Numerical simulation and validation of ocean waves measured by an Along-Track Interferometric Synthetic Aperture Radar

A new nonlinear integral transform of ocean wave spectra into Along-Track Interferometric Synthetic Aperture Radar (ATI-SAR) image spectra is described. ATI-SAR phase image spectra are calculated for various sea states and radar configurations based on the nonlinear integral transform. The numerical simulations show that the slant range to velocity ratio (R/V), significant wave height to ocean wavelength ratio (H-s/lambda), the baseline (2B) and incident angle (theta) affect ATI-SAR imaging. The ATI-SAR imaging theory is validated by means of Two X-band, HH-polarized ATI-SAR phase images of ocean waves and eight C-band, HH-polarized ATI-SAR phase image spectra of ocean waves. It is shown that ATI-SAR phase image spectra are in agreement with those calculated by forward mapping in situ directional wave spectra collected simultaneously with available ATI-SAR observations. ATI-SAR spectral correlation coefficients between observed and simulated are greater than 0.6 and are not sensitive to the degree of nonlinearity. However, the ATI-SAR phase image spectral turns towards the range direction, even if the real ocean wave direction is 30 degrees. It is also shown that the ATI-SAR imaging mechanism is significantly affected by the degree of velocity bunching nonlinearity, especially for high values of R/V and H-s/lambda.

Track displacement and energy loss in a railway embankment

The mainline railway track between Dublin and Belfast was constructed during the 1850s, with substantial lengths of railway embankment constructed over soft, peaty soils. In recent years Northern Ireland Railways (NIR) has noticed that the sections of the railway track constructed on these peaty soils have been deteriorating at an increasing rate. Train speeds have been reduced in response to concerns that cyclic track displacements appear to be increasing over time in response to train loading. Track maintenance has also increased significantly. The research described in this paper was undertaken to quantify the response to cyclic train loading of two portions of this track founded on peaty soils. Track displacements were recorded using a sensor system specifically created for this project. The sensor consisted of a photosensitive array, mounted on the sleepers, and a laser, which was targeted onto the photosensitive array from a location outside the area of influence of train loading. Track deflections from 5 to 20 mm were measured under train speeds from near zero to over 120 km/h. The temporal variation in track displacement was used to calibrate an analytical (Winkler) model. This analysis suggests that the deformation of the embankment under train loading was not due to dynamic excitation but rather to static deformation of the poor-quality fill and soft foundation materials. As a consequence, the analytical model highlighted that train speed has limited effect on the magnitude of the deflection of the embankment within NIR operating speeds, but has the potential to significantly reduce the power lost to the damping within the embankment and subgrade.

Xenopus cytoplasmic linker-associated protein 1 (XCLASP1) promotes axon elongation and advance of pioneer microtubules

Dynamic microtubules (MTs) are required for neuronal guidance, in which axons extend directionally toward their target tissues. We found that depletion of the MT-binding protein Xenopus cytoplasmic linker-associated protein 1 (XCLASP1) or treatment with the MT drug Taxol reduced axon outgrowth in spinal cord neurons. To quantify the dynamic distribution of MTs in axons, we developed an automated algorithm to detect and track MT plus ends that have been fluorescently labeled by end-binding protein 3 (EB3). XCLASP1 depletion reduced MT advance rates in neuronal growth cones, very much like treatment with Taxol, demonstrating a potential link between MT dynamics in the growth cone and axon extension. Automatic tracking of EB3 comets in different compartments revealed that MTs increasingly slowed as they passed from the axon shaft into the growth cone and filopodia. We used speckle microscopy to demonstrate that MTs experience retrograde flow at the leading edge. Microtubule advance in growth cone and filopodia was strongly reduced in XCLASP1-depleted axons as compared with control axons, but actin retrograde flow remained unchanged. Instead, we found that XCLASP1-depleted growth cones lacked lamellipodial actin organization characteristic of protrusion. Lamellipodial architecture depended on XCLASP1 and its capacity to associate with MTs, highlighting the importance of XCLASP1 in actin-microtubule interactions.

