Integrated ultrasonic particle positioning and low excitation light fluorescence imaging

A compact hybrid system has been developed to position and detect fluorescent micro-particles by combining a Single Photon Avalanche Diode (SPAD) imager with an acoustic manipulator. The detector comprises a SPAD array, light-emitting diode (LED), lenses, and optical filters. The acoustic device is formed of multiple transducers surrounding an octagonal cavity. By stimulating pairs of transducers simultaneously, an acoustic landscape is created causing fluorescent micro-particles to agglomerate into lines. The fluorescent pattern is excited by a low power LED and detected by the SPAD imager. Our technique combines particle manipulation and visualization in a compact, low power, portable setup

Chemochemical caries removal: a review of the techniques and latest developments

Chemomechanical caries removal involves the chemical softening of carious dentine followed by its removal by gentle excavation. The reagent involved is generated by mixing amino acids with sodium hypochlorite; N-monochloroamino acids are formed which selectively degrade demineralised collagen in carious dentine. The procedure requires 5-15 minutes but avoids the painful removal of sound dentine thereby reducing the need for local anaesthesia. It is well suited to the treatment of deciduous teeth, dental phobics and medically compromised patients. The dentine surface formed is highly irregular and well suited to bonding with composite resin or glass ionomer. When complete caries removal is achieved, the dentine remaining is sound and properly mineralised. The system was originally marketed in the USA in the 1980's as Caridex. Large volumes of solution and a special applicator system were required. A new system, Carisolv, has recently been launched on to the market. This comes as a gel, requires volumes of 0.2-1.0 ml and is accompanied by specially designed instruments

Wide-Range Optical CMOS-Based Diagnostics

Colorimetric, chemiluminescence and refractive index based diagnostics are some of the most important sensing techniques in biomedical science and clinical medicine. Conventionally laboratories and medical clinics rely on bulky and dedicated equipment for each diagnostic technique independently. In this paper, we present CMOS sensor based solutions, comprising a single photon avalanche detector array and photodiode array. The CMOS platform offers low cost integration and wide range of light-based diagnostic techniques, leading to development of point-of-care devices

Interactive manipulation of microparticles in an octagonal sonotweezer

An ultrasonic device for micro-patterning and precision manipulation of micrometre-scale particles is demonstrated. The device is formed using eight piezoelectric transducers shaped into an octagonal cavity. By exciting combinations of transducers simultaneously, with a controlled phase delay between them, different acoustic landscapes can be created, patterning micro-particles into lines, squares, and more complex shapes. When operated with all eight transducers the device can, with appropriate phase control, manipulate the two dimensional acoustic pressure gradient; it thus has the ability to position and translate a single tweezing zone to different locations on a surface in a precise and programmable manner

Clostridium difficile Toxin in Adult Inpatients in an Urban Hospital in Malawi: Associations with HIV Status, CD4 Count and Diarrhoea

Clostridium difficile Infection (CDI) is the cause of substantial morbidity and mortality in the developed world. However, very little is known about the burden of CDI in sub-Saharan Africa where less antibiotic restriction, high HIV prevalence and greater impact from nosocomial infection mean the potential for a significant disease burden is great. Researchers investigated the prevalence of Clostridium difficile Toxin (CDT), assessing association with HIV, CD4 count and diarrhoea in medical in-patients in Malawi. In 206 patients tested for CDT, 28 (13.6%) were positive. No significant associations were seen with either diarrhoea or HIV. There was a non-statistically significant (p = 0.056) association between CD4 counts of <50 and CDT. The frequency and the clinical implications of CDI in both HIV positive and negative patients in sub-Saharan Africa, requires further assessment

Progress Towards a Multi-Modal Capsule Endoscopy Device Featuring Microultrasound Imaging

