Temperature-modulated graphene oxide resistive humidity sensor for indoor air quality monitoring.

In this paper we present a temperature-modulated graphene oxide (GO) resistive humidity sensor that employs complementary-metal-oxide-semiconductor (CMOS) micro-electro-mechanical-system (MEMS) micro-hotplate technology for the monitoring and control of indoor air quality (IAQ). GO powder is obtained by chemical exfoliation, dispersed in water and deposited via ink-jet printing onto a low power micro-hotplate. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) show the typical layered and wrinkled morphology of the GO. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red (FTIR) spectroscopy indicate that the GO flakes possess a significant number of oxygen containing functional groups (epoxy, carbonyl, hydroxyl) extremely attractive for humidity detection. Electro-thermal characterisation of the micro-hotplates shows a thermal efficiency of 0.11 mW per °C, resulting in a sensor DC power consumption of only 2.75 mW at 50 °C. When operated in an isothermal mode, the sensor response is detrimentally affected by significant drift, hysteretic behaviour, slow response/recovery times and hence poor RH level discrimination. Conversely, a temperature modulation technique coupled with a differential readout methodology results in a significant reduction of the sensor drift, improved linear response with a sensitivity of 0.14 mV per %, resolution below 5%, and a maximum hysteresis of ±5%; response and recovery times equal to 189 ± 49 s and 89 ± 5 s, respectively. These performance parameters satisfy current IAQ monitoring requirements. We have thus demonstrated the effectiveness of integrating GO on a micro-hotplate CMOS-compatible platform enabling temperature modulation schemes to be easily applied in order to achieve compact, low power, low cost humidity IAQ monitoring.

Mask-less deposition of Au-SnO2 nanocomposites on CMOS MEMS platform for ethanol detection.

Here we report on the mask-less deposition of Au-SnO2 nanocomposites with a silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) micro electro mechanical system (MEMS) platform through the use of dip pen nanolithography (DPN) to create a low-cost ethanol sensor. MEMS technology is used in order to achieve low power consumption, by the employment of a membrane structure formed using deep reactive ion etching technique. The device consists of an embedded tungsten micro-heater with gold interdigitated electrodes on top of the SOI membrane. The tungsten micro-heater is used to raise the membrane temperature up to its operating temperature and the electrodes are used to measure the resistance of the nanocomposite sensing layer. The CMOS MEMS devices have high electro-thermal efficiency, with 8.2 °C temperature increase per mW power of consumption. The sensing material (Au-SnO2 nanocomposite) was synthesised starting from SnO nanoplates, then Au nanoparticles were attached chemically to the surface of SnO nanoplates, finally the mixture was heated at 700 °C in an oven in air for 4 h. This composite material was sonicated for 2 h in terpineol to make a viscous homogeneous slurry and then 'written' directly across the electrode area using the DPN technique without any mask. The devices were characterised by exposure to ethanol vapour in humid air in the concentration range of 100-1000 ppm. The sensitivity varied from 1.2 to 0.27 ppm(-1) for 100-1000 ppm of ethanol at 10% relative humid air. Selectivity measurements showed that the sensors were selective towards ethanol when they were exposed to acetone and toluene.

CMOS integration of inkjet-printed graphene for humidity sensing.

We report on the integration of inkjet-printed graphene with a CMOS micro-electro-mechanical-system (MEMS) microhotplate for humidity sensing. The graphene ink is produced via ultrasonic assisted liquid phase exfoliation in isopropyl alcohol (IPA) using polyvinyl pyrrolidone (PVP) polymer as the stabilizer. We formulate inks with different graphene concentrations, which are then deposited through inkjet printing over predefined interdigitated gold electrodes on a CMOS microhotplate. The graphene flakes form a percolating network to render the resultant graphene-PVP thin film conductive, which varies in presence of humidity due to swelling of the hygroscopic PVP host. When the sensors are exposed to relative humidity ranging from 10-80%, we observe significant changes in resistance with increasing sensitivity from the amount of graphene in the inks. Our sensors show excellent repeatability and stability, over a period of several weeks. The location specific deposition of functional graphene ink onto a low cost CMOS platform has the potential for high volume, economic manufacturing and application as a new generation of miniature, low power humidity sensors for the internet of things.

Biosynthetic infochemical communication.

