Granular size segregation in silos with and without inserts.

The storage of granular materials is a critical process in industry, which has driven research into flow in silos. Varying material properties, such as particle size, can cause segregation of mixtures. This work seeks to elucidate the effects of size differences and determine how using a flow-correcting insert mitigates segregation during silo discharge. A rotating table was used to collect mustard seeds discharged from a three-dimensional (3D)-printed silo. This was loaded with bidisperse mixtures of varying proportions. A 3D-printed biconical insert was suspended near the hopper exit to assess its effect on the flow. Samples were analysed to determine the mass fractions of small particle species. The experiments without the insert resulted in patterns consistent with segregation. Introducing the insert into the silo eliminated the observed segregation during discharge. Discrete element method simulations of silo discharge were performed with and without the insert. These results mirrored the physical experiment and, when complimented with coarse graining analysis, explained the effect of the insert. Most of the segregation occurs at the grain-air free surface and is driven by large velocity gradients. In the silo with an insert, the velocity gradient at the free surface is greatly reduced, hence, so is the degree of segregation.

The dynamics of granular flow from a silo with two symmetric openings.

The dynamics of granular flow in a rectangular silo with two symmetrically placed exit openings is investigated using particle image velocimetry (PIV), flow rate measurements and discrete element modelling (DEM). The flow of mustard seeds in a Perspex silo is recorded using a high-speed camera and the resulting image frames are analysed using PIV to obtain velocity, velocity divergence and shear rate plots. A change in flow structure is observed as the distance L between the two openings is varied. The mass flow rate is shown to be at a maximum at zero opening separation, decreasing as L is increased; it then reaches a minimum before rising to an equilibrium rate close to two times that of an isolated (non-interacting) opening. The flow rate experiment is repeated using amaranth and screened sand and similar behaviour is observed. Although this result is in contrast with some recent DEM and physical experiments in silo systems, this effect has been reported in an analogous system: the evacuation of pedestrians from a room through two doors. Our experimental results are replicated using DEM and we show that inter-particle friction controls the flow rate behaviour and explains the discrepancies in the literature results.

Growth trajectories in early childhood, their relationship with antenatal and postnatal factors, and development of obesity by age 9 years: results from an Australian birth cohort study.

BACKGROUND: In an era where around one in four children in the United Kingdom, the United States, and Australia are overweight or obese, the development of obesity in early life needs to be better understood. We aimed to identify groups of children with distinct trajectories of growth in infancy and early childhood, to examine any association between these trajectories and body size at age 9, and to assess the relative influence of antenatal and postnatal exposures on growth trajectories. DESIGN: Prospective Australian birth cohort study. SUBJECTS AND METHODS: In total, 557 children with serial height and weight measurements from birth to 9 years were included in the study. Latent class growth models were used to derive distinct groups of growth trajectories from birth to age 3½ years. Multivariable logistic regression models were used to explore antenatal and postnatal predictors of growth trajectory groups, and multivariable linear and logistic regression models were used to examine the relationships between growth trajectory groups and body size at age 9 years. RESULTS: We identified four discrete growth trajectories from birth to age 3½ years, characterised as low, intermediate, high, or accelerating growth. Relative to the intermediate growth group, the low group had reduced z-body mass index (BMI) (-0.75 s.d.; 95% confidence interval (CI) -1.02, -0.47), and the high and accelerating groups were associated with increased body size at age 9 years (high: z-BMI 0.70 s.d.; 95% CI 0.49, 0.62; accelerating: z-BMI 1.64 s.d.; 95% CI 1.16, 2.11). Of the antenatal and postnatal exposures considered, the most important differentiating factor was maternal obesity in early pregnancy, associated with a near quadrupling of risk of membership of the accelerating growth trajectory group compared with the intermediate growth group (odds ratio (OR) 3.72; 95% CI 1.15, 12.05). CONCLUSIONS: Efforts to prevent childhood obesity may need to be embedded within population-wide strategies that also pay attention to healthy weight for women in their reproductive years.

