Identification and characterisation of Staphylococcus aureus on low cost screen printed carbon electrodes using impedance spectroscopy.

Staphylococcus aureus infections are a cause of significant morbidity and mortality, in addition to representing a considerable economic burden. The aim of this study was to explore a low cost screen printed electrode as a sensor for the detection of S. aureus using impedance spectroscopy. S. aureus was incubated in chambers containing the electrodes and the results analysed using a novel normalisation approach. These results show that it is possible to detect the presence of S. aureus in LB media after 30 min incubation of a 1% growth culture, in addition to being able to see immediate cell concentration dependant changes in 0.9% NaCl. These observations imply that a number of electrochemical mechanisms cause a change in the impedance as a result of the presence of S. aureus, including adsorption to the electrode surface and the metabolism of the bacteria during growth. The study suggests that this detection approach would be useful in a number of clinical scenarios where S. aureus leads to difficult to treat infections.

Assessment of the 2D:4D ratio in aggression-related injuries in children attending a paediatric emergency department.

BACKGROUND: The 2D:4D ratio is a sexually dimorphic trait. A lower ratio is correlated with sporting prowess, successful financial trading, risk taking behaviour, aggression, and aggression-related injuries, such as the fifth metacarpal fractures. AIMS: We aimed to assess if the ratio correlates to skeletally immature patient aggression. METHODS: Radiology reports were searched for the terms "5th metacarpal" or "boxer". Of 537 X-rays, 142 had fractures. The mechanism of injury was recorded in 102 patients, differentiating aggressive and non-aggressive injury groups. Bone age and chronological age were recorded. RESULTS: A clear male preponderance for aggression was identified with only 60% of non-aggressive injuries occurring in males compared to 95% in the aggression group (p < 0.001). Patients with aggression injuries were older chronologically (14.6 vs 12.7, p < 0.001) and by bone age (14.5 vs 13.0, p < 0.001). For male patients, there was no difference in the 2D:4D ratio (p = 0.94); however, for females, the difference was significant (p = 0.04). CONCLUSIONS: Aggression injuries occur at an older age and are more common in males. In the female cohort, there was a distinct difference in digit ratio.

A potential hidden layer of meteorites below the ice surface of Antarctica.

Antarctica contains some of the most productive regions on Earth for collecting meteorites. These small areas of glacial ice are known as meteorite stranding zones, where upward-flowing ice combines with high ablation rates to concentrate large numbers of englacially transported meteorites onto their surface. However, meteorite collection data shows that iron and stony-iron meteorites are significantly under-represented from these regions as compared with all other sites on Earth. Here we explain how this discrepancy may be due to englacial solar warming, whereby meteorites a few tens of centimetres below the ice surface can be warmed up enough to cause melting of their surrounding ice and sink downwards. We show that meteorites with a high-enough thermal conductivity (for example, iron meteorites) can sink at a rate sufficient to offset the total annual upward ice transport, which may therefore permanently trap them below the ice surface and explain their absence from collection data.

Factors determining the most efficient spray distribution for marine cloud brightening.

We investigate the sensitivity of marine cloud brightening to the properties of the added salt particle distribution using a cloud parcel model, with an aim to address the question of, 'what is the most efficient particle size distribution that will produce a desired cooling effect?' We examine the effect that altering the aerosol particle size distribution has on the activation and growth of drops, i.e. the Twomey effect alone, and do not consider macrophysical cloud responses that may enhance or mitigate the Twomey effect. For all four spray generation methods considered, Rayleigh jet; Taylor cone jet; supercritical fluid; and effervescent spray, salt particles within the median dry diameter range Dm=30-100 nm are the most effective range of sizes. The Rayleigh jet method is also the most energy efficient overall. We also find that care needs to be taken when using droplet activation parametrizations: for the concentrations considered, Aitken particles do not result in a decrease in the total albedo, as was found in a recent study, and such findings are likely to be a result of the parametrizations' inability to simulate the effect of swollen aerosol particles. Our findings suggest that interstitial aerosol particles play a role in controlling the albedo rather than just the activated cloud drops, which is an effect that the parametrization methods do not consider.

The influence of different dressings on the pH of the wound environment.

