Oculometric parameters of hyperopia in children with esotropic amblyopia

Purpose: To study the oculometric parameters of hyperopia in children with esotropic amblyopia, comparing amblyopic eyes with fellow eyes. Methods: Thirty-seven patients (5-8 years old) with bilateral hyperopia and esotropic amblyopia underwent a comprehensive ophthalmic examination, including cycloplegic refraction, keratometry and A-scan ultrasonography. Anterior chamber depth, lens thickness, vitreous chamber depth and total axial length were recorded. The refractive power of the crystalline lens was calculated using Bennett`s equations. Paired Student`s t-tests were used to compare ocular biometric measurements between amblyopic eyes and their fellow eyes. The associations of biometric parameters with refractive errors were assessed using Pearson correlation coefficients and linear regression. Multivariable models including axial length, corneal power and lens power were also constructed. Results: Amblyopic eyes were found to have significantly more hyperopic refraction, less corneal power, greater lens power, shorter vitreous chamber depth and shorter axial length, despite similar anterior chamber depth and lens thickness. The strongest correlation with refractive error was observed for the axial length/corneal radius ratio (r(36) = -0.92, p < 0.001 for amblyopic and r(36) = 0.87, p < 0.001 for fellow eyes). Axial length accounted for 39.2% (R(2)) of the refractive error variance in amblyopic eyes and 35.5% in fellow eyes. Adding corneal power to the model increased R(2) to 85.7% and 79.6%, respectively. A statistically significant correlation was found between axial length and corneal power, indicating decreasing corneal power with increasing axial length, and they were similar for amblyopic eyes (r(36) = 0.53,p < 0.001) and fellow eyes (r(36) = -0.57, p < 0.001). A statistically significant correlation was also found between axial length and lens power, indicating decreasing lens power with increasing axial length (r(36) = -0.72, p < 0.001 for amblyopic eyes and r(36) = -0.69, p < 0.001 for fellow eyes). Conclusions: We observed that the correlation among the major oculometric parameters and their individual contribution to hyperopia in esotropic children were similar in amblyopic and non-amblyopic eyes. This finding suggests that the counterbalancing effect of greater corneal and lens power associated with shorter axial length is similar in both eyes of patients with esotropic amblyopia.

Physiologic parameters that affect pulse transit time difference between the upper and lower limbs in children

Pulse wave velocity (PWV) is a known parameter that is related to arterial distensibility. However, its potential is hampered by the absence of appropriate techniques to estimate it noninvasively. PWV can be used as an assessment of increased arterial stiffness that is linked to systolic hypertension, excess cardiovascular morbidity and mortality.(1,2)

A comparison of methods to identify open-lung PEEP

Purpose: Many methods exist in the literature for identifying PEEP to set in ARDS patients following a lung recruitment maneuver (RM). We compared ten published parameters for setting PEEP following a RM. Methods: Lung injury was induced by bilateral lung lavage in 14 female Dorset sheep, yielding a PaO(2) 100-150 mmHg at F(I)O(2) 1.0 and PEEP 5 cmH(2)O. A quasi-static P-V curve was then performed using the supersyringe method; PEEP was set to 20 cmH(2)O and a RM performed with pressure control ventilation (inspiratory pressure set to 40-50 cmH(2)O), until PaO(2) + PaCO(2) > 400 mmHg. Following the RM, a decremental PEEP trial was performed. The PEEP was decreased in 1 cmH(2)O steps every 5 min until 15 cmH(2)O was reached. Parameters measured during the decremental PEEP trial were compared with parameters obtained from the P-V curve. Results: For setting PEEP, maximum dynamic tidal respiratory compliance, maximum PaO(2), maximum PaO(2) + PaCO(2), and minimum shunt calculated during the decremental PEEP trial, and the lower Pflex and point of maximal compliance increase on the inflation limb of the P-V curve (Pmci,i) were statistically indistinguishable. The PEEP value obtained using the deflation upper Pflex and the point of maximal compliance decrease on the deflation limb were significantly higher, and the true inflection point on the inflation limb and minimum PaCO(2) were significantly lower than the other variables. Conclusion: In this animal model of ARDS, dynamic tidal respiratory compliance, maximum PaO(2), maximum PaO(2) + PaCO(2), minimum shunt, inflation lower Pflex and Pmci,i yield similar values for PEEP following a recruitment maneuver.