There is an ever-increasing demand for data to be embedded in our environment at ever-decreasing temporal and spatial scales. Whilst current communication and storage technologies generally exploit the electromagnetic properties of media, chemistry offers us a new alternative for nanoscale signaling using molecules as messengers with high information content. Biological systems effectively overcome the challenges of chemical communication using highly specific biosynthetic pathways for signal generation together with specialized protein receptors and nervous systems. Here we consider a new approach for information transmission based upon nature's quintessential example of infochemical communication, the moth pheromone system. To approach the sensitivity, specificity and versatility of infochemical communication seen in nature, we describe an array of biologically-inspired technologies for the production, transmission, detection, and processing of molecular signals. We show how it is possible to implement each step of the moth pheromone pathway for biosynthesis, transmission, receptor protein binding/transduction, and antennal lobe processing of monomolecular and multimolecular signals. For each implemented step, we discuss the value, current limitations, and challenges for the future development and integration of infochemical communication technologies. Together, these building blocks provide a starting point for future technologies that can utilize programmable emission and detection of multimolecular information for a new and robust means of communicating chemical information.

Mimicking the biological olfactory system: a Portable electronic Mucosa.

In this study the authors report on the development of a new type of electronic nose (e-nose) instrument, which the authors refer to as the Portable electronic Mucosa (PeM) as a continuation of previous research. It is designed to mimic the human nose by taking significant biological features and replicating them electronically. The term electronic mucosa or simply e-mucosa was used because our e-nose emulates the nasal chromatographic effect discovered in the olfactory epithelium, located within the upper turbinate. The e-mucosa generates spatio-temporal information that the authors believe could lead to improved odour discrimination. The PeM comprises three large sensor arrays each containing a total of 576 sensors, with 24 different coatings, to increase the odour selectivity. The nasal chromatographic effect provides temporal information in the human olfactory system, and is mimicked here using two-coated retentive channels. These channels are coated with polar and non-polar compounds to enhance the selectivity of the instrument. Thus, for an unknown sample, the authors have both the spatial information (as with a traditional e-nose) and the temporal information. The authors believe that this PeM may offer a way forward in developing a new range of low-cost e-noses with superior odour specificity.

Towards a truly biomimetic olfactory microsystem: an artificial olfactory mucosa.

Today, the capability of the human olfactory system is still, in many ways, superior to that of the electronic nose. Although electronic noses are often compared with their biological counterpart, they neither mimic its neural architecture nor achieve its discriminating performance. Experimental studies on the mammalian olfactory system suggest that the nasal cavity, comprising of the mucous layer and the olfactory epithelium, performs a degree of chromatographic separation of complex mixtures. Thus receptor cells distributed beneath the mucous layer provide both spatial and temporal chemosensory information. Here we report on the development of an artificial olfactory microsystem that replicates this basic structure. This contains an integrated channel to emulate the nasal cavity and coated with a polymer to mimic the partitioning mucous layer, which is positioned directly over a sensor array. Our system employs an 80 element chemoresistive microsensor array with carbon black/polymer odour-sensitive films combined with a microfluidic package fabricated by micro-stereolithography. Results show that this biomimetic system generates both spatial and temporal odorant signals, with a temporal chemical retention period of up to 170 s. Data analysis has revealed improvements in its ability to discriminate between two simple odours and a set of complex odours. We believe such emulation of the olfactory system can lead to improved odour discrimination within the field of electronic noses.

Data reduction in headspace analysis of blood and urine samples for robust bacterial identification.

This paper demonstrates the application of chemical headspace analysis to the problem of classifying the presence of bacteria in biomedical samples by using computational tools. Blood and urine samples of disparate forms were analysed using a Cyrano Sciences C320 electronic nose together with an Agilent 4440 Chemosensor. The high dimensional data sets resulting from these devices present computational problems for parameter estimation of discriminant models. A variety of data reduction and pattern recognition techniques were employed in an attempt to optimise the classification process. A 100% successful classification rate for the blood data from the Agilent 4440 was achieved by combining a Sammon mapping with a radial basis function neural network. In comparison a successful classification rate of 80% was achieved for the urine data from the C320 which were analysed using a novel nonlinear time series model.

Clinical evaluation of the electronic nose in the diagnosis of ear, nose and throat infection: a preliminary study.

