Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers

A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 microm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures.

Influence of dye molecules on the birefringence of liquid crystal mixtures at near infrared frequencies

The optical properties of nematic liquid crystals have been extensively exploited in the production of devices working in the visible range of the spectrum. These same properties can be employed to make devices that function in the near infrared as required for telecommunications applications. However, it is generally observed that the birefringence of liquid crystal mixtures decreases with increasing wavelength, making it important to identify new materials, optimized for use in the near infrared region. One route to high birefringence is to operate close to an absorption band edge, which in the present context implies choosing highly conjugated materials which are potentially colored and, thus, not suited to traditional display applications. In this paper we explore the usefulness of dye molecules as birefringence enhancers in mixtures with conventional nematic liquid crystals. The optical properties, in particular, the absorption edge, polarizability, and birefringence, of families of known dyes are calculated at optical (589 nm) and infrared (1550 nm) wavelengths, using electronic density functional theory. We demonstrate the expected correlation between the proximity of the absorption edge and the magnitude of the birefringence, and estimate the birefringence enhancement occurring when each dye is incorporated in a guest-host system.

Measuring children's participation in recreation and leisure activities: construct validation of the CAPE and PAC

There is a need for psychometrically sound measures of children's participation in recreation and leisure activities, for both clinical and research purposes. This paper provides information about the construct validity of the Children's Assessment of Participation and Enjoyment (CAPE) and its companion measure, Preferences for Activities of Children (PAC). These measures are appropriate for children and youth with and without disabilities between the ages of 6 and 21 years. They provide information about six dimensions of participation (i.e. diversity, intensity, where, with whom, enjoyment and preference) and two categories of recreation and leisure activities: (i) formal and informal activities; and (ii) five types of activities (recreational, active physical, social, skill-based and self-improvement). This paper presents information about the performance of the CAPE and PAC activity type scores using data from a study involving 427 children with physical disabilities between the ages of 6 and 15 years. Intensity, enjoyment and preference scores were significantly correlated with environmental, family and child variables, in expected ways. Predictions also were supported with respect to differences in mean scores for boys vs. girls, and children in various age groups. The information substantiates the construct validity of the measures. The clinical and research utility of the measures are discussed.

Guidelines for the diagnosis and management of carcinoid tumours. Part 1: the gastrointestinal tract. A statement from a Canadian National Carcinoid Expert Group

Carcinoid tumours are relatively rare and, in general, slow growing. They can be "non-functioning" tumours, presenting as a tumour mass, or "functioning" tumours secondary to the production of several biopeptides leading to the carcinoid syndrome. Though these tumours represent 0.25% of an oncology practice, a proper understanding of the clinical course of the disease and of the importance of appropriate diagnostic and therapeutic measures is very important. Proper patient management can lead to cure, particularly if the tumour can be fully resected, or to long-term palliation with medical treatment or cytoreductive surgery, or both, with significant prolongation of survival. A good understanding of the use of somatostatin analogues to achieve effective symptomatic control and of the importance of adequate follow-up and cardiac monitoring to prevent or effectively treat cardiac complications can contribute significantly to optimal control of this complex disease, ultimately improving the quality of life of affected patients. This article, developed by a group of Canadian experts, provides a framework that will assist clinicians in taking an optimal approach to managing their patients with carcinoid tumour.

Calculation of the birefringences of nematic liquid crystals at optical and infrared wavelengths

In this paper we critically examine computational methods for predicting the birefringences of nematic liquid crystals, with a view to screening molecules for potential use in infrared applications. Using the liquid-crystal 5CB as a test molecule, we calculate molecular electronic polarizabilities using ab initio quantum-mechanical techniques and a wide range of basis sets. We show that the polarizabilities tend to a limiting value as the quality of the basis set is improved. However, the biggest hurdle remains the determination of the refractive index from the polarizability data. We examine several methods for performing this conversion and conclude that the simplest equation, due to Vuks, is adequate for predicting the birefringence, given the uncertainties involved in other parameters. The agreement between calculation and experiment is best described as "semiquantitative." We perform similar calculations for a wide range of nematic liquid crystals at both 589 and 1550 nm, taking into account the likely impact of molecular vibrations at the longer wavelength. We demonstrate that there is a simple scale factor, for conventional nematics, between the birefringence at visible wavelengths and in the infrared. Thus knowledge of the birefringence at optical wavelengths, as widely available in the literature, is a good guide to the usefulness of conventional nematic liquid crystals as active elements for optical switching in the telecommunications industry.