Application of biotechnology in breeding lentil for resistance to biotic and abiotic stress

Lentil is a self-pollinating diploid (2n = 14 chromosomes) annual cool season legume crop that is produced throughout the world and is highly valued as a high protein food. Several abiotic stresses are important to lentil yields world wide and include drought, heat, salt susceptibility and iron deficiency. The biotic stresses are numerous and include: susceptibility to Ascochyta blight, caused by Ascochyta lentis; Anthracnose, caused by Colletotrichum truncatum; Fusarium wilt, caused by Fusarium oxysporum; Sclerotinia white mold, caused by Sclerotinia sclerotiorum; rust, caused by Uromyces fabae; and numerous aphid transmitted viruses. Lentil is also highly susceptible to several species of Orabanche prevalent in the Mediterranean region, for which there does not appear to be much resistance in the germplasm. Plant breeders and geneticists have addressed these stresses by identifying resistant/tolerant germplasm, determining the genetics involved and the genetic map positions of the resistant genes. To this end progress has been made in mapping the lentil genome and several genetic maps are available that eventually will lead to the development of a consensus map for lentil. Marker density has been limited in the published genetic maps and there is a distinct lack of co-dominant markers that would facilitate comparisons of the available genetic maps and efficient identification of markers closely linked to genes of interest. Molecular breeding of lentil for disease resistance genes using marker assisted selection, particularly for resistance to Ascochyta blight and Anthracnose, is underway in Australia and Canada and promising results have been obtained. Comparative genomics and synteny analyses with closely related legumes promises to further advance the knowledge of the lentil genome and provide lentil breeders with additional genes and selectable markers for use in marker assisted selection. Genomic tools such as macro and micro arrays, reverse genetics and genetic transformation are emerging technologies that may eventually be available for use in lentil crop improvement.

Dynamic strain measurement using piezoelectric polymer film

Piezoelectric polymers have been used to form the basis of dynamic strain gauges for the detection of stress waves. The linearity of response was tested using a split Hopkinson pressure bar arrangement. The results obtained illustrate the effectiveness of piezoelectric film strain gauges in the measurement of axial stress waves.

Skeletal Microstructural Abnormalities in Postmenopausal Women With Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is associated with osteoporosis and fragility fractures. The objectives of this study were to assess static and dynamic indices of cancellous and cortical bone structure in postmenopausal women with COPD. Twenty women with COPD who had not received chronic oral glucocorticoids underwent bone biopsies after double tetracycline labeling. Biopsies were analyzed by histomorphometry and mu CT and compared with age-matched controls. Distribution of the patients according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) was: Type I (15%), Type II (40%), Type III (30%), and Type IV (15%). Mean (+/-SD) cancellous bone volume (15.20 +/- 5.91 versus 21.34 +/- 5.53%, p = .01), trabecular number (1.31 +/- 0.26 versus 1.77 +/- 0.51/mm, p = .003), and trabecular thickness (141 +/- 23 versus 174 +/- 36 mu m, p = .006) were lower in patients than in controls. Connectivity density was lower in COPD (5.56 +/- 2.78 versus 7.94 +/- 3.08 mu m, p = .04), and correlated negatively with smoking (r = -0.67; p = .0005). Trabecular separation (785 +/- 183 versus 614 +/- 136 mu m, p = .01) and cortical porosity (4.11 +/- 1.02 versus 2.32 +/- 0.94 voids/mm(2); p < .0001) were higher in COPD while cortical width (458 +/- 214 versus 762 +/- 240 mu m; p < .0001) was lower. Dynamic parameters showed significantly lower mineral apposition rate in COPD (0.56 +/- 0.16 versus 0.66 +/- 0.12 mu m/day; p = .01). Patients with more severe disease, GOLD III and IV, presented lower bone formation rate than GOLDI and II (0.028 +/- 0.009 versus 0.016 +/- 0.011 mu m(3)/mu m(2)/day;p = 04). This is the first evaluation of bone microstructure and remodeling in COPD. The skeletal abnormalities seen in cancellous and cortical bone provide an explanation for the high prevalence of vertebral fractures in this disease. (C) 2010 American Society for Bone and Mineral Research.

