fissile materials including highly enriched uranium and weapons-grade plutonium are especially important to detect.Active interrogation ...Nuclear nonproliferation is of critical importance for global security.Dangerous fissile materials including highly enriched uranium and weapons-grade plutonium are especially important to detect.Active interrogation techniques may result in much better sensitivity but are difficult with conventional portal monitors that rely on detecting thermal neutrons.Also,most conventional portal monitoring systems rely on ^(3)He,which has a finite and continually decreasing supply.By designing a highly segmented array of organic scintillators,we posit that we can accurately and quickly identify fissile materials,including weapons-grade plutonium and highly enriched uranium,being smuggled.We propose a new design for a fast-neutron detector that overcomes the limitations of the current generation of portal monitors.MCNP6 simulations have been performed in conjunction with the UMPBT statistical model to determine the sensitivity limitations of the proposed detector.Results suggest that the proposed detector may be 10 times more efficient than current-generation thermal neutron detectors and may be able to positively identify a 81 mg 235U source in as little as 192 seconds utilizing active interrogation techniques.展开更多
In this paper,we summarise the outcome of a set of experiments aimed at classifying cattle behaviour based on sensor data.Each animal carried sensors generating time series accelerometer data placed on a collar on the...In this paper,we summarise the outcome of a set of experiments aimed at classifying cattle behaviour based on sensor data.Each animal carried sensors generating time series accelerometer data placed on a collar on the neck at the back of the head,on a halter positioned at the side of the head behind the mouth,or on the ear using a tag.The purpose of the study was to determine how sensor data from different placement can classify a range of typical cattle behaviours.Data were collected and animal behaviours(grazing,standing or ruminating)were observed over a common time frame.Statistical features were computed from the sensor data and machine learning algorithms were trained to classify each behaviour.Classification accuracies were computed on separate independent test sets.The analysis based on behaviour classification experiments revealed that different sensor placement can achieve good classification accuracy if the feature space(representing motion patterns)between the training and test animal is similar.The paper will discuss these analyses in detail and can act as a guide for future studies.展开更多
Magnetic sensing is present in our everyday interactions with consumer electronics and demonstrates the potential for the measurement of extremely weak biomagnetic fields,such as those of the heart and brain.In this w...Magnetic sensing is present in our everyday interactions with consumer electronics and demonstrates the potential for the measurement of extremely weak biomagnetic fields,such as those of the heart and brain.In this work,we leverage the many benefits of microelectromechanical system(MEMS)devices to fabricate a small,low-power,and inexpensive sensor whose resolution is in the range of biomagnetic fields.At present,biomagnetic fields are measured only by expensive mechanisms such as optical pumping and superconducting quantum interference devices(SQUIDs),suggesting a large opportunity for MEMS technology in this work.The prototype fabrication is achieved by assembling micro-objects,including a permanent micromagnet,onto a postrelease commercial MEMS accelerometer using a pick-and-place technique.With this system,we demonstrate a room-temperature MEMS magnetic gradiometer.In air,the sensor’s response is linear,with a resolution of 1.1 nT cm^(−1),spans over 3 decades of dynamic range to 4.6µT cm^(−1),and is capable of off-resonance measurements at low frequencies.In a 1mTorr vacuum with 20 dB magnetic shielding,the sensor achieves a 100 pT cm^(−1) resolution at resonance.This resolution represents a 30-fold improvement compared with that of MEMS magnetometer technology and a 1000-fold improvement compared with that of MEMS gradiometer technology.The sensor is capable of a small spatial resolution with a magnetic sensing element of 0.25 mm along its sensitive axis,a>4-fold improvement compared with that of MEMS gradiometer technology.The calculated noise floor of this platform is 110 fTcm^(−1) Hz−1/2,and thus,these devices hold promise for both magnetocardiography(MCG)and magnetoencephalography(MEG)applications.展开更多
In this article,we present a nanoelectromechanical system(NEMS)designed to detect changes in the Casimir energy.The Casimir effect is a result of the appearance of quantum fluctuations in an electromagnetic vacuum.Pre...In this article,we present a nanoelectromechanical system(NEMS)designed to detect changes in the Casimir energy.The Casimir effect is a result of the appearance of quantum fluctuations in an electromagnetic vacuum.Previous experiments have used nano-or microscale parallel plate capacitors to detect the Casimir force by measuring the small attractive force these fluctuations exert between the two surfaces.In this new set of experiments,we aim to directly detect the shifts in the Casimir energy in a vacuum due to the presence of the metallic parallel plates,one of which is a superconductor.A change in the Casimir energy of this configuration is predicted to shift the superconducting transition temperature(T_(c))because of the interaction between it and the superconducting condensation energy.In our experiment,we take a superconducting film,carefully measure its transition temperature,bring a conducting plate close to the film,create a Casimir cavity,and then measure the transition temperature again.The expected shifts are smaller than the normal shifts one sees in cycling superconducting films to cryogenic temperatures,so using a NEMS resonator in situ is the only practical way to obtain accurate,reproducible data.Using a thin Pb film and opposing Au surface,we observe no shift in T_(c)>12µK down to a minimum spacing of~70 nm at zero applied magnetic field.展开更多