Maggots as a wound debridement agent for chronic venous leg ulcers under graduated compression bandages: A randomised controlled trial.

OBJECTIVES: Slough in chronic venous leg ulcers may be associated with delayed healing. The purpose of this study was to assess larval debridement in chronic venous leg ulcers and to assess subsequent effect on healing. METHODS: All patients with chronic leg ulcers presenting to the leg ulcer service were evaluated for the study. Exclusion criteria were: ankle brachial pressure indices <0.85 or >1.25, no venous reflux on duplex and <20% of ulcer surface covered with slough. Participants were randomly allocated to either 4-layer compression bandaging alone or 4-layer compression bandaging + larvae. Surface areas of ulcer and slough were assessed on day 4; 4-layer compression bandaging was then continued and ulcer size was measured every 2 weeks for up to 12 weeks. RESULTS: A total of 601 patients with chronic leg ulcers were screened between November 2008 and July 2012. Of these, 20 were randomised to 4-layer compression bandaging and 20 to 4-layer compression bandaging + larvae. Median (range) ulcer size was 10.8 (3-21.3) cm(2) and 8.1 (4.3-13.5) cm(2) in the 4-layer compression bandaging and 4-layer compression bandaging + larvae groups, respectively (Mann-Whitney U test, P = 0.184). On day 4, median reduction in slough area was 3.7 cm(2) in the 4-layer compression bandaging group (P < 0.05) and 4.2 cm(2) (P < 0.001) in the 4-layer compression bandaging + larvae group. Median percentage area reduction of slough was 50% in the 4-layer compression bandaging group and 84% in the 4-layer compression bandaging + larvae group (Mann-Whitney U test, P < 0.05). The 12-week healing rate was 73% and 68% in the 4-layer compression bandaging and 4-layer compression bandaging + larvae groups, respectively (Kaplan-Meier analysis, P = 0.664). CONCLUSIONS: Larval debridement therapy improves wound debridement in chronic venous leg ulcers treated with multilayer compression bandages. However, no subsequent improvement in ulcer healing was demonstrated.

Growth in early life and the development of obesity by age 9 years: are there critical periods and a role for an early life stressor?

OBJECTIVE: Rapid growth, possibly occurring in critical periods in early life, may be important for the development of obesity. It is unknown whether this is influenced by postnatal exposures such as age-relevant sources of stress. Frequent house moves may be one such stressor. We aimed to examine if there is a period of growth in early life critical for the development of child obesity by age 9 years and assess the role of house moves in modifying any relationships between early life growth and obesity at age 9 years. DESIGN: Prospective Australian birth cohort study. SUBJECTS: In all, 392 children with serial body size measurements from birth to age 9 years. METHODS: Standardized body mass index (z-BMI) was available for six time points (spanning birth to 3½ years), and the total number of house moves between birth and 3½ years. The outcomes considered were z-BMI and % body fat (%BF) at age 9 years. Linear regression models were used to estimate the effects of serial measurements of z-BMI and number of house moves on the outcomes. RESULTS: Life-course plots showed that z-BMI at 3½ years was a statistically significant predictor of z-BMI at 9 years (ß=0.80; standard error (s.e.), 0.04), whereas z-BMI at 9 months (ß=-1.13; s.e., 0.40) and 3½ years (ß=4.82; s.e., 0.42) were significant predictors of %BF at age 9 years. There were statistically significant interactions between the number of house moves and change in z-BMI between 9 and 12 months, such that ≥ 3 house moves in early life amplified the detrimental effects of earlier rapid growth on both body size and composition at age 9 years. CONCLUSION: In the absence of evidence for a single critical period, efforts to prevent overweight and obesity are required throughout childhood. In addition, modifiable postnatal stressors may exacerbate effects of early growth on obesity in later childhood.

Changes in water quality of the River Frome (UK) from 1965 to 2009: is phosphorus mitigation finally working?

