Long-term histologic and mechanical results of a Permacol™ abdominal wall explant

Purpose  

We hypothesize that Permacol™ may allow controlled integration over time while providing long-term mechanical stability and native tissue remodeling. The purpose of this report is to investigate these properties in an explanted piece of Permacol™ after 2 years in vivo.     

Thermophysical Properties and Molecular Relaxations in Cured Epoxy Resin + PEO Blends: Observations on Factors Controlling Miscibility

Summary: Thermophysical properties and molecular relaxations in aromatic amine‐cured diglycidyl ether of bisphenol‐A (DGEBA) epoxy oligomer and poly(ethylene oxide) (PEO) mixtures were determined by DSC and dielectric techniques (TSC, DRS). The binary blends were judged to be fully miscible in the amorphous state (w_PEO < 40 wt.‐%), as evidenced by the single composition‐dependent glass transition temperatures T_gs. In the amorphous blends, negative deviations of dielectric/thermal T_g‐estimates from the linear mixing rule or the behavior predicted by the Fox equation reveal weaker intermolecular interactions, compared to strong self‐association of hydroxyls in the cured thermoset. Morphological changes in PEO‐rich blends (w_PEO ≥ 40 wt.‐%) are in accordance with their complicated interface structure, previously reported to consist of amorphous PEO regions, branched epoxy resin chains and an imperfect epoxy resin network located between PEO lamellae. In these blends, PEO crystallites exert steric hindrances in the amorphous regions, causing strong T_g upshifts. Changes in the relaxation dynamics of glyceryl segments (e.g., in the activation energy barrier and relaxation strength) are in accordance with the idea that the close matching between the molecular polarities of PEO, epoxy resin and the cure agent significantly contributes to the observed miscibility.

Plots of transition temperatures as function of blend composition.     

Social network concordance in food choice among spouses, friends, and siblings

Objectives. We investigated whether eating behaviors were concordant among diverse sets of social ties.Methods. We analyzed the socioeconomic and demographic distribution of eating among 3418 members of the Framingham Heart Study observed from 1991 to 2001. We used a data-classification procedure to simplify choices into 7 nonoverlapping patterns that we matched with information on social network ties. We used correlation analysis to examine eating associations among 4 types of peers (spouses, friends, brothers, and sisters). Longitudinal multiple logistic regression was used to evaluate evidence for peer influences on eating.Results. Of all peer types, spouses showed the strongest concordances in eating patterns over time after adjustment for social contextual factors. Across all peers, the eating pattern most likely to be shared by socially connected individuals was “alcohol and snacks.” Models estimating one''s current eating pattern on the basis of a peer''s prior eating provided supportive evidence of a social influence process.Conclusions. Certain eating patterns appeared to be socially transmissible across different kinds of relationships. These findings represent an important step in specifying the relevant social environment in the study of health behaviors to include eating.Food consumption is incontrovertibly linked with public health outcomes ranging from obesity to cardiovascular disease and diabetes.^1,2 Research has found that eating with others affects what an individual consumes³ and, more recently, that obesity status is influenced by ties in social networks.⁴ Together, this knowledge highlights the value of understanding the roles that relationships play in our eating behaviors. To date, however, there has been little research investigating the relationship between patterns of food consumption and the complex patterns of human connectedness. To what degree is the eating behavior of one''s peers associated with what one eats?Research on commensality and health concordance gives some insight into this question. For instance, eating with others is associated with greater ingestion than when food is consumed alone⁵; friends and family members are associated with greater “social facilitation” than are other kinds of relationships, including co-workers, classmates, lovers, or roommates³; family members are more likely to eat together than friends are⁶; and cognitive dietary restraint, disinhibition, and susceptibility to hunger have a significant familial resemblance.⁷ Research on diet in the context of health concordance has found that newly coupled individuals tend to increase their consumption of fruits and vegetables, low-fat foods, and breakfasts together, while consuming less take-out food,⁸ and that spouses’ nutrient consumption is modestly correlated.⁹ Couples shape one another''s choices, although female partners tend to have more influence over male choices.¹⁰ However, a great deal of what we know of commensality has been gleaned from laboratory research rather than real-world studies of eating behavior, thereby excluding the social environment. Similarly, our knowledge of diet concordance in observational studies has largely issued from small-scale, cross-sectional designs.¹¹Previous work on social networks and health has found that weight status is related to patterns of social relations^4,12 and that drinking behaviors can spread in a social network.¹³ However, whether food consumption per se is subject to similar forms of peer influence in a network setting has not been examined. Our objective was to investigate whether connections with particular kinds of intimate relations (spouses, friends, and siblings) were predictive of eating patterns of connected individuals in a large prospective cohort study over time. To address this question, food patterns were first enumerated from food-frequency questionnaires. We then performed a series of correlation analyses to assess food pattern concordance, and we fit a series of longitudinal multiple logistic regression models to test for peer influence on eating among close social contacts.     