The structural and functional maturation of human induced pluripotent stem cell-derived cardiomyocytes(hiPSC-CMs)is essential for pharmaceutical testing,disease modeling,and ultimately therapeutic use.Multicellular 3D...The structural and functional maturation of human induced pluripotent stem cell-derived cardiomyocytes(hiPSC-CMs)is essential for pharmaceutical testing,disease modeling,and ultimately therapeutic use.Multicellular 3D-tissue platforms have improved the functional maturation of hiPSC-CMs,but probing cardiac contractile properties in a 3D environment remains challenging,especially at depth and in live tissues.Using small-angle X-ray scattering(SAXS)imaging,we show that hiPSC-CMs matured and examined in a 3D environment exhibit a periodic spatial arrangement of the myofilament lattice,which has not been previously detected in hiPSC-CMs.The contractile force is found to correlate with both the scattering intensity(R^(2)=0.44)and lattice spacing(R^(2)=0.46).The scattering intensity also correlates with lattice spacing(R^(2)=0.81),suggestive of lower noise in our structural measurement than in the functional measurement.Notably,we observed decreased myofilament ordering in tissues with a myofilament mutation known to lead to hypertrophic cardiomyopathy(HCM).Our results highlight the progress of human cardiac tissue engineering and enable unprecedented study of structural maturation in hiPSC-CMs.展开更多
The Casimir force,a quantum mechanical effect,has been observed in several microelectromechanical system(MEMS)platforms.Due to its extreme sensitivity to the separation of two objects,the Casimir force has been propos...The Casimir force,a quantum mechanical effect,has been observed in several microelectromechanical system(MEMS)platforms.Due to its extreme sensitivity to the separation of two objects,the Casimir force has been proposed as an excellent avenue for quantum metrology.Practical application,however,is challenging due to attractive forces leading to stiction and device failure,called Casimir pull-in.In this work,we design and simulate a Casimir-driven metrology platform,where a time-delay-based parametric amplification technique is developed to achieve a steady-state and avoid pull-in.We apply the design to the detection of weak,low-frequency,gradient magnetic fields similar to those emanating from ionic currents in the heart and brain.Simulation parameters are selected from recent experimental platforms developed for Casimir metrology and magnetic gradiometry,both on MEMS platforms.While a MEMS offers many advantages to such an application,the detected signal must typically be at the resonant frequency of the device,with diminished sensitivity in the low frequency regime of biomagnetic fields.Using a Casimir-driven parametric amplifier,we report a 10,000-fold improvement in the best-case resolution of MEMS single-point gradiometers,with a maximum sensitivity of 6 Hz/(pT/cm)at 1 Hz.Further development of the proposed design has the potential to revolutionize metrology and may specifically enable the unshielded monitoring of biomagnetic fields in ambient conditions.展开更多
文摘Background:The benefits associated with sports compression garments are thought to be closely related to enhanced blood flow.However,findings are equivocal,possibly due to heterogeneity in the techniques used for measuring blood flow,the garment types used,and the pressures applied.This study combined Doppler ultrasound and near-infrared spectroscopy technologies to provide the first comprehensive assessment of the effects of 3 sports compression garment types on markers of venous return and muscle blood flow at rest.Methods:Resting lower-limb blood flow measures(markers of venous return,muscle blood flow,and muscle oxygenation)of 22 elite,junior,male basketball players(age=17.2±0.9 years,mean±SD)were assessed in 4 separate conditions:no compression(CON),compression tights(TIGHTS),compression shorts(SHORTS),and compression socks(SOCKS).Markers of venous return(cross-sectional area,time-averaged mean and peak blood flow velocity,and venous blood flow)were measured via Doppler ultrasound at the popliteal and common femoral veins.Muscle blood flow and muscle oxygenation were measured in the gastrocnemius medialis and vastus lateralis using near-infrared spectroscopy.Results:Popliteal markers of venous return were higher in TIGHTS compared to CON(p<0.01)and SHORTS(p<0.01),with SOCKS values higher compared with CON(p<0.05).Common femoral vein markers of venous return were higher for all conditions compared to CON(p<0.05),with TIGHTS values also higher compared to SOCKS(p<0.05).Gastrocnemius medialis blood flow was higher for TIGHTS compared to CON(p=0.000),SOCKS(p=0.012),and SHORTS(p=0.000),with SOCKS higher compared to SHORTS(p=0.046).Vastus lateralis blood flow was higher for TIGHTS compared to CON(p=0.028)and SOCKS(p=0.019),with SHORTS also higher compared to CON(p=0.012)and SOCKS(p=0.005).Gastrocnemius medialis oxygenation was higher for TIGHTS compared to CON(p=0.003),SOCKS(p=0.033),and SHORTS(p=0.003),with SOCKS higher compared to CON(p=0.044)and SHORTS(p=0.032).Vastus lateralis oxygenation was higher for TIGH
基金supported by EdUHK Dean s Research Fund(Ref.:DRF/1RS-7/18-19)FLASS Internationalization and Exchange Scheme(Ref.:FLASS/IE D03/18-19).