The water quality of the River Frome, Dorset, southern England, was monitored at weekly intervals from 1965 until 2009. Determinands included phosphorus, nitrogen, silicon, potassium, calcium, sodium, magnesium, pH, alkalinity and temperature. Nitrate-N concentrations increased from an annual average of 2.4 mg l⁻¹ in the mid to late 1960s to 6.0 mg l⁻¹ in 2008-2009, but the rate of increase was beginning to slow. Annual soluble reactive phosphorus (SRP) concentrations increased from 101 µg l⁻¹ in the mid 1960s to a maximum of 190 µg l⁻¹ in 1989. In 2002, there was a step reduction in SRP concentration (average=88 µg l⁻¹ in 2002-2005), with further improvement in 2007-2009 (average=49 µg l⁻¹), due to the introduction of phosphorus stripping at sewage treatment works. Phosphorus and nitrate concentrations showed clear annual cycles, related to the timing of inputs from the catchment, and within-stream bioaccumulation and release. Annual depressions in silicon concentration each spring (due to diatom proliferation) reached a maximum between 1980 and 1991, (the period of maximum SRP concentration) indicating that algal biomass had increased within the river. The timing of these silicon depressions was closely related to temperature. Excess carbon dioxide partial pressures (EpCO2) of 60 times atmospheric CO2 were also observed through the winter periods from 1980 to 1992, when phosphorus concentration was greatest, indicating very high respiration rates due to microbial decomposition of this enhanced biomass. Declining phosphorus concentrations since 2002 reduced productivity and algal biomass in the summer, and EpCO2 through the winter, indicating that sewage treatment improvements had improved riverine ecology. Algal blooms were limited by phosphorus, rather than silicon concentration. The value of long-term water quality data sets is discussed. The data from this monitoring programme are made freely available to the wider science community through the CEH data portal (http://gateway.ceh.ac.uk/).

Application of a semiautomated contour segmentation tool to identify the intervertebral nucleus pulposus in MR images.

BACKGROUND AND PURPOSE: Accurate identification of the NP in MR images is crucial to properly and objectively assess the intervertebral disk. Therefore, computerized segmentation of the NP in T2WI is necessary to produce repeatable and accurate results with minimal user input. MATERIAL AND METHODS: A semiautomated CS method was developed to identify the NP in T2WI on the basis of intensity differences compared with the AF. The method was validated by segmenting computer-generated images with a known ROI. The method was tested by using 63 MR images of rabbit lumbar disks, which were segmented to detect disk degeneration. An ICC was used to assess the repeatability of this method compared with manual segmentation. RESULTS: The error in the detected area of the rabbit NP by using CS was -3.49% ± 4.4% (mean ± SD) compared with 22.36% ± 5.55% by using manual segmentation. Moreover, the method was capable of detecting disk degeneration in a known rabbit puncture model of disk degeneration. Finally, this method had an ICC of 0.97 and 0.99 in regard to segmenting the area and calculating the MR imaging index of the NP, deeming it highly repeatable. CONCLUSIONS: The CS method is a semiautomated computer method able to segment the NP of the rabbit disk and detect disk degeneration. In addition, it could assist in clinical detection, assessment, and monitoring of early degeneration in human disks.

Evaluation of acid phosphatase as a confirmation test for Clostridium perfringens isolated from water.

