A multiscale MD-FE model of diffusion in composite media with internal surface interaction based on numerical homogenization procedure

Mass transport by diffusion within composite materials may depend not only on internal microstructural geometry, but also on the chemical interactions between the transported substance and the material of the microstructure. Retrospectively, there is a gap in methods and theory to connect material microstructure properties with macroscale continuum diffusion characteristics. Here we present a new hierarchical multiscale model for diffusion within composite materials that couples material microstructural geometry and interactions between diffusing particles and the material matrix. This model, which bridges molecular dynamics (MD) and the finite element (FE) method, is employed to construct a continuum diffusion model based on a novel numerical homogenization procedure. The procedure is general and robust for evaluating constitutive material parameters of the continuum model. These parameters include the traditional bulk diffusion coefficients and, additionally, the distances from the solid surface accounting for surface interaction effects. We implemented our models to glucose diffusion through the following two geometrical/material configurations: tightly packed silica nanospheres, and a complex fibrous structure surrounding nanospheres. Then, rhodamine 6G diffusion analysis through an aga-rose gel network was performed, followed by a model validation using our experimental results. The microstructural model, numerical homogenization and continuum model offer a new platform for modeling and predicting mass diffusion through complex biological environment and within composite materials that are used in a wide range of applications, like drug delivery and nanoporous catalysts.

Lower incidence of hepatic metastases of colorectal cancer in patients with chronic liver diseases: meta-analysis

BACKGROUND/AIMS

The rarity of metastatic malignancy in injured liver has been noticed. This meta-analysis evaluates the difference in occurrence of metastatic colorectal cancer in healthy and chronically injured liver.

METHODOLOGY

Literature search of occurrence of metastatic colorectal cancer in chronically injured liver opposed to healthy liver was conducted. Chronically injured/damaged liver included cirrhosis, steatosis or fatty liver and infection with Hepatitis virus B or C.

RESULTS

A total of 7 retrospective studies between 1992 and 2010 matched the selection criteria with total of 4049 patients. Results suggest significantly lower incidence of colorectal metastasis in chronically injured liver (Pooled odds ratio = 0.260 (95% CI = 0.18 to 0.38); χ² (test odds ratio differs from 1) = 45.90 (df = 1); p <0.0001).

CONCLUSIONS

Patients with chronic liver injury have significantly lower occurrence of hepatic metastasis of primary colorectal cancer than the patients with healthy liver.

Clinical and seasonal variations of nutritional risk screening in patients scheduled for rehabilitation after heart surgery

BACKGROUND

Current knowledge on the pervasiveness of increased nutritional risk in cardiovascular diseases is limited. Our aim was to analyze the characteristics of nutritional risk screening in patients scheduled for rehabilitation after heart surgery. Prevalence and extent of nutritional risk were studied in connection with patients' characteristics and seasonal climate effects on weight loss dynamics.

METHODS

The cohort included 65 consecutive patients with an age range of 25-84 years, 2-6 months after surgical treatment for ischemic or valvular heart disease. Nutritional risk screening was appraised using a standardized NRS-2002 questionnaire. Groups were analyzed according to a timeline of rehabilitation according to the "cold" and "warm" seasons of the moderate Mediterranean climate in Opatija, Croatia.

RESULTS

Increased nutritional risk scores (NRS-2002) of >3 were found in 96% of studied patients. Mean NRS-2002 of patients was 5.0 ± 1.0, with a percentage weight loss history of 11.7% ± 2.2% (4.6-19.0). Risk was found to be more pronounced during the warmer season, with NRS-2002 scores of 5.3 ± 0.7 versus 4.8 ± 1.1 (P = 0.136) and greater loss of weight of 13.0% ± 3.2% versus 10.6% ± 3% (P = 0.005), respectively. Increased nutritional risk correlated significantly with creatinine concentrations (rho = 0.359; P = 0.034 versus 0.584; P = 0.001, respectively). Significant discordance in correlations was found between NRS-2002 and the decrease in left ventricle systolic function (rho correlation coefficient [rho-cc] = -0.428; P = 0.009), the increase in glucose concentrations (cc = 0.600; P < 0.001), and the decrease in erythrocyte counts (cc = -0.520; P = 0.001) during the colder season.

CONCLUSION

Increased nutritional risk was found to be frequently expressed in the course of rehabilitation after heart surgery. Although seasonal climate effects influenced the weight loss dynamics, the impact on reproducibility of NRS-2002 was clinically less important. Further studies on the connection of nutritional risk with composited end points might offer improvements in overall quality of treatment.

Hippocampal hypertrophy and sleep apnea: a role for the ischemic preconditioning?

The full impact of multisystem disease such as obstructive sleep apnoea (OSA) on regions of the central nervous system is debated, as the subsequent neurocognitive sequelae are unclear. Several preclinical studies suggest that its purported major culprits, intermittent hypoxia and sleep fragmentation, can differentially affect adult hippocampal neurogenesis. Although the prospective biphasic nature of chronic intermittent hypoxia in animal models of OSA has been acknowledged, so far the evidence for increased ‘compensatory’ neurogenesis in humans is uncertain. In a cross-sectional study of 32 patients with mixed severity OSA and 32 non-apnoeic matched controls inferential analysis showed bilateral enlargement of hippocampi in the OSA group. Conversely, a trend for smaller thalami in the OSA group was noted. Furthermore, aberrant connectivity between the hippocampus and the cerebellum in the OSA group was also suggested by the correlation analysis. The role for the ischemia/hypoxia preconditioning in the neuropathology of OSA is herein indicated, with possible further reaching clinical implications.