Diel vertical migration: Modelling light-mediated mechanisms

Light is generally regarded as the most likely cue used by zooplankton to regulate their vertical movements through the water column. However, the way in which light is used by zooplankton as a cue is not well understood. In this paper we present a mathematical model of diel vertical migration which produces vertical distributions of zooplankton that vary in space and time. The model is used to predict the patterns of vertical distribution which result when animals are assumed to adopt one of three commonly proposed mechanisms for vertical swimming. First, we assume zooplankton tend to swim towards a preferred intensity of light. We then assume zooplankton swim in response to either the rate of change in light intensity or the relative rate of change in light intensity. The model predicts that for all three mechanisms movement is fastest at sunset and sunrise and populations are primarily influenced by eddy diffusion at night in the absence of a light stimulus. Daytime patterns of vertical distribution differ between the three mechanisms and the reasons for the predicted differences are discussed. Swimming responses to properties of the light field are shown to be adequate for describing diel vertical migration where animals congregate in near surface waters during the evening and reside at deeper depths during the day. However, the model is unable to explain how some populations halt their ascent before reaching surface waters or how populations re-congregate in surface waters a few hours before sunrise, a phenomenon which is sometimes observed in the held. The model results indicate that other exogenous or endogenous factors besides light may play important roles in regulating vertical movement.

Arterial pulse pressure variation predicting fluid responsiveness in critically ill patients (Retracted article. See vol. 31, pg. 542, 2009)

In critically ill patients, it is important to predict which patients will have their systemic blood flow increased in response to volume expansion to avoid undesired hypovolemia and fluid overloading. Static parameters such as the central venous pressure, the pulmonary arterial occlusion pressure, and the left ventricular end-diastolic dimension cannot accurately discriminate between responders and nonresponders to a fluid challenge. In this regard, respiratory-induced changes in arterial pulse pressure have been demonstrated to accurately predict preload responsiveness in mechanically ventilated patients. Some experimental and clinical studies confirm the usefulness of arterial pulse pressure as a useful tool to guide fluid therapy in critically ill patients.

Analysis of dynamic process models for structural insight and model reduction .1. Structural identification measures

An important consideration in the development of mathematical models for dynamic simulation, is the identification of the appropriate mathematical structure. By building models with an efficient structure which is devoid of redundancy, it is possible to create simple, accurate and functional models. This leads not only to efficient simulation, but to a deeper understanding of the important dynamic relationships within the process. In this paper, a method is proposed for systematic model development for startup and shutdown simulation which is based on the identification of the essential process structure. The key tool in this analysis is the method of nonlinear perturbations for structural identification and model reduction. Starting from a detailed mathematical process description both singular and regular structural perturbations are detected. These techniques are then used to give insight into the system structure and where appropriate to eliminate superfluous model equations or reduce them to other forms. This process retains the ability to interpret the reduced order model in terms of the physico-chemical phenomena. Using this model reduction technique it is possible to attribute observable dynamics to particular unit operations within the process. This relationship then highlights the unit operations which must be accurately modelled in order to develop a robust plant model. The technique generates detailed insight into the dynamic structure of the models providing a basis for system re-design and dynamic analysis. The technique is illustrated on the modelling for an evaporator startup. Copyright (C) 1996 Elsevier Science Ltd

Analysis of dynamic models for structural insight and model reduction .2. A multi-stage compressor shutdown case-study

In this second paper, the three structural measures which have been developed are used in the modelling of a three stage centrifugal synthesis gas compressor. The goal of this case study is to determine the essential mathematical structure which must be incorporated into the compressor model to accurately model the shutdown of this system. A simple, accurate and functional model of the system is created via three structural measures. It was found that the model can be correctly reduced into its basic modes and that the order of the differential system can be reduced from 51(st) to 20(th). Of the 31 differential equational 21 reduce to algebraic relations, 8 become constants and 2 can be deleted thereby increasing the algebraic set from 70 to 91 equations. An interpretation is also obtained as to which physical phenomena are dominating the dynamics of the compressor add whether the compressor will enter surge during the shutdown. Comparisons of the reduced model performance against the full model are given, showing the accuracy and applicability of the approach. Copyright (C) 1996 Elsevier Science Ltd

A Comparison Between Pulse Pressure Variation and Right End Diastolic Volume Index as Guides to Resuscitation in a Model of Hemorrhagic Shock in Pigs