Killer immunoglobulin-like Receptors (KIR) haplogroups A and B track with Natural Killer Cells and Cytokine Profile in Aged Subjects: Observations from Octo/Nonagenarians in the Belfast Elderly Longitudinal Free-living Aging STudy (BELFAST)

Background: Natural Killer Cells (NK) play an important role in detection and elimination of virus-infected, damaged or cancer cells. NK cell function is guided by expression of Killer Immunoglobulin-like Receptors (KIRs) and contributed to by the cytokine milieu. KIR molecules are grouped on NK cells into stimulatory and inhibitory KIR haplotypes A and B, through which NKs sense and tolerate HLA self-antigens or up-regulate the NK-cytotoxic response to cells with altered HLA self-antigens, damaged by viruses or tumours. We have previously described increased numbers of NK and NK-related subsets in association with sIL-2R cytokine serum levels in BELFAST octo/nonagenarians. We hypothesised that changes in KIR A and B haplotype gene frequencies could explain the increased cytokine profiles and NK compartments previously described in Belfast Elderly Longitudinal Free-living Aging STudy (BELFAST) octo/nonagenarians, who show evidence of ageing well.

Results: In the BELFAST study, 24% of octo/nonagenarians carried the KIR A haplotype and 76% KIR B haplotype with no differences for KIR A haplogroup frequency between male or female subjects (23% v 24%; p=0.88) or for KIR B haplogroup (77% v 76%; p=0.99). Octo/nonagenarian KIR A haplotype carriers showed increased NK numbers and percentage compared to Group B KIR subjects (p=0.003; p=0.016 respectively). There were no KIR A/ B haplogroup-associated changes for related CD57+CD8 (high or low) subsets. Using logistic regression, KIR B carriers were predicted to have higher IL-12 cytokine levels compared to KIR A carriers by about 3% (OR 1.03, confidence limits CI 0.99–1.09; p=0.027) and 14% higher levels for TGF-ß (active), a cytokine with an anti-inflammatory role, (OR 1.14, confidence limits CI 0.99–1.09; p=0.002).

Conclusion: In this observational study, BELFAST octo/nonagenarians carrying KIR A haplotype showed higher NK cell numbers and percentage compared to KIR B carriers. Conversely, KIR B haplotype carriers, with genes encoding for activating KIRs, showed a tendency for higher serum pro-inflammatory cytokines compared to KIR A carriers. While the findings in this study should be considered exploratory they may serve to stimulate debate about the immune signatures of those who appear to age slowly and who represent a model for good quality survivor-hood.© 2013 Rea et al.; licensee BioMed Central Ltd.

Multimodal functional and anatomical imaging identifies preclinical microvascular abnormalities in type 1 diabetes mellitus

Structural and functional change in the microcirculation in type 1 diabetes mellitus predicts future end-organ damage and macrovascular events. We explored the utility of novel signal processing techniques to detect and track change in ocular hemodynamics in patients with this disease. 24 patients with uncomplicated type 1 diabetes mellitus, and 18 age-and-sex matched control subjects were studied. Doppler ultrasound was used to interrogate the carotid and ophthalmic arteries and digital photography to image the retinal vasculature. Frequency analysis algorithms were applied to quantify velocity waveform structure and retinal photographic data at baseline and following inhalation of 100% oxygen. Frequency data was compared between groups. No significant differences were found in the resistive index between groups at baseline or following inhaled oxygen. Frequency analysis of the Doppler flow velocity waveforms identified significant differences in bands 3-7 between patients and controls in data captured from the ophthalmic artery (p<0.01 for each band). In response to inhaled oxygen, changes in the frequency band amplitudes were significantly greater in control subjects compared with patients (p<0.05). Only control subjects demonstrated a positive correlation (R=0.61) between change in retinal vessel diameter and frequency band amplitudes derived from ophthalmic artery waveform data. The use of multimodal signal processing techniques applied to Doppler flow velocity waveforms and retinal photographic data identified preclinical change in the ocular microcirculation in patients with uncomplicated diabetes mellitus. An impaired autoregulatory response of the retinal microvasculature may contribute to the future development of retinopathy in such patients.