OBJECTIVE: This study examines the effect of various wound dressings on the pH levels of a wound, using a simulated wound environment. METHOD: The pH levels of a 4 different wound dressings (manuka honey dressing, sodium carboxymethylcellulose hydrofiber dressing, polyhydrated ionogen-coated polymer mesh dressing, and a protease modulating collagen cellulose dressing) were tested in a simulated horse serum wound environment. The effect of local buffering was observed and pH changes in real time were measured. RESULTS: All dressings were found to have low pH (below pH 4), with the lowest being the protease modulating collage cellulose dressing, with a pH of 2.3. The dressing with the strongest acid concentration was the polyhydrated, ionogen-coated, polymer mesh dressing. CONCLUSION: The low pH and strong acidic nature of the dressing investigated indicate that they may play a role in influencing the healing process in a wound. DECLARATION OF INTEREST: The authors have no conflicts of interest to declare. This study was funded by the EPSRC.

Kinetics of transient hiatus hernia during transient lower esophageal sphincter relaxations and swallows in healthy subjects.

BACKGROUND: Proximal displacement of the gastro-esophageal junction (GEJ) is present in hiatus hernia but also occurs transiently during transient lower esophageal sphincter relaxations (TLESRs) and swallows. Using a novel magnetic-based technique we have performed detailed examination of the GEJ movement during TLESRs and swallows in healthy subjects. METHODS: In 12 subjects, a magnet was endoscopically clipped to the GEJ and combined assembly of Hall-Effect locator probe and 36 channel high-resolution manometer passed nasally. After a test meal the subjects were studied for 90 min. KEY RESULTS: The median amplitude of proximal movement of GEJ during TLESRs was 4.3 cm (1.6-8.8 cm) and this was substantially greater than during swallowing at 1.2 cm (0.4-2.7 cm), P = 0.002. With both TLESRs and swallows proximal GEJ movement coincided with lower esophageal sphincter (LES) relaxation and return to its original position occurred 4 s after return of LES tone. Kinetic modeling of the movement of the GEJ during TLESRs indicated two return phases with the initial return phase having the greater velocity (0.9 cm s(-1) ) and being strongly correlated with amplitude of proximal movement (r = 0.8, P < 0.001). CONCLUSIONS & INFERENCES: The marked proximal GEJ migration during TLESRs represents very severe herniation of the GEJ. The rapid initial return of the GEJ following TLESRs when the crural diaphragm is relaxed and its correlation with amplitude suggest it is due to elastic recoil of the phreno-esophageal ligament. The marked stretching of the phreno-esophageal ligament during TLESRs may contribute to its weakening and development of established hiatus hernia.

Whole body MRI in the diagnosis of chronic recurrent multifocal osteomyelitis.

Chronic recurrent multifocal osteomyelitis (CRMO) is a diagnosis of exclusion primarily in children and adolescents. As part of the essential criteria for the diagnosis of CRMO, multifocal lesions must be identified. We present the case of an 11-year-old boy with CRMO, whose diagnosis was facilitated by the use of whole body magnetic resonance imaging (WBMR), but not isotope bone scanning.

High-resolution esophageal manometry: addressing thermal drift of the manoscan system.

BACKGROUND: The high resolution esophageal manometry system manufactured by Sierra Scientific Instruments is widely used. The technology is liable to 'thermal drift', a change in measured pressure due to change in temperature. This study aims to characterize 'thermal drift' and minimize its impact. METHODS: Response of the system to immediate temperature change (20 °C to 37 °C) was tested. Accuracy of pressure measurement over two hours at 37 °C was examined. Six repetitions were performed and median pressure change calculated for each sensor. Sensors were compared using Kruskal-Wallis test. Current correction processes were tested. KEY RESULTS: There was a biphasic response of the system to body temperature: an immediate change in recorded pressure, 'thermal effect' and an ongoing pressure change with time, 'baseline drift'. Median thermal effect for all 36 sensors was 7 mmHg (IQR 3.8 mmHg). Median baseline drift was 11.1 mmHg (IQR 9.9 mmHg). Baseline drift varied between sensors but for a given sensor was linear. Interpolated thermal compensation, recommended for prolonged studies, corrects data assuming a linear drift of pressures. When pressures were corrected in this way, baseline pressure was almost restored to zero (Median 0.3 mmHg, IQR 0.3). The standard thermal compensation process did not address the error associated with baseline drift. CONCLUSIONS & INFERENCES: Thermal effect is well compensated in the current operation of the system but baseline drift is not well recognized or addressed. Incorporation of a linear correction into current software would improve accuracy without impact on ease of use.