AIMS: To evaluate testing for acid phosphatase as an alternative method for the confirmation of Clostridium perfringens isolated from water. METHODS AND RESULTS: Sixty-two reference strains of Clostridium were tested for their ability to produce acid phosphatase, as well as reduction of sulfite on tryptose sulfite cycloserine agar (TSC) and production of fluorescence in TSC supplemented with 4-methylumbelliferylphosphate (MUP). Additionally 155 environmental presumptive C. perfringens isolates from TSC incubated at 44 degrees C were identified and tested for acid phosphatase production and by the conventional MNLG (testing for motility, nitrate reduction, lactose fermentation and gelatin liquefaction) confirmation procedure. Twenty-seven strains from 15 species of Clostridium-reduced sulfite to some extent on TSC incubated at 44 degrees C, with a significant number of species being able to grow well at this temperature, indicating that a confirmation step is needed for the enumeration of C. perfringens on this medium. All 10 strains of C. perfringens tested, together with one strain each of Clostridium baratii and Clostridium rectum produced acid phosphatase. These also produced fluorescence on MUP supplemented TSC, as did 13 strains of acid phosphatase negative, sulfite-reducing clostridia, representing nine species. Of the environmental isolates, 114 were identified as C. perfringens of which 108 (94.7%) were confirmed by the acid phosphatase test compared with 104 (91.2%) by the MNLG tests. CONCLUSIONS: Testing for acid phosphatase production is at least as reliable, and much simpler to perform, than the current standard confirmation MNLG procedure. Incorporation of MUP into TSC does not reliably improve the identification of presumptive C. perfringens. SIGNIFICANCE AND IMPACT OF THE STUDY: Application of testing for acid phosphatase as a confirmation test for C. perfringens would substantially simplify the analysis for this bacterium from water samples, and reduce the analysis time to confirmed counts.

Guillain Barré syndrome precipitated by the use of antilymphocyte globulin in the treatment of severe aplastic anaemia.

This report describes the case of a 54 year old woman with very severe aplastic anaemia who was treated with antilymphocyte globulin (ALG) and developed Guillain Barré syndrome (GBS). No antecedent infective aetiology was identified. Although there are numerous reports of autoimmune disease after treatment with ALG in aplastic anaemia, and GBS after immunosuppressive treatment, there are none reporting GBS after the use of ALG for severe aplastic anaemia. The occurrence of autoimmune disease after immunosuppressive treatment, in particular ALG, is discussed, together with the possible mechanisms that result from T cell depression.

Prospective survey of factors affecting risk discussion during consent in a surgical specialty.

BACKGROUND: The Department of Health in the UK has developed new consent guidance but without clear recommendations on how the incidence and severity of a given risk should influence its discussion during the process of obtaining informed consent. Plastic surgery is a litigation-prone specialty that offers a paradigm for assessing attitudes to consent. METHODS: A questionnaire was sent to all surgeons at six plastic and reconstructive surgery units within the UK. It enquired what incidence of a relatively frequent minor severity risk such as wound infection, or an extremely rare but major risk such as stroke, would merit its discussion when obtaining informed consent for elective surgery. RESULTS: Sixty of 85 questionnaires were returned. For a minor risk, there was a consensus that an incidence threshold of 5 per cent or greater would necessitate its discussion. For a major risk, the modal threshold was 0.1 per cent, but there was a greater variability of response. CONCLUSION: There was a wide variation of opinion as to how frequently a major risk must occur before it is likely to be conveyed to a patient during the process of consent. The findings suggest that recent change in case law has yet to disseminate fully in one surgical specialty, with the potential for the challenge that consent is not 'informed'.

Molecular analysis of the microflora in chronic venous leg ulceration.

There is growing evidence to suggest that the resident microflora of chronic venous leg ulcers impairs cellular wound-healing responses, thereby playing an important role in maintaining the non-healing phenotype of many of these wounds. The significance of individual species of bacteria will remain unclear until it is possible to characterize fully the microflora of such lesions. The limitations and biases of culture-based microbiology are being realized and the subsequent application of molecular methods is revealing greater diversity within mixed bacterial populations than that demonstrated by culture alone. To date, this approach has been limited to a small number of systems, including the oral microflora. Here, for the first time, the comprehensive characterization of the microflora present in the tissue of a chronic venous leg ulcer is described by the comparison of 16S rDNA sequences amplified directly from the wound tissue with sequences obtained from bacteria that were isolated by culture. The molecular approach demonstrated significantly greater bacterial diversity than that revealed by culture. Furthermore, sequences were retrieved that may possibly represent novel species of bacteria. It is only by the comprehensive analysis of the wound microflora by both molecular and cultural methods that it will be possible to further our understanding of the role of bacteria in this important condition.