Background: Different hemodynamic parameters including static indicators of cardiac preload as right ventricular end-diastolic volume index (RVEDVI) and dynamic parameters as pulse pressure variation (PPV) have been used in the decision-making process regarding volume expansion in critically ill patients. The objective of this study was to compare fluid resuscitation guided by either PPV or RVEDVI after experimentally induced hemorrhagic shock. Methods: Twenty-six anesthetized and mechanically ventilated pigs were allocated into control (group I), PPV (group II), or RVEDVI (group III) group. Hemorrhagic shock was induced by blood withdrawal to target mean arterial pressure of 40 mm Hg, maintained for 60 minutes. Parameters were measured at baseline, time of shock, 60 minutes after shock, immediately after resuscitation with hydroxyethyl starch 6% (130/0.4), 1 hour and 2 hours thereafter. The endpoint of fluid resuscitation was determined as the baseline values of PPV and RVEDVI. Statistical analysis of data was based on analysis of variance for repeated measures followed by the Bonferroni test (p < 0.05). Results: Volume and time to resuscitation were higher in group III than in group II (group III = 1,305 +/- 331 mL and group II = 965 +/- 245 mL, p < 0.05; and group III = 24.8 +/- 4.7 minutes and group II = 8.8 +/- 1.3 minutes, p < 0.05, respectively). All static and dynamic parameters and biomarkers of tissue oxygenation were affected by hemorrhagic shock and nearly all parameters were restored after resuscitation in both groups. Conclusion: In the proposed model of hemorrhagic shock, resuscitation to the established endpoints was achieved within a smaller amount of time and with less volume when guided by PPV than when guided by pulmonary artery catheter-derived RVEDVI.

Voiding Dysfunction in Patients With Parkinson`s Disease: Impact of Neurological Impairment and Clinical Parameters

Aims: We assessed the lower urinary tract symptoms (LUTS) of patients with Parkinson`s disease (PD) and their association with different clinical parameters. Methods: We prospectively evaluated 110 patients (84 men), with a mean age of 61.8 +/- 9.6 years. Mean duration of the disease was 12.3 +/- 7.2 years. Neurological impairment was assessed by the Hoehn-Yahr and the Unified Parkinson Disease Rating scales. LUTS were assessed by the International Continence Society questionnaire. We evaluated the impact of age, PD duration, neurological impairment, gender, and use of anti-Parkinsonian drugs on the voiding function. Results: On multivariate analysis, voiding dysfunction increased with the neurological impairment, but not with patient`s age or disease duration. Quality of life (QOL) was affected by the severity of LUTS, and the symptoms with the worst impact were frequency and nocturia. Sixty-three (57.2%) patients were symptomatic. They did not differ with the asymptomatic as to age and disease duration, but had more severe neurological impairment. No impact on LUTS was associated with the use of levodopa, anticholinergics, and dopamine receptor agonists. Men and women were similarly affected by urinary symptoms. Conclusions: The severity of the neurological disease is the only predictive factor for the occurrence of voiding dysfunction, which affects men and women alike. Neztrourol. Urodynam. 28.510-515, 2009. (C) 2009 Wiley-Liss, Inc.

A Dynamic Model of Hand-and-Foot Syndrome in Patients Receiving Capecitabine

For the purpose of developing a longitudinal model to predict hand-and-foot syndrome (HFS) dynamics in patients receiving capecitabine, data from two large phase III studies were used. Of 595 patients in the capecitabine arms, 400 patients were randomly selected to build the model, and the other 195 were assigned for model validation. A score for risk of developing HFS was modeled using the proportional odds model, a sigmoidal maximum effect model driven by capecitabine accumulation as estimated through a kinetic-pharmacodynamic model and a Markov process. The lower the calculated creatinine clearance value at inclusion, the higher was the risk of HFS. Model validation was performed by visual and statistical predictive checks. The predictive dynamic model of HFS in patients receiving capecitabine allows the prediction of toxicity risk based on cumulative capecitabine dose and previous HFS grade. This dose-toxicity model will be useful in developing Bayesian individual treatment adaptations and may be of use in the clinic.

Skin Coverage of the Middle-Distal Segment of the Leg With a Pedicled Perforator Flap

Objective: This is a clinical study of our experience using pedicle perforator flaps to cover skin defects in the middle and distal segment of the leg. Design: Prospective study. Setting: University hospital. Patients/Intervention: Twenty-four patients underwent treatment of a skin defect in the middle or distal segment of the leg by means of pedicled flaps based on perforating arteries. The perforating arteries were located before the operation by means of echo-Doppler examination. The flaps were planned in propeller fashion (21 cases) and as advancement (three cases). Main Outcome Measurements: The results were evaluated according the origin of perforator flap, size of the flap, and donor area and viability of the flap. The success rate of the echo-Doppler to identify the location of perforator vessel was also evaluated. Results: In nine cases, the perforating vessels originated from the fibular artery, in 10 the posterior tibial artery, and in five the anterior tibial artery. The mean size of the flaps was 5 cm in width by 12 cm in length. The success rate using an echo-Doppler was 87%. The flaps were fully viable in 20 cases and partially viable in four cases. Conclusion: On the basis of these results, it is concluded that perforating flaps are a good choice of treatment for skin losses, especially in the distal segment of the leg, and could be an alternative option for the use of free microsurgical flaps.