The IMPACT-III (HR) questionnaire: a valid measure of health-related quality of life in Croatian children with inflammatory bowel disease

BACKGROUND AND AIMS

To assess the reliability and validity of IMPACT-III (HR), a disease-specific, health-related quality of life instrument in Croatian children with inflammatory bowel disease.

METHODS

In a multicenter study, 104 children participated in a validation study of IMPACT-III (HR) cross-culturally adapted for Croatia. Factor analysis was used to determine optimal domain structure for this cohort, analysis of Cronbach's alpha coefficients to test internal reliability, ANOVA to assess discriminant validity, and correlation with Pediatric Quality of Life Inventory, Version 4.0 (PedsQL) using Pearson correlation coefficients to assess concurrent validity.

RESULTS

Cronbach's alpha for the IMPACT-III (HR) total score was 0.92. The most robust factor solution was a 5-domain structure: Symptoms, Concerns, Socializing, Body Image, and Worry about Stool, all of which demonstrated good internal reliability (α=0.60-0.89), but two items were dropped to achieve this. Discriminant validity was demonstrated by significant differences (P<0.001) in mean IMPACT-III (HR) scores between quiescent and mild or moderate-severe disease activity groups for total (148 vs. 139 or 125) and following factor scores: Symptoms (84 vs. 71 or 61), Socializing (91 vs. 83 or 76), and Worry about Stool (significant only between quiescent and moderate-severe groups, 90 vs. 62, respectively). Concurrent validity of IMPACT-III (HR) with PedsQL showed significant correlation, which was strongest when similar domains were compared.

CONCLUSION

IMPACT-III (HR) appears to be useful tool to measure health-related quality of life in Croatian children with Crohn's disease and ulcerative colitis.

Patients and health care professionals: partners in health care in Croatia?

OBJECTIVES

To explore quality in hospitals from the patients' and health care professionals' perspective in line with Act on the Protection of Patient Rights.

DESIGN

A qualitative study using a focus group design and semi-structured interviews.

METHODS

Three focus groups among health care professionals were conducted with 51 participants: 24 nurses and medical technicians, 15 physicians, 12 residents, followed by additional interviews (20 nurses and medical technicians, 10 physicians, and 2 residents). Twenty patients were interviewed at the time of their discharge from the hospital. Collected data were analysed using thematic analysis.

RESULTS

Patients identified waiting for medical treatments/procedures as the most concerning factor, followed by changes in administration procedures and admission in hospitals. From the physicians' and nurses' perspective, the main topics were inadequate resources to work with and inadequate working environment. Residents emphasized administration and lack of adequate equipment in contrast to other health care professionals. Both patients and health care professionals identified similar organizational and administrative issues impacting on service delivery.

CONCLUSIONS

Health care providers and patients equally recognize the factors that impact upon quality of care. This problem is beyond the health care professionals' possibility to solve, which is the main source of stress and burnout that influence the quality of care. These factors cannot be overcome, by either health care professionals or patient organizations working alone. Greater partnership between health providers and patient associations is needed.

STATEMENT OF CONTRIBUTION

What is already known on this subject? Healthcare providers and patients have the same goal: good quality of care and safety. Croatia has undergone significant socio-economic and political changes, which have affected the organization of the health care system. The patient experience is positively associated with clinical effectiveness and patient safety. What does this study add? From the perspective of patients and health professionals the main concern regarding quality of care is the organization of work in hospitals. Croatian patients and health professionals show considerable agreement with regard to the administrative problems in hospitals. Solutions that include only efforts on the part of the health care worker will fail.

Spectroscopic method for measuring refractive index

A method for routine, but precise measurements of refractive index is described. The method is fast and accurate. It is based on the analysis of interference fringes, and uses positions of the fringe maxima and/or minima and a precise measurement of sample thickness to extract refractive index. An extremely dense dataset of refractive index values over the entire spectral range of interest can be routinely obtained.

On the nature of the evanescent wave

This is an unusual paper in that it does not address a particular research topic or present a novel experimental method or a new theoretical result. This paper addresses our basic understanding of the nature of the evanescent wave, the wave that is the basis of the entire field of Attenuated Total Reflection (ATR) spectroscopy. I recently had the opportunity to reexamine the foundations of ATR spectroscopy and was surprised to have had to change my own mental picture of the evanescent wave that I have built over the last 25 years. Over the years I have had numerous discussions with a large number of workers in the field as well as with my former mentor, and one of the originators and the principal developer of ATR spectroscopy, the late N.J. Harrick. Everything brought up in all these discussions was perfectly consistent with my old mental picture of the evanescent wave. Thus, I believe that the picture of the evanescent wave that I had is virtually universally held by workers in the field. This paper describes the new picture of the evanescent wave that emerged from said reexamination process.