Anaerobic cocci populating the deep tissues of chronic wounds impair cellular wound healing responses in vitro.

BACKGROUND: Anaerobic cocci are estimated to be present in the deep tissues of over 50% of chronic skin wounds. While the part they play in the chronicity of these wounds is uninvestigated, anaerobic cocci have previously been shown to be involved in other chronic inflammatory human conditions. METHODS: In this study the anaerobic microflora of the deep tissues of 18 patients with refractory chronic venous leg ulcers (mean age 80.3 years; mean duration > 24 months) was characterized using strict anaerobic culture conditions. The effect of the anaerobic organisms isolated from these tissues on extracellular matrix (ECM) proteolysis and cellular wound healing responses was studied using in vitro models. RESULTS: Anaerobic organisms were present in the deep tissues of 14 of 18 wounds and were principally Peptostreptococcus spp. The effects of three Peptostreptococcus spp. isolated from these wounds (P. magnus, P. vaginalis and P. asaccharolyticus) on cellular wound healing responses were compared with those of two pathogenic organisms also isolated from these wounds (Pseudomonas aeruginosa and Citrobacter diversus). While the direct ECM proteolytic activity exhibited by the Peptostreptococcus spp. was limited, they did significantly inhibit both fibroblast and keratinocyte proliferation, but only at high concentrations. However, at lower concentrations peptostreptococcal supernatants profoundly inhibited keratinocyte wound repopulation and endothelial tubule formation. The magnitude of these effects varied between strains and they were distinct from those demonstrated by Pseudomonas aeruginosa and Citrobacter diversus. CONCLUSIONS: These studies confirm the importance of anaerobic organisms in chronic wounds and demonstrate an indirect, strain-specific mechanism by which these microorganisms may play a part in mediating the chronicity of these wounds.

Heterogeneity within the gram-positive anaerobic cocci demonstrated by analysis of 16S-23S intergenic ribosomal RNA polymorphisms.

Peptostreptococci are gram-positive, strictly anaerobic bacteria which, although regarded as members of the commensal human microflora, are also frequently isolated from sites of clinical infection. The study of this diverse group of opportunist pathogens has been hindered by an inadequate taxonomy and the lack of a valid identification scheme. Recent re-classification of the Peptostreptococcus family into five distinct genus groups has helped to clarify the situation. However, this has been on the basis of 16S rRNA sequence determinations, which are both time-consuming and expensive. The aim of the present study was to evaluate the use of PCR-amplified ribosomal DNA spacer polymorphisms for the rapid differentiation of the currently recognised taxa within the group of anaerobic gram-positive cocci. A collection comprising 19 reference strains with representatives of each of the 15 species, two close relatives and two of the well-characterised groups, together with 38 test strains was studied. All strains were identified to species group level by phenotypic means. Amplification of the 16S-23S intergenic spacer region (ISR) with universal primers produced distinct banding patterns for all the 19 reference strains and the patterns could be differentiated easily visually. However, of the 38 test strains, less than half could be speciated from ISR analysis alone. Only five groups produced correlating banding patterns for all members tested (Peptoniphilus lacrimalis, P. ivorii, Anaerococcus octavius, Peptostreptococcus anaerobius and Micromonas micros). For other species, either the type strain differed significantly from other species members (e.g., A. hydrogenalis) or there appeared to be considerable intra-species variation (e.g., A. vaginalis). Partial 16S rRNA gene sequences for the 'trisimilis' and 'betaGAL' groups showed that both are most closely related to the Anaerococcus group. This work highlights the heterogeneous nature of a number of Peptostreptococcus species and hence the need for still further revision of the taxonomy of this important group of pathogens.

Use of molecular techniques to study microbial diversity in the skin: chronic wounds reevaluated.

