Universal serial bus powered and controlled isolated constant-current physiological stimulator.
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ABSTRACT:
SUBMITTER: Holcomb MR
PROVIDER: S-EPMC2736648 | biostudies-other | 2008 Dec
REPOSITORIES: biostudies-other
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Project description:We have developed an isolated continuous-waveform constant-current physiological stimulator that is powered and controlled by universal serial bus (USB) interface. The stimulator is composed of a custom printed circuit board (PCB), 16-MHz MSP430F2618 microcontroller with two integrated 12-bit digital to analog converters (DAC0, DAC1), high-speed H-Bridge, voltage-controlled current source (VCCS), isolated USB communication and power circuitry, two isolated transistor-transistor logic (TTL) inputs, and a serial 16 × 2 character liquid crystal display. The stimulators are designed to produce current stimuli in the range of ±15 mA indefinitely using a 20V source and to be used in ex vivo cardiac experiments, but they are suitable for use in a wide variety of research or student experiments that require precision control of continuous waveforms or synchronization with external events. The device was designed with customization in mind and has features that allow it to be integrated into current and future experimental setups. Dual TTL inputs allow replacement by two or more traditional stimulators in common experimental configurations. The MSP430 software is written in C++ and compiled with IAR Embedded Workbench 5.20.2. A control program written in C++ runs on a Windows personal computer and has a graphical user interface that allows the user to control all aspects of the device.
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Project description:The golden ratio, ? = 1.61803…, has often been found in connection with biological phenomena, ranging from spirals in sunflowers to gene frequency. One example where the golden ratio often arises is in self-replication, having its mathematical origins in Fibonacci's sequence for "rabbit reproduction". Recently, it has been claimed that ? determines the ratio between the number of different nucleobases in human genome. Such empirical examples continue to give credence to the idea that the golden ratio is a universal constant, not only in mathematics but also for biology. In this paper, we employ a general framework for chemically realistic self-replicating reaction systems and investigate whether the ratio of chemical species population follows "universal constants". We find that many self-replicating systems can be characterised by an algebraic number, which, in some cases, is the golden ratio. However, many other algebraic numbers arise from these systems, and some of them-such as [Formula: see text] and 1.22074… which is also known as the 3rd lower golden ratio-arise more frequently in self-replicating systems than the golden ratio. The "universal constants" in these systems arise as roots of a limited number of distinct characteristic equations. In addition, these "universal constants" are transient behaviours of self-replicating systems, corresponding to the scenario that the resource inside the system is infinite, which is not always the case in practice. Therefore, we argue that the golden ratio should not be considered as a special universal constant in self-replicating systems, and that the ratios between different chemical species only go to certain numbers under some idealised scenarios.
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Project description:Introduction: Variable power output (VP) is one of the main characteristics of a road cycling mass-start. Tolerating VP during outdoor road cycling highly influences performance. There is a lack of continuous and comprehensive measurements during this power condition. Accordingly, the aim of the present study was to investigate physiological response to VP vs. constant power output (CP) as well as the perceived exertion of these two power conditions, and to investigate if variations in power output which span above lactate threshold (LT), differ from variations below LT. Methods: 15 elite competitive cyclists completed three test days, including 1 day of baseline testing and 2 days of main testing, consisting of four bouts of 28 min at two different intensities, "low" at 70% of LT and "high" at 95% of LT, with VP and CP. VP was performed with a 15% fluctuation of the average power output every second minute. Maximal oxygen uptake (VO2), respiratory exchange ratio (RER), heart rate (HR), blood lactate (LA), rating of perceived exertion (RPE), cadence (RPM) and power output (W) were measured. Results: At both low and high intensity, the VP condition induced a significantly higher VO2, HR and LA than the CP condition. Whole-bout RPE was similar between power conditions at high intensity. Additionally, at the high intensity, cycling with VP led to a greater increase in LA and lesser increase in RPE compared to cycling with CP. Discussion: The results of this study show that, despite considerable differences in the demand during the VP and CP bouts, there are minor differences in the perceptual and physiological response directly following these two power conditions in a cohort of elite competitive cyclists. A practical implication of these findings is that training with VP seems to be a viable alternative to training with CP, at least at high intensity.
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Project description:Self-propelled bacteria can be integrated into synthetic micromachines and act as biological propellers. So far, proposed designs suffer from low reproducibility, large noise levels or lack of tunability. Here we demonstrate that fast, reliable and tunable bio-hybrid micromotors can be obtained by the self-assembly of synthetic structures with genetically engineered biological propellers. The synthetic components consist of 3D interconnected structures having a rotating unit that can capture individual bacteria into an array of microchambers so that cells contribute maximally to the applied torque. Bacterial cells are smooth swimmers expressing a light-driven proton pump that allows to optically control their swimming speed. Using a spatial light modulator, we can address individual motors with tunable light intensities allowing the dynamic control of their rotational speeds. Applying a real-time feedback control loop, we can also command a set of micromotors to rotate in unison with a prescribed angular speed.
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Project description:BACKGROUND:Functional electrical stimulation (FES) is used to restore movements in paretic limbs after severe paralyses resulting from neurological injuries such as spinal cord injury (SCI). Most chronic FES systems utilize an implantable electrical stimulator to deliver a small electric current to the targeted muscle or nerve to stimulate muscle contractions. These implanted stimulators are generally bulky, mainly due to the size of the batteries. Furthermore, these battery-powered stimulators are required to be explanted every few years for battery replacement which may result in surgical failures or infections. Hence, a wireless power transfer technique is desirable to power these implantable stimulators. METHODS:Conventional wireless power transduction faces significant challenges for safe and efficient energy transfer through the skin and deep into the body. Inductive and electromagnetic power transduction is generally used for very short distances and may also interfere with other medical measurements such as X-ray and MRI. To address these issues, we have developed a wireless, ultrasonically powered, implantable piezoelectric stimulator. The stimulator is encapsulated with biocompatible materials. RESULTS:The stimulator is capable of harvesting a maximum of 5.95 mW electric power at an 8-mm depth under the skin from an ultrasound beam with about 380 mW/cm2 of acoustic intensity. The stimulator was implanted in several paraplegic rats with SCI. Our implanted stimulator successfully induced several hindlimb muscle contractions and restored leg movement. CONCLUSIONS:A battery-free miniature (10 mm diameter × 4 mm thickness) implantable stimulator, developed in the current study is capable of directly stimulating paretic muscles through external ultrasound signals. The required cost to develop the stimulator is relatively low as all the components are off the shelf.
| S-EPMC6408863 | biostudies-other