The term electronic nose describes an electronic system that is able to mimic the human sense of smell. Electronic noses have been developed over the last 10 or more years to perform a variety of identification tasks in various industries. More recently electronic noses have attracted new interest in their application in the field of medical diagnosis. The aim of this study is to explore the use of an electronic nose to identify and classify pathogens associated with ear, nose and throat (ENT) infections. In this study 90 bacterial swab samples were collected from 90 patients with ENT infections. Some of these samples were analysed immediately with a commercial electronic nose (Cyranose C320). Similar numbers of swabs were also taken from the same site of infection and were sent for microbiology culture and sensitivity. The electronic nose diagnosis was compared with the microbiology diagnosis and it was found that the electronic nose diagnosis was correct in 88.2 per cent of the cases, which is an encouraging result.

Electronic nose based tea quality standardization.

In this paper we have used a metal oxide sensor (MOS) based electronic nose (EN) to analyze five tea samples with different qualities, namely, drier month, drier month again over-fired, well fermented normal fired in oven, well fermented overfired in oven, and under fermented normal fired in oven. The flavour of tea is determined mainly by its taste and smell, which is generated by hundreds of Volatile Organic Compounds (VOCs) and Non-Volatile Organic Compounds present in tea. These VOCs are present in different ratios and determine the quality of the tea. For example Assamica (Sri Lanka and Assam Tea) and Assamica Sinesis (Darjeeling and Japanese Tea) are two different species of tea giving different flavour notes. Tea flavour is traditionally measured through the use of a combination of conventional analytical instrumentation and human or ganoleptic profiling panels. These methods are expensive in terms of time and labour and also inaccurate because of a lack of either sensitivity or quantitative information. In this paper an investigation has been made to determine the flavours of different tea samples using an EN and to explore the possibility of replacing existing analytical and profiling panel methods. The technique uses an array of 4 MOSs, each of, which has an electrical resistance that has partial sensitivity to the headspace of tea. The signals from the sensor array are then conditioned by suitable interface circuitry. The data were processed using Principal Components Analysis (PCA), Fuzzy C Means algorithm (FCM). We also explored the use of a Self-Organizing Map (SOM) method along with a Radial Basis Function network (RBF) and a Probabilistic Neural Network classifier. Using FCM and SOM feature extraction techniques along with RBF neural network we achieved 100% correct classification for the five different tea samples with different qualities. These results prove that our EN is capable of discriminating between the flavours of teas manufactured under different processing conditions, viz. over-fermented, over-fired, under fermented, etc.

Long-term follow-up after exertional heat illness during recruit training.

PURPOSE: To evaluate long-term susceptibility to subsequent serious exertional heat illness (EHI) in military recruits who suffered exertional heat illness during basic training. METHODS: We identified Marine Corps members who completed at least 6 months of military service and suffered EHI treated as outpatients (N = 872) or inpatients (N = 50) during basic training in 1979-1991 at the Parris Island Marine Corps Recruit Depot, SC (EHI cases). We compared them to 1391 similar members (noncases) who did not experience EHI during basic training. These subjects were followed from 6 months after accession into the military through the subsequent 4 yr. Follow-up was through military personnel records to determine retention and military hospital databases to determine subsequent hospitalizations during military service. RESULTS: Military retention rates were slightly lower for those who suffered EHI during basic training, compared with those who did not (24% vs 30% at 4 yr, respectively). Outpatient EHI cases also had about 40% higher subsequent hospitalization rates in military hospitals than noncases during their continued military service, although these differences declined over time and diagnoses showed little relationship to EHI. EHI cases had higher rates of subsequent hospitalization for EHI, but the number was too small (five hospitalizations) to provide stable comparisons. CONCLUSION: Hospitalization for EHI is uncommon during subsequent military service after an initial episode during basic training, and occurrence of EHI during basic training has only a small impact on subsequent military retention and hospitalization.

The Department of Defense Medical Mortality Registry.

The Department of Defense Medical Mortality Registry is being implemented at the Office of the Armed Forces Medical Examiner, Armed Forces Institute of Pathology, providing the first comprehensive medical mortality surveillance for the Department of Defense. The Registry attempts to obtain complete medical and circumstantial information on every military active duty death for medical surveillance and prevention research. Medical records, autopsy reports, eyewitness accounts, and investigative reports are reviewed to validate and synthesize medical, circumstantial, and risk factor information on each death. All military active duty deaths since 1980 are currently identified and classified by manner of death (accident, suicide, homicide, illness, hostile, undetermined). Military death rates have decreased during the past two decades by nearly half. About three-quarters of military deaths are attributable to injury (accident, suicide, homicide). The Registry creates new opportunities for prevention-oriented research as it collects detailed information on every military death.

