Cardiovascular instrumentation

A brief introductory treatment is made of the physiology and instrumentation of the cardiovascular system. Two areas are singled out for further investigation. Arterial blood flow is investigated. In particular the effects of atherosclerosis on the pulse wave propagation through the arterial system are considered. A method for assessing arterial condition employing two ultrasonic Doppler flowmeters is proposed. A digital zero-crossing detection system is suggested as a means of producing a relatively simple and inexpensive instrument to provide real-time results. The performance of the heart as a pump and the parameters used to assess this performance are considered. One such parameter is the cardiac ejection fraction, which relates the stroke and end-diastolic volumes of the heart's left ventricle. A new method of estimating left ventricular volume from single-plane cineangiocardiograms is described. Called the Rectangular Rule, this method approximates the volume to a series of circular discs. A special-purpose calculator has been developed to implement the Rectangular Rule and to make cardiac ejection fraction estimations. Results of studies made of patients indicate that the calculator produces results at least as accurate as those of an other popular method, and that the cardiac ejection fraction is a valuable guide to surgical prognosis

Contributions to electrocardiographic science

This thesis reports original theoretical and experimental studies related to the measurement and interpretation of the electrical activity of the heart. The relevant literature and clinical practice are reviewed at length. Part I is a review of the science of electrocardiography. Included in the review are the electrophysiology of the heart, the potential theory which relates the electrocardiogram (E.C.G.) to its source, the various schemes used to measure and interpret the E.C.G. and the use of computer modelling to aid in E.C.G. interpretation. The effects of body shape and internal conductivity inhomogeneities on the E.C.G. are studied by means of a computer model. A simple form of the model has a piecewise homogeneous interior with spherical boundaries and a surface admittance is invoked to model changes in the surface shape. An extended form of the model allows the boundaries to be irregular and it is solved by means of an integral equation and the extended boundary condition. Representative numerical results are presented, illustrating the practical utility of the model. The sensitivity of the E.C.G. to certain types of inhomogeneity and surface shape changes is established. An experimental study, supported by a computer model based on the techniques outlined above, of the non-invasive detection of the signals from the ventricular specialised conduction system is reported. Thirty-five subjects were studied using a measurement system with a frequency response extending from 0.1 Hz to 500 Hz (-3 dB points) and using a pair of chest electrodes (similar to Lead CM1), Signal averaging was performed on groups of approximately 50 beats, using the onset of the QRS wave as a timing reference. The signals were detected with certainty in 85% of the subjects studied. The typical measured signal waveform is remarkably similar to that predicted by the aforementioned computer modelling technique. Two features are identified: an initial positive deflection (which probably represents the initial activation of the bundle branches) and a notch approximately 10 msec later (which may represent the passage of the activation into the bundle branches)

Protocol for a pragmatic feasibility randomised controlled trial of peer coaching for adults with long-term conditions: PEER CONNECT.

INTRODUCTION: Patients with low levels of knowledge, skills and confidence to manage their health and well-being (activation) are more likely to have unmet health needs, delay seeking healthcare and need emergency care. National Health Service England estimates that this may be applicable to 25%-40% of patients with long-term health conditions. Volunteer peer coaching may support people to increase their level of activation. This form of intervention may be particularly effective for people with low levels of activation. METHODS AND ANALYSIS: This single site, two-arm randomised controlled trial has been designed to assess the feasibility of conducting a definitive trial of volunteer peer health and well-being coaching for people with long-term health conditions (multiple sclerosis, rheumatic diseases or chronic pain) and low activation. Feasibility outcomes include recruitment and retention rates, and intervention adherence. We will measure patient activation, mental health and well-being as potential outcomes for a definitive trial. These outcomes will be summarised descriptively for each time point by allocated group and help to inform sample size calculation for the definitive trial. Criteria for progression to a full trial will be used. ETHICS AND DISSEMINATION: Ethical approval has been granted by the London - Surrey Research Ethics Committee, reference 21/LO/0715. Results from this feasibility trial will be shared directly with participants, presented at local, regional and national conferences and published in an open-access journal. TRIAL REGISTRATION NUMBER: ISRCTN12623577

A study of the dissociative recombination of CaO + with electrons: Implications for Ca chemistry in the upper atmosphere

The dissociative recombination of CaO+ ions with electrons has been studied in a flowing afterglow reactor. CaO+ was generated by the pulsed laser ablation of a Ca target, followed by entrainment in an Ar+ ion/electron plasma. A kinetic model describing the gas-phase chemistry and diffusion to the reactor walls was fitted to the experimental data, yielding a rate coefficient of (3.0 ± 1.0) × 10¯⁷ cm³ molecule¯¹ s¯¹ at 295 K. This result has two atmospheric implications. First, the surprising observation that the Ca+/Fe+ ratio is ~8 times larger than Ca/Fe between 90 and 100 km in the atmosphere can now be explained quantitatively by the known ion-molecule chemistry of these two metals. Second, the rate of neutralization of Ca+ ions in a descending sporadic E layer is fast enough to explain the often explosive growth of sporadic neutral Ca layers