Neither baseline tests of molecular hypercoagulability nor D-dimer levels predict deep venous thrombosis in critically ill medical-surgical patients

OBJECTIVE

Predicting patients who are harboring asymptomatic deep venous thrombosis (DVT), or who are at particular risk of developing DVT, is a desirable clinical goal since prevention or early treatment of DVT might reduce the risk of fatal pulmonary embolism. Thus validation of simple laboratory tests that reliably predict venous thromboembolism (VTE) would be clinically very important. Tests that might be useful for these applications include markers of hypercoagulability (predicting patients at risk of DVT) and D-dimer (predicting which patients may have acute DVT).

METHODS

In a prospective cohort study we measured a panel of hypercoagulability markers at the time of ICU admission, and six commercial D-dimer assays were performed serially during the ICU stay in medical-surgical ICU patients who were screened for DVT with biweekly lower limb compression ultrasonography. Ultrasonography was also performed at the time of any clinically suspected DVT events. We matched cases with DVT with controls without DVT for length of stay in the ICU to generate receiver operating characteristics (ROC) curves.

RESULTS

One hundred ninety-seven patients were enrolled. Blood was collected on a total of 763 occasions (median number of occasions per patient: 3, range 1-21). None of the assays predicted DVT, as indicated by the areas under the ROC curves, that did not differ significantly from 50%.

CONCLUSION

In critically ill patients, neither tests of hypercoagulability nor D-dimer levels predict patients at risk of DVT and thus they should not be used to guide diagnostic testing for DVT.

Evaluating children's rehabilitation services: an application of a programme logic model

OBJECTIVES

To apply a programme logic model to evaluate the effectiveness of a new therapy service for children with special needs who were in transition from pre-school to kindergarten.

SETTING

A children's outpatient rehabilitation centre in Ontario, Canada.

MAIN OUTCOMES

The short-term outcomes included parents' perceptions of the transition process itself and the information they required, the children's skill development for the transition to kindergarten, and parents' perceptions of services and satisfaction with resources.

METHODS

A combination of quantitative methods [Goal Attainment Scaling (GAS), Measure of Processes of Care (MPOC), Client Satisfaction Questionnaire (CSQ)] and qualitative interviews were used to evaluate both the process ('Outputs') and outcomes ('Short-term objectives') of the new therapy service.

RESULTS

The children involved in the evaluation met or exceeded goals that were set by therapists and parents. Parents' perceptions of, and satisfaction with, the new service were higher than the provincial average. Qualitative data from interviews with parents and service providers supported the findings from standardized measures, and provided suggestions for future service delivery.

CONCLUSIONS

The programme logic model provided researchers and service providers a collaborative and systematic approach to conducting programme evaluation in a relatively short-time frame. It appears to be a useful option for evaluation of other children's services.

Factors affecting family-centred service delivery for children with disabilities

BACKGROUND

The provision of family-centred services (FCS) emphasizes a partnership between parents and service providers so that families are involved in every aspect of services for their child. There is evidence that providing FCS is associated with improvements in parents' satisfaction with services, decreased parental stress, and positive child outcomes.

METHODS

The purpose of this study was to examine factors that are most important in determining parent perceptions of the family centredness of care and parent satisfaction with service. A cross-sectional survey was completed by 494 parents, 324 service providers, and 15 CEOs from 16 organizations delivering children's rehabilitation services. Analyses were completed using a structural equation modelling approach.

RESULTS

Survey return rates ranged from 77 to 94%. Findings indicate that the principal determinants of parent satisfaction with services are the family-centred culture at the organization and parent perceptions of FCS. Parent satisfaction with services was also influenced by the number of places where services were received and the number of health and development problems experienced by their child.

CONCLUSION

Parent satisfaction with services is strongly influenced by the perception that services are more family centred, fewer places where services were received and fewer health and development problems for their child. Ways in which organizations can improve satisfaction through carrying out family-centred behaviours are discussed.

Hypoalbuminaemia in critically ill children: incidence, prognosis, and influence on the anion gap

AIMS

Hypoalbuminaemia has significance in adult critical illness as an independent predictor of mortality. In addition, the anion gap is predominantly due to the negative charge of albumin, thus hypoalbuminaemia may lead to its underestimation. We examine this phenomenon in critically ill children, documenting the incidence, early evolution, and prognosis of hypoalbuminaemia (<33 g/l), and quantify its influence on the anion gap.

METHODS

Prospective descriptive study of 134 critically ill children in the paediatric intensive care unit (ICU). Paired arterial blood samples were taken at ICU admission and 24 hours later, from which blood gases, electrolytes, and albumin were measured. The anion gap (including potassium) was calculated and then corrected for albumin using Figge's formula.