Current clinical standards for endoscopy in the gastrointestinal (GI) tract combine high definition optics and ultrasound imaging to view the lumen superficially and through its thickness. However, these instruments are limited to the length of an endoscope and the only clinically available, autonomous devices able to travel the full length of the GI tract easily offer only video capsule endoscopy (VCE). Our work seeks to overcome this limitation with a device (“Sonopill”) for multimodal capsule endoscopy, providing optical and microultrasound (μUS) imaging and supporting sensors1. μUS transducers have been developed with multiple piezoelectric materials operating across a range of centre frequencies to study viability in the GI tract. Because of the combined constraints of μUS imaging and the low power / heat tolerance of autonomous devices, a hybrid approach has been taken to the transducer design, with separate transmit and receive arrays allowing multiple manufacturing approaches to maximise system efficiency. To explore these approaches fully, prototype devices have been developed with PVDF, high-frequency PZT and PMN-PT composites, and piezoelectric micromachined ultrasonic transducer arrays. Test capsules have been developed using 3D printing to investigate issues including power consumption, heat generation / dissipation, acoustic coupling, signal strength and capsule integrity. Because of the high functional density of the electronics in our proposed system, application specific integrated circuits (ASICs) have been developed to realise the ultrasound transmit and receive circuitry along with white-light and autofluorescence imaging with single-photon avalanche detectors (SPADs). The ultrasound ASIC has been developed and the SPAD electronics and optical subsystem have been validated experimentally. The functionality of various transducer materials has been examined as a function of frequency and ultrasound transducers have been developed to operate at centre frequencies in the range 15 - 50 MHz. Ex vivo testing of porcine tissue has been performed, generating images of interest to the clinical community, demonstrating the viability of the Sonopill concept

A colorimetric CMOS-based platform for rapid total serum cholesterol quantification

Elevated cholesterol levels are associated with a greater risk of developing cardiovascular disease and other illnesses, making it a prime candidate for detection on a disposable biosensor for rapid point of care diagnostics. One of the methods to quantify cholesterol levels in human blood serum uses an optically mediated enzyme assay and a bench top spectrophotometer. The bulkiness and power hungry nature of the equipment limits its usage to laboratories. Here, we present a new disposable sensing platform that is based on a complementary metal oxide semiconductor process for total cholesterol quantification in pure blood serum. The platform that we implemented comprises readily mass-manufacturable components that exploit colorimetric changes of cholesterol oxidase and cholesterol esterase reactions. We have shown that our quantification results are comparable to that obtained by a bench top spectrophotometer. Using the implemented device, we have measured cholesterol concentration in human blood serum as low as 29 μM with a limit of detection at 13 μM, which is approximately 400 times lower than average physiological range, implying that our device also has the potential to be used for applications that require greater sensitivity

Genevan encounters with Newton. Gabriel Cramer, Jean-Louis Calandrini and the annotated edition of the Principia

The named editors of the annotated edition of Newton’s Principia, François Jacquier and Thomas Le Seur, saw their painstaking enterprise as a decisive means to making the great polymath’s work more accessible. As this article makes clear, the Genevan edition was above all a collaborative enterprise, resting crucially on the contributions of the two Genevan mathematicians Jean-Louis Calandrini and Gabriel Cramer, both of whose expertise complemented and, in some respects, exceeded that of the two Minim priests based in Rome, while also being attuned to contemporary scientific discussion involving the foremost scientific figures of the time, such as Euler, Clairaut, d’Alembert and the Bernoulli. Focusing in particular on the debate over Newton’s theory of the Moon, the article reveals the importance of Calandrini’s and Cramer’s scientific networks for understanding the production and reception of the Geneva edition. This article is part of the theme issue ‘Newton, Principia, Newton Geneva Edition (17th–19th) and modern Newtonian mechanics: heritage, past & present’

MA

thesisThe material presented and analyzed in this paper was excavated in November 1939 by Professor Elmer R. Smith, Dr. C. E. Dibble and a group of about one hundred students in archeology from the University of Utah. The artifacts were catalogued and classified "by Dr. Dibble. As in any other archeological investigation, the problem is threefold; (1), to identify the people whose material culture has been recovered; (2), to find out to what other-peoples in the same area they were related culturally; and (3), to determine the period of time they occupied the area

Physical arguments and moral inducements: John Wallis on questions of antiquarianism and natural philosophy

In his posthumously published work Chartham News (1669), the antiquary William Somner tentatively sought to link the discovery of fossilized remains near Canterbury to the prehistoric existence of an isthmus connecting Britain and France, before calling on natural philosophers to pursue his explanation further. This call was eventually heeded by the Oxford mathematician John Wallis, but only after more than thirty years had elapsed. The arrival in England of a catalogue of questions concerning the geology of the Channel led to the republication of Chartham News in the Philosophical Transactions, prompting Wallis to develop a physical explanation based on his intimate knowledge of the Kent coastline. Unbeknown to Wallis at the time, that catalogue had been sent by G. W. Leibniz, who had in turn received it from G. D. Schmidt, the former Resident of Brunswick-Lüneburg in Sweden. Wallis's explanation, based on the principle of establishing physical causes both for the rupturing of the isthmus and for the origin of fossils, placed him in a camp opposed by Newtonian authors such as John Harris at a time when the priority dispute over the discovery of the calculus led to the severing of his ties with the German mathematician and philosopher Leibniz