A realistic evaluation of track and trigger systems and acute care training for early recognition and treatment of deteriorating ward-based patients: research protocol.

Aim The aim of the study is to evaluate factors that enable or constrain the implementation and service delivery of early warnings systems or acute care training in practice. Background To date there is limited evidence to support the effectiveness of acute care initiatives (early warning systems, acute care training, outreach) in reducing the number of adverse events (cardiac arrest, death, unanticipated Intensive Care admission) through increased recognition and management of deteriorating ward based patients in hospital [1-3]. The reasons posited are that previous research primarily focused on measuring patient outcomes following the implementation of an intervention or programme without considering the social factors (the organisation, the people, external influences) which may have affected the process of implementation and hence measured end-points. Further research which considers the social processes is required in order to understand why a programme works, or does not work, in particular circumstances [4]. Method The design is a multiple case study approach of four general wards in two acute hospitals where Early Warning Systems (EWS) and Acute Life-threatening Events Recognition and Treatment (ALERT) course have been implemented. Various methods are being used to collect data about individual capacities, interpersonal relationships and institutional balance and infrastructures in order to understand the intended and unintended process outcomes of implementing EWS and ALERT in practice. This information will be gathered from individual and focus group interviews with key participants (ALERT facilitators, nursing and medical ALERT instructors, ward managers, doctors, ward nurses and health care assistants from each hospital); non-participant observation of ward organisation and structure; audit of patients' EWS charts and audit of the medical notes of patients who deteriorated during the study period to ascertain whether ALERT principles were followed. Discussion & progress to date This study commenced in January 2007. Ethical approval has been granted and data collection is ongoing with interviews being conducted with key stakeholders. The findings from this study will provide evidence for policy-makers to make informed decisions regarding the direction for strategic and service planning of acute care services to improve the level of care provided to acutely ill patients in hospital. References 1. Esmonde L, McDonnell A, Ball C, Waskett C, Morgan R, Rashidain A et al. Investigating the effectiveness of Critical Care Outreach Services: A systematic review. Intensive Care Medicine 2006; 32: 1713-1721 2. McGaughey J, Alderdice F, Fowler R, Kapila A, Mayhew A, Moutray M. Outreach and Early Warning Systems for the prevention of Intensive Care admission and death of critically ill patients on general hospital wards. Cochrane Database of Systematic Reviews 2007, Issue 3. www.thecochranelibrary.com 3. Winters BD, Pham JC, Hunt EA, Guallar E, Berenholtz S, Pronovost PJ (2007) Rapid Response Systems: A systematic review. Critical Care Medicine 2007; 35 (5): 1238-43 4. Pawson R and Tilley N. Realistic Evaluation. London; Sage: 1997

Organizational commitment and perceived relatedness as correlates of the intention to continue officiating in track and field