文摘Purpose:This article identifies an issue in mathematics education,that is,the perceived lack of emphasis in recent times of the roles that the"person"plays in the development of mathematics.The purpose is to exami ne how values/valui ng might con tribute to addressi ng the issue.Design/Approach/Methods:“Data”were collected from several purposeful conversations among the three authors.The conversations were audio-recorded and machine-transcribed.The transcript was then subjected to content analysis to identify themes.Findings:The data analysis yielded two novel approaches to raising learners'awareness of the humanness of mathematics.One would be to reframe the values that are operationalized when mathematics is taught and learnt,as processes of valuing which teachers and students engage in,respectively.The sec ond approach would be to ack no wledge that writers of mathematics/mathematicia ns are not simply prese nting kn owledge but are also acti ng as men tors conv eying and transmitting messages about the discipline.Originality/Value:The invoIvement of the"person" in the development of mathematics is not new knowledge,though it can be made more visible in mathematics education.This article identifies two approaches-valuing and mentoring-which are novel in that they are already part of the pedagogical process and thus,accessible.
基金supported by the National Nuclear Security Administration(NNSA)through the Center for Excellence in Nuclear Training and University Based Research(CENTAUR)under Award No.DE-NA0003841by the U.S.Department of Energy,Office of Science,Office of Nuclear Physics,under Award No.DE-FG02-93ER40773the College of Science at Texas A&M University through Strategic Transformative Research Program(CoS STRP).
文摘Nuclear nonproliferation is of critical importance for global security.Dangerous fissile materials including highly enriched uranium and weapons-grade plutonium are especially important to detect.Active interrogation techniques may result in much better sensitivity but are difficult with conventional portal monitors that rely on detecting thermal neutrons.Also,most conventional portal monitoring systems rely on ^(3)He,which has a finite and continually decreasing supply.By designing a highly segmented array of organic scintillators,we posit that we can accurately and quickly identify fissile materials,including weapons-grade plutonium and highly enriched uranium,being smuggled.We propose a new design for a fast-neutron detector that overcomes the limitations of the current generation of portal monitors.MCNP6 simulations have been performed in conjunction with the UMPBT statistical model to determine the sensitivity limitations of the proposed detector.Results suggest that the proposed detector may be 10 times more efficient than current-generation thermal neutron detectors and may be able to positively identify a 81 mg 235U source in as little as 192 seconds utilizing active interrogation techniques.
文摘In this paper,we summarise the outcome of a set of experiments aimed at classifying cattle behaviour based on sensor data.Each animal carried sensors generating time series accelerometer data placed on a collar on the neck at the back of the head,on a halter positioned at the side of the head behind the mouth,or on the ear using a tag.The purpose of the study was to determine how sensor data from different placement can classify a range of typical cattle behaviours.Data were collected and animal behaviours(grazing,standing or ruminating)were observed over a common time frame.Statistical features were computed from the sensor data and machine learning algorithms were trained to classify each behaviour.Classification accuracies were computed on separate independent test sets.The analysis based on behaviour classification experiments revealed that different sensor placement can achieve good classification accuracy if the feature space(representing motion patterns)between the training and test animal is similar.The paper will discuss these analyses in detail and can act as a guide for future studies.
基金This work was supported by the NSF CELL-MET ERC award no.1647837 and a SONY Faculty Innovation Award.
文摘Magnetic sensing is present in our everyday interactions with consumer electronics and demonstrates the potential for the measurement of extremely weak biomagnetic fields,such as those of the heart and brain.In this work,we leverage the many benefits of microelectromechanical system(MEMS)devices to fabricate a small,low-power,and inexpensive sensor whose resolution is in the range of biomagnetic fields.At present,biomagnetic fields are measured only by expensive mechanisms such as optical pumping and superconducting quantum interference devices(SQUIDs),suggesting a large opportunity for MEMS technology in this work.The prototype fabrication is achieved by assembling micro-objects,including a permanent micromagnet,onto a postrelease commercial MEMS accelerometer using a pick-and-place technique.With this system,we demonstrate a room-temperature MEMS magnetic gradiometer.In air,the sensor’s response is linear,with a resolution of 1.1 nT cm^(−1),spans over 3 decades of dynamic range to 4.6µT cm^(−1),and is capable of off-resonance measurements at low frequencies.In a 1mTorr vacuum with 20 dB magnetic shielding,the sensor achieves a 100 pT cm^(−1) resolution at resonance.This resolution represents a 30-fold improvement compared with that of MEMS magnetometer technology and a 1000-fold improvement compared with that of MEMS gradiometer technology.The sensor is capable of a small spatial resolution with a magnetic sensing element of 0.25 mm along its sensitive axis,a>4-fold improvement compared with that of MEMS gradiometer technology.The calculated noise floor of this platform is 110 fTcm^(−1) Hz−1/2,and thus,these devices hold promise for both magnetocardiography(MCG)and magnetoencephalography(MEG)applications.