Predicting the human in vivo performance of different oral capsule shell types using a novel in vitro dynamic gastric model.

The disintegration of a capsule shell may determine the onset of drug dissolution from capsule formulations. In this study, the release of a rapidly dissolving model drug (paracetamol), from two hydroxypropyl methylcellulose capsules containing either carageenan (HPMC-C) or gellan gum (HPMC-G) and one hard gelatin (HG) capsule, were investigated using a conventional in vitro model, the USP dissolution apparatus I, and a novel in vitro model of the human gastric compartment, the dynamic gastric model (DGM). The results obtained in vitro were compared with in vivo gamma scintigraphy human data and in vivo gastric emptying profiles available in the literature. The drug release from HPMC-G capsules, observed with the USP dissolution apparatus I, was delayed with respect to the other two capsules, while the results obtained from the DGM in the fasted state were closer together, which was in agreement with data from the in vivo studies. In the fasted state, the capsule rupture times obtained from the DGM were similar to those observed by gamma scintigraphy in vivo studies. In the fed state, the 'apparent' rupture times observed with the DGM were delayed compared to fasted, and were even longer than those observed by scintigraphy in vivo for HPMC-G and HG capsules. However, these discrepancies can reasonably be explained by considering the impact of food upon dispersion of the capsule contents and the sampling from the DGM, when compared to the human scintigraphy experiments.

MRI studies of the hydrodynamics in a USP 4 dissolution testing cell.

We present a detailed study of hydrodynamics inside the flow-through dissolution apparatus when operated according to USP recommendations. The pulsatile flow inside the flow-through cell was measured quantitatively using magnetic resonance imaging (MRI) at a spatial resolution of 234 × 234 µm(2) and slice thickness of 1 mm. We report the experimental protocols developed for in situ MRI studies and the effect that the operating conditions and tablet orientation have on the hydrodynamics inside commercial flow cells. It was found that the flow field inside the dissolution cells was, at most operating conditions, heterogeneous, rather than fully developed laminar flow, and characterised by re-circulation and backward flow. A model tablet was shown to be contacted by a wide distribution of local velocities as a function of position and orientation in the flow cell. The use of 1 mm beads acted as a distributor of the flow but did not suffice to ensure a fully developed laminar flow profile. These results emphasise the necessity to understand the influence of test conditions on dissolution behaviour in defining robust flow-through dissolution methods.

Diagnosis of acute pulmonary histoplasmosis by antigen detection.

BACKGROUND: Antigen detection, which has proven useful in diagnosis of disseminated histoplasmosis, has not been studied in acute pulmonary histoplasmosis (APH). Because treatment is indicated in most patients with moderately severe or severe APH, antigen detection for rapid diagnosis could be helpful. METHODS: Histoplasma antigen detection was evaluated in 130 patients with APH. RESULTS: Antigenuria was detected in 64.6%, antigenemia in 68.6%, and antibody in 64.3%. If both urine and serum specimens were tested, antigen was detected in 82.8%, of which 45.8% had antigenemia only; and if both antigen and antibody were measured, results were positive in 93.3%, of which antigen only was positive in 35.7%. CONCLUSIONS: Testing for antigenemia, antigenuria, and antibodies using the complement fixation test offers a sensitive, noninvasive method for diagnosis of APH.

Current issues in coronary stent technology.

Coronary artery stents have become the medical device of choice for the treatment of coronary artery disease. Since their introduction in 1987, significant advances in stent technology have taken place. A major objective of these developments was the reduction of in-stent restenosis, the formation of neointimal tissue inside the stent triggered by vessel injury and the inflammatory response, which results in renarrowing of the coronary artery. Improvements in strut configuration, thickness, and materials have enhanced deliverability and reduced vessel damage. Currently available drug-eluting stents release drugs that reduce neointimal formation through the arrest of cell proliferation. Drug-eluting stents have significantly reduced rates of in-stent restenosis. However, concerns have been raised with respect to their long-term safety, particularly in relation to the occurrence of late thrombosis. The post-procedural monitoring of stent-related complications is also of interest, including the relative suitability of invasive techniques such as angiography and intravascular ultrasound, and non-invasive techniques such as computed tomography and magnetic resonance imaging scanning. This paper reviews the current issues in stent technology.