The objectives of the present study were to explore three components of organizational commitment (affective [AC], normative [NC] and continuance [CC] commitment; Allen & Meyer, 1991), perceived relatedness (Oeci & Ryan, 1985; 2002), and behavioural intention (Ajzen, 2002) within the context of volunteer track and field officiating. The objectives were examined in a 2-phase study. Ouring phase 1, experts (N = 10) with domain familiarity assessed the item content relevance and representation of modified organizational commitment (OC; Meyer, Allen & Smith, 1993) and perceived relatedness (La Guardia, Oeci, Ryan & Couchman, 2000) items. Fourteen of 26 (p < .05) items were relevant (Aiken's coefficient V) and NC (M = 3.88, SO = .64), CC (M = 3.63, SD = .52), and relatedness (M = 4.00, SD = .93) items had mean item content-representation ratings of either "good" or "very good" while AC (M = 2.50, SD = 0.58) was rated "fair". Participants in phase 2 (N = 80) responded to items measuring demographic variables, perceptions of OC to Athletics Canada, perceived relatedness to other track and field officials, and a measure of intention (yiu, Au & Tang, 2001) to continue officiating. Internal consistency reliability estimates (Cronbach's (1951) coefficient alpha) were as follows: (a) AC = .78, (b) CC = .85, (c) NC = .80 (d) perceived relatedness = .70 and, (e) intention = .92 in the present sample. Results suggest that the track and field officials felt only minimally committed to Athletics Canada (AC M = 3.90, SD = 1.23; NC M = 2.47, SD = 1.25; CC M = 3.32; SD = 1.34) and that their relationships with other track and field officials were strongly endorsed (M = 5.86, SD = 0.74). Bivariate correlations (Pearson r) indicated that perceived relatedness to other track and field officials demonstrated the strongest relationship with intention to continue officiating (r = .346, p < .05), while dimensions of OC were not significantly related to intention (all p's > .05). Together perceived relatedness (j3 = .339, p = .004), affective commitment (j3 = -.1 53, p = .308), normative commitment (j3 = -.024, p = .864) and continuance commitment (j3 = .186, P = .287) contribute to the prediction of intention to continued officiating (K = .139). These relationships remained unaffected by the inclusion of demographic (j3age = -.02; P years with Athletics Canada = -.13; bothp's > .05) or alternative commitment (j3sport = -.19; P role = .15; Pathletes = .20; all p' s > .05) considerations. Three open-ended questions elicited qualitative responses regarding participants' reasons for officiating. Responses reflecting initial reasons for officiating formed these higher order themes: convenience, helping reasons, extension of role, and intrinsic reasons. Responses reflecting reasons for continuing to officiate formed these higher order themes: track and field, to help, and personal benefits. Responses reflecting changes that would influence continued involvement were: political, organizational/structural, and personal. These results corroborate the findings of previous investigations which state that the reasons underpinning volunteer motivations change over time (Cuskelly et al., 2002). Overall, the results of this study suggest that track and field officials feel minimal commitment to the organization of Athletics Canada but a stronger bond with their fellow officials. Moreover, the degree to which track and field officials feel meaningfully connected to one another appears to exert a positive influence on their intentions to continue officiating. As such, it is suggested that in order to promote continued involvement, Athletics Canada increases its focus on fostering environments promoting positive interactions among officials.

Dexmedetomidina vs Remifentanil en fast track (transito rápido) durante cirugía cardiaca