Rapid metabolic profiling of Nicotiana tabacum defence responses against Phytophthora nicotianae using direct infrared laser desorption ionization mass spectrometry and principal component analysis

<p>Abstract</p> <p>Background</p> <p>Successful defence of tobacco plants against attack from the oomycete <it>Phytophthora nicotianae </it>includes a type of local programmed cell death called the hypersensitive response. Complex and not completely understood signaling processes are required to mediate the development of this defence in the infected tissue. Here, we demonstrate that different families of metabolites can be monitored in small pieces of infected, mechanically-stressed, and healthy tobacco leaves using direct infrared laser desorption ionization orthogonal time-of-flight mass spectrometry. The defence response was monitored for 1 - 9 hours post infection.</p> <p>Results</p> <p>Infrared laser desorption ionization orthogonal time-of-flight mass spectrometry allows rapid and simultaneous detection in both negative and positive ion mode of a wide range of naturally occurring primary and secondary metabolites. An unsupervised principal component analysis was employed to identify correlations between changes in metabolite expression (obtained at different times and sample treatment conditions) and the overall defence response.</p> <p>A one-dimensional projection of the principal components 1 and 2 obtained from positive ion mode spectra was used to generate a Biological Response Index (BRI). The BRI obtained for each sample treatment was compared with the number of dead cells found in the respective tissue. The high correlation between these two values suggested that the BRI provides a rapid assessment of the plant response against the pathogen infection. Evaluation of the loading plots of the principal components (1 and 2) reveals a correlation among three metabolic cascades and the defence response generated in infected leaves. Analysis of selected phytohormones by liquid chromatography electrospray ionization mass spectrometry verified our findings.</p> <p>Conclusion</p> <p>The described methodology allows for rapid assessment of infection-specific changes in the plant metabolism, in particular of phenolics, alkaloids, oxylipins, and carbohydrates. Moreover, potential novel biomarkers can be detected and used to predict the quality of plant infections.</p

Past and future trends of Cryptosporidium in vitro research

Cryptosporidium is a genus of single celled parasites capable of infecting a wide range of animals including humans. Cryptosporidium species are members of the phylum apicomplexa, which includes well-known genera such as Plasmodium and Toxoplasma. Cryptosporidium parasites cause a severe gastro-intestinal disease known as cryptosporidiosis. They are one of the most common causes of childhood diarrhoea worldwide, and infection can have prolonged detrimental effects on the development of children, but also can be life threatening to HIV/AIDS patients and transplant recipients. A variety of hosts can act as reservoirs, and Cryptosporidium can persist in the environment for prolonged times as oocysts. While there has been substantial interest in these parasites, there is very little progress in terms of treatment development and understanding the majority of the life cycle of this unusual organism. In this review, we will provide an overview on the existing knowledge of the biology of the parasite and the current progress in developing in vitro cultivation systems. We will then describe a synopsis of current and next generation approaches that could spearhead further research in combating the parasite

Novel Experimental Simulations of the Atmospheric Injection of Meteoric Metals

A newly developed laboratory, Meteoric Ablation Simulator (MASI), is used to test model predictions of the atmospheric ablation of interplanetary dust particles (IDPs) with experimental Na, Fe, and Ca vaporization profiles. MASI is the first laboratory setup capable of performing time-resolved atmospheric ablation simulations, by means of precision resistive heating and atomic laser-induced fluorescence detection. Experiments using meteoritic IDP analogues show that at least three mineral phases (Na-rich plagioclase, metal sulfide, and Mg-rich silicate) are required to explain the observed appearance temperatures of the vaporized elements. Low melting temperatures of Na-rich plagioclase and metal sulfide, compared to silicate grains, preclude equilibration of all the elemental constituents in a single melt. The phase-change process of distinct mineral components determines the way in which Na and Fe evaporate. Ca evaporation is dependent on particle size and on the initial composition of the molten silicate. Measured vaporized fractions of Na, Fe, and Ca as a function of particle size and speed confirm differential ablation (i.e., the most volatile elements such as Na ablate first, followed by the main constituents Fe, Mg, and Si, and finally the most refractory elements such as Ca). The Chemical Ablation Model (CABMOD) provides a reasonable approximation to this effect based on chemical fractionation of a molten silicate in thermodynamic equilibrium, even though the compositional and geometric description of IDPs is simplistic. Improvements in the model are required in order to better reproduce the specific shape of the elemental ablation profiles