Injury of an aberrant vertebral artery during a routine corpectomy: a case report and literature review.

CASE REPORT: A case report of a 58-year-old man who sustained a laceration of his left vertebral artery during a routine corpectomy for cervical myelopathy is reported. OBJECTIVE: To report iatrogenic injury of a tortuous vertebral artery during anterior cervical spine surgery and discuss appropriate diagnosis and treatment options for this complication. SETTING: UMass Memorial Medical Center, Worcester, MA, USA. BACKGROUND DATA: Vertebral artery anomalies, although rare, are typically present with degenerative processes and great care must be taken to avoid damage during a corpectomy. Cross-sectional imaging coupled with intraoperative angiography is helpful for the urgent evaluation of the injury site and identification of the contralateral vertebral artery's status. METHODS: This is a single case of a patient sustaining a laceration of the left vertebral artery during surgery, which resulted in a lateral medullary stroke. RESULTS: After the left vertebral artery laceration, hemostasis was achieved. With the intent to better visualize and possibly embolize or stent the injury, an angiographic study was carried out. The angiogram revealed a laceration of the left vertebral artery within the vertebral foramina at vertebral body level C6, but intact distal flow. The patient underwent angiographic embolization and a subsequent magnetic resonance imaging (MRI) revealed a left lateral medullary stroke consistent with the lack of flow through the left vertebral artery from C6 to the basilar artery. CONCLUSION: If a tortuous vertebral artery is suspected, then meticulous review of preoperative cross-sectional imaging should be implemented along with angiographic examination. If anomalies are detected and the standard procedure cannot be safely carried out, then alterations, such as preoperative stent placement, need to be considered.

Improved detection of Histoplasma antigenemia following dissociation of immune complexes.

The sensitivity for detection of Histoplasma antigen is lower in serum than in urine. In other antigen assays, treatment of serum at 104 degrees C in the presence of EDTA was required for detection of antigenemia. Sensitivity and specificity for detection of Histoplasma antigenemia were examined with or without EDTA heat treatment of the serum using the MVista Histoplasma antigen enzyme immunoassay. A total of 94.6% of serum specimens from patients with AIDS and histoplasmosis that were negative untreated were positive after EDTA-heat treatment. Two-thirds of the negative serum specimens from patients with probable histoplasmosis, based upon clinical suspicion and Histoplasma antigenuria, were positive after heat treatment. Specificity was 99.0% in controls, including healthy subjects and patients in whom histoplasmosis or blastomycosis, were excluded. Precision and reproducibility were good and excellent, respectively. These findings demonstrate improvement in sensitivity without reduction in specificity, precision, or reproducibility after heat-EDTA treatment.

On diffusion processes with variable drift rates as models for decision making during learning.

We investigate Ornstein-Uhlenbeck and diffusion processes with variable drift rates as models of evidence accumulation in a visual discrimination task. We derive power-law and exponential drift-rate models and characterize how parameters of these models affect the psychometric function describing performance accuracy as a function of stimulus strength and viewing time. We fit the models to psychophysical data from monkeys learning the task to identify parameters that best capture performance as it improves with training. The most informative parameter was the overall drift rate describing the signal-to-noise ratio of the sensory evidence used to form the decision, which increased steadily with training. In contrast, secondary parameters describing the time course of the drift during motion viewing did not exhibit steady trends. The results indicate that relatively simple versions of the diffusion model can fit behavior over the course of training, thereby giving a quantitative account of learning effects on the underlying decision process.

Evaluation of morbidity, mortality and outcome following cervical spine injuries in elderly patients.