Cigarette smoking and exercise-related injuries among young men and women.

BACKGROUND: We evaluate whether a recent history of cigarette smoking is a risk factor for exercise-related injuries sustained during Army basic training, controlling for factors such as demographic, physical fitness, and health variables. METHODS: We conducted an observational cohort study in 1087 male and 915 female Army recruits undergoing 8-week basic military training. Data were collected from questionnaires, anthropometric measurements, physical fitness tests, company training logs, and medical records of all clinic visits. RESULTS: During the 8-week training period, 33% of men and 50% of women had at least one clinic visit for injury, including 14% of men and 25% of women who lost more than 5 days of training due to injury. Recruits who reported smoking at least one cigarette in the month prior to beginning basic training (which was conducted in a smoke-free environment) had significantly higher injury rates during training than those who did not report smoking (40% versus 29% for men, and 56% versus 46% for women). The relationship with smoking history was present most strongly for overuse injuries (32% versus 24% in men and 51% versus 40% in women). Multiple logistic regression analyses controlling for all other factors consistently showed adjusted odds ratios of about 1.5 for injury rate in those with a history of smoking compared to those without. CONCLUSIONS: The association of history of cigarette smoking with injury occurrence was consistent throughout the analyses, with very little confounding by other factors. The detrimental effects of smoking on injuries appears to persist at least several weeks after cessation of smoking.

Effect of rest from running on overuse injuries in army basic training.

BACKGROUND: It has been hypothesized that a period of rest from running in the early weeks of basic military training will prevent stress fractures among recruits. DESIGN: Modification of running schedules in companies of Army recruits undergoing basic military training was assigned. SETTING/PARTICIPANTS: Six male training companies were enrolled and followed during their 8 weeks of basic military training at Fort Bliss, Texas, in summer/fall 1989. INTERVENTION: Intervention companies were asked to rest from running during the second, third, or fourth week of basic military training. MAIN OUTCOME MEASURES: Data were collected from questionnaires, anthropometric measurements, Army physical fitness tests, company training logs, and medical record abstraction of all clinic visits. RESULTS: Among the 1357 enrolled male recruits, there were 236 (17%) with overuse injury and 144 (11%) with traumatic injury, resulting in 535 clinic visits and 1927 training days lost. Stress fracture/reaction rates varied from 3 to 8 per 100 recruits among the intervention companies and 2 to 7 per 100 recruits among the non-intervention companies. Total injury rates were 18 to 35 per 100 recruits in the intervention companies and 18 to 29 per 100 recruits in the non-intervention companies. CONCLUSIONS: The study provided no evidence for a protective effect on overuse injuries of resting from running for 1 week early in basic military training. There was varied physical training among the companies, however, with variation of injury rates that likely related to factors other than the intervention.

The Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine: status of the Federal Medical School after 25 years.

In its first 25 years, the Uniformed Services University of the Health Sciences (USUHS) has become a quality institution of medical education that provides a steady flow of career physicians for the military. It compares favorably with U.S. medical school averages in all aspects of undergraduate medical education: faculty, teaching facilities, matriculants, curriculum, student performance, and cost. USUHS provides excellent medical education and adds unique preparation for uniformed public service. It also provides military-specific graduate education, graduate medical education, continuing health education, medical research, clinical services, consultation, public service, and ties with international military, medical, and research institutions.

The extent of military medicine topics taught in military family practice residency programs: Part I. A survey of current military family practice residency directors.

The Military Unique Curricula (MUC) was published in 1988 as a guideline for instruction at military residencies in military-specific topics. To evaluate the degree of implementation and the perceived necessity of the MUC curricula and the attitudes and logistical factors relevant to military medicine instruction in military family practice residencies, questionnaires were sent to all 18 military family practice residency directors. The results reveal a wide range of opinions regarding the importance of military medicine and the amount of instruction of military medicine topics among the residency programs. The total number of topics taught was correlated (p < 0.05) with years as residency director, awareness of the MUC, and an opinion that the material would not be better taught at service-specific schools. There appears to have been little influence of the MUC on the curricula of military family practice residencies since its publication.