Actualmente las técnicas de anestesia de tránsito rápido en cirugía cardiaca se basan en la utilización de remifentanil, sin embargo este al tener una vida media tan corta hace que sea necesaria la utilización de opioides durante el posoperatorio inmediato presentandose el riesgo de depresión ventilatoria, y complicaciones respiratorias, es por esto que la dexmedetomidina podría ser una opción bastante atractiva debida a que no produce depresión de los centros respiratorios, y disminuye el consumo de opioides en el postoperatorio hasta un 66%. Previa aprobación del comité de ética se realizó un estudio clínico controlado y aleatorizado en dos grupos de 20 pacientes, El primer grupo recibió inducción con propofol 2mg/Kg, pancuronio 0.8mg/kg, y fentanil 2mcg/kg seguido de un bolo de dexmedetomidina de 0.5mcg/kg y una infusión de 0.3 - 0.7 mcg/kg/h la cual fue suspendida al finalizar la colocación de los alambres esternales, el grupo de remifentanil recibió una inducción con propofol y pancuronio a las mismas dosis, seguido de una infusión de remifentanil de 0.1 - 0.5 mcg/kg/min suspendida al finalizar el cierre de la piel, ambos grupos recibieron analgesia con dipirona 50mg/kg, morfina 0.1mg/kg seguida de dosis de rescate de 3mg según necesidad, e infiltración de la herida quirurgica con 40cc de Bupivacaina al 0.25%. Se midio el tiempo y lugar de extubación, el consumo de medicamentos vasopresores y vasodilatadores durante la cirugiaasi como el consumo de morfina el VAS y la incidencia de nausea y vomito durante las primeras 24h posoperatorias. El 85% de los pacientes fueron extubados en salas de cirugia, sin encontrarse diferencias estadiscamente significativas entre los tiempos de extubación de ambos grupos (11.7min) para remifentanil, y (9.6min) para dexmedetomidina, en cuanto al consumo de morfina este fue significativamente menor en el grupo de dexmedetomidina 4mg vs 15mg en el grupo de remifentanil así como también lo fue la incidencia de nausea y vomito 42.9% remifentanil vs 5.2% dexmedetomidina p:0.00009. A nuestro saber este es el primer estudio clínico en la literatura en el cual se ha propuesto a la dexmedetomidina como una alternativa para técnicas anestésicas de transito rápido en cirugia cardiaca. Los resultados sugieren que es tan eficaz como el remifentanil para permitir la extubación temprana de este grupo de pacientes con una menor consumo de morfina y una menor incidencia de nauseas y vomito durante el posoperatorio. Se recomiendan la realización de estudios adicionales que permitan ratificar los resultados previamente encontrados.

The Storm-Track Response to Idealized SST Perturbations in an Aquaplanet GCM

The tropospheric response to midlatitude SST anomalies has been investigated through a series of aquaplanet simulations using a high-resolution version of the Hadley Centre atmosphere model (HadAM3) under perpetual equinox conditions. Model integrations show that increases in the midlatitude SST gradient generally lead to stronger storm tracks that are shifted slightly poleward, consistent with changes in the lower-tropospheric baroclinicity. The large-scale atmospheric response is, however, highly sensitive to the position of the SST gradient anomaly relative to that of the subtropical jet in the unperturbed atmosphere. In particular, when SST gradients are increased very close to the subtropical jet, then the Hadley cell and subtropical jet is strengthened while the storm track and eddy-driven jet are shifted equatorward. Conversely, if the subtropical SST gradients are reduced and the midlatitude gradients increased, then the storm track shows a strong poleward shift and a well-separated eddy-driven jet is produced. The sign of the SST anomaly is shown to play a secondary role in determining the overall tropospheric response. These findings are used to provide a new and consistent interpretation of some previous GCM studies concerning the atmospheric response to midlatitude SST anomalies.

The basic ingredients of the North Atlantic storm track. Part I: land-sea contrast and orography

Understanding and predicting changes in storm tracks over longer time scales is a challenging problem, particularly in the North Atlantic. This is due in part to the complex range of forcings (land–sea contrast, orography, sea surface temperatures, etc.) that combine to produce the structure of the storm track. The impact of land–sea contrast and midlatitude orography on the North Atlantic storm track is investigated through a hierarchy of GCM simulations using idealized and “semirealistic” boundary conditions in a high-resolution version of the Hadley Centre atmosphere model (HadAM3). This framework captures the large-scale essence of features such as the North and South American continents, Eurasia, and the Rocky Mountains, enabling the results to be applied more directly to realistic modeling situations than was possible with previous idealized studies. The physical processes by which the forcing mechanisms impact the large-scale flow and the midlatitude storm tracks are discussed. The characteristics of the North American continent are found to be very important in generating the structure of the North Atlantic storm track. In particular, the southwest–northeast tilt in the upper tropospheric jet produced by southward deflection of the westerly flow incident on the Rocky Mountains leads to enhanced storm development along an axis close to that of the continent’s eastern coastline. The approximately triangular shape of North America also enables a cold pool of air to develop in the northeast, intensifying the surface temperature contrast across the eastern coastline, consistent with further enhancements of baroclinicity and storm growth along the same axis.