We analysed the morbidity, mortality and outcome of cervical spine injuries in patients over the age of 65 years. This study was a retrospective review of 107 elderly patients admitted to our tertiary referral spinal injuries unit with cervical spine injuries between 1994 and 2002. The data was acquired by analysis of the national spinal unit database, hospital inpatient enquiry system, chart and radiographic review. Mean age was 74 years (range 66-93 years). The male to female ratio was 2.1:1 (M = 72, F = 35). The mean follow-up was 4.4 years (1-9 years) and mean in-hospital stay was 10 days (2-90 days). The mechanism of injury was a fall in 75 and road traffic accident in the remaining 32 patients. The level involved was atlanto-axial in 44 cases, sub-axial in 52 cases and the remaining 11 had no bony injury. Multilevel involvement occurred in 48 patients. C2 dominated the single level injury and most of them were type II odontoid fractures. Four patients had complete neurology, 27 had incomplete neurology, and the remaining 76 had no neurological deficit. Treatment included cervical orthosis in 67 cases, halo immobilization in 25, posterior stabilization in 12 patients and anterior cervical fusion in three patients. The overall complication rate was 18.6% with an associated in-hospital mortality of 11.2%. The complications included loss of reduction due to halo and Minerva loosening, non-union and delayed union among conservatively treated patients, pin site and wound infection, gastrointestinal bleeding and complication due to associated injuries. Among the 28.9% patients with neurological involvement, 37.7% had significant neurological recovery. Outcome was assessed using a cervical spine outcome questionnaire from Johns Hopkins School of Medicine. Sixty-seven patients (70%) completed the form, 20 patients (19%) were deceased at review and 8 patients (7%) were uncontactable. Functional disability was more marked in the patients with neurologically deficit at time of injury. Outcome of the injury was related to increasing age, co-morbidity and the severity of neurological deficit. Injuries of the cervical spine are not infrequent occurrence in the elderly and occur with relatively minor trauma. Neck pain in the elderly patients should be thoroughly evaluated to exclude C2 injuries. Most patients can be managed in an orthosis but unstable injuries require rigid external immobilization or surgical stabilization.

The influence of small aerosol particles on the properties of water and ice clouds.

In this paper, results are presented of the influence of small organic- and soot-containing particles on the formation of water and ice clouds. There is strong evidence that these particles have grown from nano particle seeds produced by the combustion of oil products. Two series of field experiments are selected to represent the observations made. The first is the CLoud-Aerosol Characterisation Experiment (CLACE) series of experiments performed at a high Alpine site (Jungfraujoch), where cloud was in contact with the ground and the measuring station. Both water and ice clouds were examined at different times of the year. The second series of experiments is the CLOud Processing of regional Air Pollution advecting over land and sea (CLOPAP) series, where ageing pollution aerosol from UK cities was observed, from an airborne platform, to interact with warm stratocumulus cloud in a cloud-capped atmospheric boundary layer. Combining the results it is shown that aged pollution aerosol consists of an internal mixture of organics, sulfate, nitrate and ammonium, the organic component is dominated by highly oxidized secondary material. The relative contributions and absolute loadings of the components vary with location and season. However, these aerosols act as Cloud Condensation Nuclei (CCN) and much of the organic material, along with the other species, is incorporated into cloud droplets. In ice and mixed phase cloud, it is observed that very sharp transitions (extending over just a few metres) are present between highly glaciated regions and regions consisting of supercooled water. This is a unique finding; however, aircraft observations in cumulus suggest that this kind of structure may be found in these cloud types too. It is suggested that this sharp transition is caused by ice nucleation initiated by oxidised organic aerosol coated with sulfate in more polluted regions of cloud, sometimes enhanced by secondary ice particle production in these regions.

Elimination of false-positive Histoplasma antigenemia caused by human anti-rabbit antibodies in the second-generation Histoplasma antigen assay.

False-positive Histoplasma antigenemia was reported in solid organ allograft recipients who had received rabbit anti-thymocyte globulin (RATG, RATG) caused by human anti-rabbit antibodies (HARA). A second-generation Histoplasma antigen detection assay was developed to overcome false positivity caused by HARA. With the second-generation assay, false-positive results were eliminated in 18 of 19 cases without reduction in the sensitivity in patients with histoplasmosis. In fact, sensitivity for detection of antigenuria in patients with acquired immunodeficiency syndrome and disseminated histoplasmosis was higher in the second-generation assay. Physicians should be aware of the potential for false-positive results in sandwich immunoassays in specimens from patients who have received RATG.