RESULTS

The incidence of admission hypoalbuminaemia was 57%, increasing to 76% at 24 hours. Neither admission hypoalbuminaemia, nor extreme hypoalbuminaemia (<20 g/l) predicted mortality; however, there was an association with increased median ICU stay (4.9 v 3.6 days). After correction for albumin the incidence of a raised anion gap (>18 mEq/l) increased from 28% to 44% in all samples (n = 263); this discrepancy was more pronounced in the 103 samples with metabolic acidosis (38% v 73%). Correction produced an average increase in the anion gap of 2.7 mEq/l (mean bias), with limits of agreement of +/-3.7 mEq/l.

CONCLUSION

Admission hypoalbuminaemia is common in critical illness, but is not an independent predictor of mortality. However, failure to correct the anion gap for albumin may underestimate the true anion gap, producing error in the interpretation of acid-base abnormalities. This may have treatment implications.

Incidence of hyponatraemia and hyponatraemic seizures in severe respiratory syncytial virus bronchiolitis

AIM

To document the incidence and early evolution of hyponatraemia (serum sodium < 136 mmol l(-1)) associated with respiratory syncytial virus (RSV) bronchiolitis in infants requiring intensive care.

METHODS

In a retrospective review over two winter seasons, 130 infants were admitted with confirmed RSV infection, of whom 39 were excluded because of either pre-existing risk factors for hyponatraemia: diuretic therapy (n = 14), cardiac disease (n = 10), renal disease (n = 2) or lack of admission sodium data (n = 13).

RESULTS

The incidence of admission hyponatraemia in the remaining infants (median age 6 wk) was 33% (30/91), with 11% (10/91) exhibiting a serum sodium less than 130 mmol l(-1) . Hyponatraemic and normonatraemic infants were of a similar age (median 6 vs 7 wk, p = 0.82). With fluid restriction and diuretic therapy, the incidence of hyponatraemia at 48 h had decreased to 3.3%, odds ratio 0.07 (95% confidence interval 0.02-0.24, p < 0.001). Four infants (4%) suffered hyponatraemic seizures at admission (sodium 114-123 mmol l(-1)); three had received hypotonic intravenous fluids at 100-150 ml kg(-1) d(-1) before referral to intensive care. All four were managed successfully with hypertonic (3%) saline, followed by fluid restriction, resulting in immediate termination of seizure activity and normalization of serum sodium values over 48 h.

CONCLUSION

Hyponatraemia is common among infants with RSV bronchiolitis presenting to intensive care. Neurological complications may occur and fluid therapy in vulnerable infants should be tailored to reduce this risk.

A comparison of three scoring systems for mortality risk among retrieved intensive care patients

AIMS

To assess the impact of two paediatric intensive care unit retrieval teams on the performance of three mortality risk scoring systems: pre-ICU PRISM, PIM, and PRISM II.

METHODS

A total of 928 critically ill children retrieved for intensive care from district general hospitals in the south east of England (crude mortality 7.8%) were studied.

RESULTS

Risk stratification was similar between the two retrieval teams for scores utilising data primarily prior to ICU admission (pre-ICU PRISM, PIM), despite differences in case mix. The fewer variables required for calculation of PIM resulted in complete data collection in 88% of patients, compared to pre-ICU PRISM (24%) and PRISM II (60%). Overall, all scoring systems discriminated well between survival and non-survival (area under receiver operating characteristic curve 0.83-0.87), with no differences between the two hospitals. There was a tendency towards better discrimination in all scores for children compared to infants and neonates, and a poor discrimination for respiratory disease using pre-ICU PRISM and PRISM II but not PIM. All showed suboptimal calibration, primarily as a consequence of mortality over prediction among the medium (10-30%) mortality risk bands.

CONCLUSIONS

PIM appears to offer advantages over the other two scores in terms of being less affected by the retrieval process and easier to collect. Recalibration of all scoring systems is needed.

Anti-inflammatory properties of molecular hydrogen: investigation on parasite-induced liver inflammation

Molecular hydrogen reacts with the hydroxyl radical, a highly cytotoxic species produced in inflamed tissues. It has been suggested therefore to use gaseous hydrogen in a new anti-inflammatory strategy. We tested this idea, with the aid of the equipment and skills of COMEX SA in Marseille, a group who experiments with oxygen-hydrogen breathing mixtures for professional deep-sea diving. The model used was schistosomiasis-associated chronic liver inflammation. Infected animals stayed 2 weeks in an hyperbaric chamber in a normal atmosphere supplemented with 0.7 MPa hydrogen. The treatment had significant protective effects towards liver injury, namely decreased fibrosis, improvement of hemodynamics, increased NOSII activity, increased antioxidant enzyme activity, decreased lipid peroxide levels and decreased circulating TNF-alpha levels. Under the same conditions, helium exerted also some protective effects, indicating that hydroxyl radical scavenging is not the only protective mechanism. These findings indicate that the proposed anti-inflammatory strategy deserves further attention.