The skin is colonized by an array of microorganisms which form its natural microflora. Disruption to the normal barrier function of the skin (due to trauma or disease) may result in invasion of the dermis by opportunistic bacteria. To date, these organisms, which may contribute to the chronicity of skin wounds, have been analyzed solely by culture methods. It is increasingly realized that standard culture methods of analysis do not accurately reflect the full diversity of complex microflora. This review discusses the limitations of traditional culture approaches and reviews recent advances in molecular microbiological techniques which facilitate a more comprehensive characterization of the microflora within clinical samples. The currently available technologies and techniques are described, as is their use in clinical practice and their potential for diagnostic screening. Chronic venous ulceration of the lower limbs is an important skin disorder in which the microflora invading the dermal tissues contribute to the observed delayed healing. Using chronic leg ulcers as a working example, we show how strict culture and molecular microbiological techniques may be employed, for the first time in combination, to definitively characterize the invading microbial community of the dermis.

Multilocus sequence typing for characterization of methicillin-resistant and methicillin-susceptible clones of Staphylococcus aureus.

A multilocus sequence typing (MLST) scheme has been developed for Staphylococcus aureus. The sequences of internal fragments of seven housekeeping genes were obtained for 155 S. aureus isolates from patients with community-acquired and hospital-acquired invasive disease in the Oxford, United Kingdom, area. Fifty-three different allelic profiles were identified, and 17 of these were represented by at least two isolates. The MLST scheme was highly discriminatory and was validated by showing that pairs of isolates with the same allelic profile produced very similar SmaI restriction fragment patterns by pulsed-field gel electrophoresis. All 22 isolates with the most prevalent allelic profile were methicillin-resistant S. aureus (MRSA) isolates and had allelic profiles identical to that of a reference strain of the epidemic MRSA clone 16 (EMRSA-16). Four MRSA isolates that were identical in allelic profile to the other major epidemic MRSA clone prevalent in British hospitals (clone EMRSA-15) were also identified. The majority of isolates (81%) were methicillin-susceptible S. aureus (MSSA) isolates, and seven MSSA clones included five or more isolates. Three of the MSSA clones included at least five isolates from patients with community-acquired invasive disease and may represent virulent clones with an increased ability to cause disease in otherwise healthy individuals. The most prevalent MSSA clone (17 isolates) was very closely related to EMRSA-16, and the success of the latter clone at causing disease in hospitals may be due to its emergence from a virulent MSSA clone that was already a major cause of invasive disease in both the community and hospital settings. MLST provides an unambiguous method for assigning MRSA and MSSA isolates to known clones or assigning them as novel clones via the Internet.

Time course of motoneurone death after neonatal sciatic nerve crush in the rat.

Sciatic motoneurones were retrogradely labelled with long-lasting fluorescent dyes prior to unilateral nerve crush in either 3-day-old or adult rats. The number of surviving labelled motoneurones at intervals after nerve injury were compared to the number in the contralateral control ventral horn and in unoperated animals. Following adult nerve crush there was no significant reduction in the number of labelled motoneurones, but after neonatal nerve crush the count was reduced to about 35%. Most of the cell death occurred during the first 6 days after nerve injury, mainly from the lower half of the motor column, but about one third died between 6 and 12 days, mainly from the upper part. These results suggest that less mature motoneurones tend to die earliest, before the muscle is reinnervated. Those in the upper, more mature part of the motor pool survive longer but may still die during reinnervation. At least two types of glial cell were secondarily labelled by this method, distinguished by their response to nerve injury.

Cell-mediated immune response to Ross River virus in mice: evidence for a defective effector cell response.

Spleen cells recovered from mice during a primary infection with Ross River virus showed a virus-specific proliferative response when challenged in vitro. The majority of the proliferating cells were T-lymphocytes. In contrast, there was little detectable migration inhibition factor production by these spleen cells and little or no virus-specific cytotoxic activity. Sub-cutaneous challenge with virus elicited a weak delayed type hypersensitivity reaction.