Dynamic social networks promote cooperation in experiments with humans

Human populations are both highly cooperative and highly organized. Human interactions are not random but rather are structured in social networks. Importantly, ties in these networks often are dynamic, changing in response to the behavior of one's social partners. This dynamic structure permits an important form of conditional action that has been explored theoretically but has received little empirical attention: People can respond to the cooperation and defection of those around them by making or breaking network links. Here, we present experimental evidence of the power of using strategic link formation and dissolution, and the network modification it entails, to stabilize cooperation in sizable groups. Our experiments explore large-scale cooperation, where subjects' cooperative actions are equally beneficial to all those with whom they interact. Consistent with previous research, we find that cooperation decays over time when social networks are shuffled randomly every round or are fixed across all rounds. We also find that, when networks are dynamic but are updated only infrequently, cooperation again fails. However, when subjects can update their network connections frequently, we see a qualitatively different outcome: Cooperation is maintained at a high level through network rewiring. Subjects preferentially break links with defectors and form new links with cooperators, creating an incentive to cooperate and leading to substantial changes in network structure. Our experiments confirm the predictions of a set of evolutionary game theoretic models and demonstrate the important role that dynamic social networks can play in supporting large-scale human cooperation.     

Correlated genotypes in friendship networks

It is well known that humans tend to associate with other humans who have similar characteristics, but it is unclear whether this tendency has consequences for the distribution of genotypes in a population. Although geneticists have shown that populations tend to stratify genetically, this process results from geographic sorting or assortative mating, and it is unknown whether genotypes may be correlated as a consequence of nonreproductive associations or other processes. Here, we study six available genotypes from the National Longitudinal Study of Adolescent Health to test for genetic similarity between friends. Maps of the friendship networks show clustering of genotypes and, after we apply strict controls for population stratification, the results show that one genotype is positively correlated (homophily) and one genotype is negatively correlated (heterophily). A replication study in an independent sample from the Framingham Heart Study verifies that DRD2 exhibits significant homophily and that CYP2A6 exhibits significant heterophily. These unique results show that homophily and heterophily obtain on a genetic (indeed, an allelic) level, which has implications for the study of population genetics and social behavior. In particular, the results suggest that association tests should include friends' genes and that theories of evolution should take into account the fact that humans might, in some sense, be metagenomic with respect to the humans around them.     

Phantom-based assessment of motion and needle targeting accuracy of robotic devices for magnetic resonance imaging-guided needle biopsy

Background

The current study proposes simple methods for assessing the performance of robotic devices intended for Magnetic Resonance Imaging (MRI)-guided needle biopsy.

Methods

In-house made agar-based breast phantoms containing biopsy targets served as the main tool in the evaluation process of an MRI compatible positioning device comprising a needle navigator. The motion accuracy of mechanical stages was assessed by calliper measurements. Laboratory evaluation of needle targeting included a repeatability phantom test and a laser-based method. The accuracy and repeatability of needle targeting was also assessed by MRI.

Results

The maximum error of linear motion for steps up to 10 mm was 0.1 mm. Needle navigation relative to the phantom and alignment with the various biopsy targets were performed successfully in both the laboratory and MRI settings. The proposed biopsy phantoms offered tissue-like signal in MRI and good haptic feedback during needle insertion.

Conclusions

The proposed methods could be valuable in the process of validating the accuracy of MRI-guided biopsy robotic devices in both laboratory and real environments.     

Pediatricians' awareness of and attitudes about four clinical practice guidelines

BACKGROUND: The increasing complexity of medical care and a desire to increase quality and control costs have led to growing use of clinical practice guidelines (CPGs). It is unclear how helpful these guidelines are to the practitioners expected to use them. We surveyed pediatricians about their knowledge and impressions of four well-publicized CPGs: the American Academy of Pediatrics' "Practice Parameter for Hyperbilirubinemia in Newborns" (hyperbilirubinemia), "A Guideline for the Management of Febrile Infants" (fever), the Agency for Health Care Policy and Research's "Guideline for Otitis Media With Effusion" (otitis), and the US Preventive Services Task Force Guide to Clinical Preventive Services (preventive care). OBJECTIVES: 1) What percentage of practicing pediatricians are aware of these guidelines? 2) How helpful do they find them? 3) What are practitioners' perceived limitations of these guidelines? 4) Have these guidelines affected provider behavior? 5) Are there features of a provider's training or practice that are associated with changing practice as a result of guidelines? DESIGN: A national survey of 600 pediatricians selected at random from the American Medical Association master file. RESULTS: A total of 300 of 555 eligible participants (54%) returned surveys. Of the respondents, 66% were aware of the hyperbilirubinemia guideline, 64% of the fever guideline, 50% of the otitis guideline, but only 16% knew of the preventive care guidelines. Mean helpfulness scores (1 to 10 scale, where 1 = "not at all helpful" and 10 = "extremely helpful") ranged from 3.67 to 6.67 for the different guidelines. In terms of limitations, 15% to 33% of respondents reported that CPGs were "too cookbook," 6% to 19% reported that they were "too time-consuming," and 4% to 16% reported that they were "too cumbersome." Additional reported limitations were believing that a guideline left no room for personal experience and judgment, concern of increased liability risk, and poor parental acceptance of CPG recommendations. The proportions reporting change in management as a result of a CPG were 28% for the hyperbilirubinemia guideline, 36% for the fever guideline, 19% for the preventive care guidelines, and 28% for the otitis guideline. Mean helpfulness scores reported by nonuniversity-affiliated physicians were significantly higher than those reported by university-affiliated physicians. In a regression model of respondents aware of a particular guideline, more recent graduation from medical school and increased helpfulness scores were associated with guideline-related behavior change. CONCLUSION: In their present form, CPGs are not perceived as very helpful by most practitioners. More recent medical school graduates and nonuniversity-affiliated physicians are more likely to find them helpful and more likely to change their behavior because of them.