基金This work is supported in part by the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Center for Nanoscale Science and Technology,Award 70NANB10H193,through the University of MarylandAdditional support of this work is provided by the National Science Foundation under Grants EEC-1647837,ECCS-1708283,EEC-0812056,a SONY Faculty Innovation Award,and DARPA/AFRL through award FA8650-15-C-7545。
文摘In this article,we present a nanoelectromechanical system(NEMS)designed to detect changes in the Casimir energy.The Casimir effect is a result of the appearance of quantum fluctuations in an electromagnetic vacuum.Previous experiments have used nano-or microscale parallel plate capacitors to detect the Casimir force by measuring the small attractive force these fluctuations exert between the two surfaces.In this new set of experiments,we aim to directly detect the shifts in the Casimir energy in a vacuum due to the presence of the metallic parallel plates,one of which is a superconductor.A change in the Casimir energy of this configuration is predicted to shift the superconducting transition temperature(T_(c))because of the interaction between it and the superconducting condensation energy.In our experiment,we take a superconducting film,carefully measure its transition temperature,bring a conducting plate close to the film,create a Casimir cavity,and then measure the transition temperature again.The expected shifts are smaller than the normal shifts one sees in cycling superconducting films to cryogenic temperatures,so using a NEMS resonator in situ is the only practical way to obtain accurate,reproducible data.Using a thin Pb film and opposing Au surface,we observe no shift in T_(c)>12µK down to a minimum spacing of~70 nm at zero applied magnetic field.
基金supported by NSF CELL-MET ERC award no.1647837 and NSF GRFP(DGE-1840990,J.K.E.)。
文摘The structural and functional maturation of human induced pluripotent stem cell-derived cardiomyocytes(hiPSC-CMs)is essential for pharmaceutical testing,disease modeling,and ultimately therapeutic use.Multicellular 3D-tissue platforms have improved the functional maturation of hiPSC-CMs,but probing cardiac contractile properties in a 3D environment remains challenging,especially at depth and in live tissues.Using small-angle X-ray scattering(SAXS)imaging,we show that hiPSC-CMs matured and examined in a 3D environment exhibit a periodic spatial arrangement of the myofilament lattice,which has not been previously detected in hiPSC-CMs.The contractile force is found to correlate with both the scattering intensity(R^(2)=0.44)and lattice spacing(R^(2)=0.46).The scattering intensity also correlates with lattice spacing(R^(2)=0.81),suggestive of lower noise in our structural measurement than in the functional measurement.Notably,we observed decreased myofilament ordering in tissues with a myofilament mutation known to lead to hypertrophic cardiomyopathy(HCM).Our results highlight the progress of human cardiac tissue engineering and enable unprecedented study of structural maturation in hiPSC-CMs.
基金the NSF CELL-MET ERC award no.1647837 and a SONY Faculty Innovation Award.
文摘The Casimir force,a quantum mechanical effect,has been observed in several microelectromechanical system(MEMS)platforms.Due to its extreme sensitivity to the separation of two objects,the Casimir force has been proposed as an excellent avenue for quantum metrology.Practical application,however,is challenging due to attractive forces leading to stiction and device failure,called Casimir pull-in.In this work,we design and simulate a Casimir-driven metrology platform,where a time-delay-based parametric amplification technique is developed to achieve a steady-state and avoid pull-in.We apply the design to the detection of weak,low-frequency,gradient magnetic fields similar to those emanating from ionic currents in the heart and brain.Simulation parameters are selected from recent experimental platforms developed for Casimir metrology and magnetic gradiometry,both on MEMS platforms.While a MEMS offers many advantages to such an application,the detected signal must typically be at the resonant frequency of the device,with diminished sensitivity in the low frequency regime of biomagnetic fields.Using a Casimir-driven parametric amplifier,we report a 10,000-fold improvement in the best-case resolution of MEMS single-point gradiometers,with a maximum sensitivity of 6 Hz/(pT/cm)at 1 Hz.Further development of the proposed design has the potential to revolutionize metrology and may specifically enable the unshielded monitoring of biomagnetic fields in ambient conditions.
