Hematocrit and flow rate regulate the adhesion of platelets to von Willebrand factor

Primary hemostasis and blood clotting is known to be influenced by the red blood cell volume fraction (hematocrit) in blood. Depressed or elevated levels of red blood cells can lead to vascular perfusion problems ranging from bleeding to thrombus formation. The early stage of hemostasis and thus blood clotting in all vessel sections from the arterial to the venous system involves the adhesion of platelets to von Willebrand factor. Here we present experimental and theoretical results showing that the adhesion probability of platelets to von Willebrand factor is strongly and nonlinearly dependent on hematocrit and flow rate. Interestingly, the actual binding forces are not markedly different, which suggest that the origin of such behavior is in the distribution of platelets. Using hydrodynamic simulations of a simple model, we explicitly show that the higher the hematocrit and the flow rate, the larger the amount of platelets residing close to the wall. Our simulation results, which are in excellent agreement with the experimental observations, explain why such phenomena occur. We believe that the nonhomogeneous red blood cell distribution as well as the shear dependent hydrodynamic interaction is key for the accumulation of platelets on the vessel wall. The work we present here is an important step forward from our earlier work on single molecules and extends into the collective cellular behavior of whole blood. It sheds new light on the correlation between hematocrit and the initial steps in hemostasis and thrombosis, and outlines advances for the treatment of vascular diseases associated with high levels of red blood cells. These results are not only highly relevant for the field of hemostasis and the physics of blood clotting but are also of powerful impact in applied science most obviously in drug delivery and colloidal science.     

Bottom line: Education is the great equalizer. Or is it?

Brenda Marina and Nickole Holmes explore obstacles to access to higher education that mar our American myth.     

Mapping MSW Research Training

The surge of interest in evidence-based interventions necessitates MSW graduates who will pursue research activities in the workplace. However, evidence suggests that social workers tend not to use their research skills after graduation. This study examined three constructs that inform students’ relationships to research: (a) confidence in research skills, (b) academic activities that stimulate students’ interest in research, and (c) anticipated outcomes from future involvement in research activities. The findings suggest that MSW programs need to extend research training beyond the classroom by providing holistic research learning environments that clarify the role and purpose of research for the social work profession and provide opportunities for students to transform didactic research training into practical research skills.     

The Internalization of Jewish Values by Children Attending Orthodox Jewish Schools,and its Relationship to Autonomy-Supportive Parenting and Adjustment

The present study examined the way in which children attending Orthodox Jewish schools internalize the value of both their Jewish studies and secular studies, as well as the value of Jewish cultural practices. A distinction was made between identified internalization, where children perceive Jewish studies and Jewish culture to be an important part of their sense of self, and introjected internalization, where children participate in Jewish studies and Jewish culture because they feel like they “ought to” or because of external pressures. Primary identified reasons for their Jewish studies and Jewish cultural practices were significantly associated with positive self and teacher ratings of adjustment; internalization of secular studies was unrelated to adjustment. The study also found that parental support of autonomy, which involves allowing children some latitude in making decisions for themselves regarding religious issues, was associated with greater identification. Together, these results highlight the importance of autonomy-supportive parenting in promoting identification of adolescents' Jewish identity.     

Books received

In this study, children were shown one of three violent TV clips. Each clip showed an identical act of aggression but the perpetrator's motivation and punishment for the violent act were manipulated. Children also filled out a questionnaire that asked about their family communication patterns (FCP). Overall, children who rated higher on the communication dimension were more likely to see motivated violence as more justified, whereas children who rated higher on the control dimension were likely to see punished violence as less justified. In addition, children who were more control‐oriented and who had perceived the violent clip as justified chose aggressive story endings significantly more frequently than other children.     

The effects of R&D tax credits on patenting and innovations

Norwegian business spending on R&D is low by OECD standards. To stimulate business R&D, in 2002 the Norwegian government introduced a tax-based incentive, SkatteFUNN. We analyze the effects of SkatteFUNN on the likelihood of innovating and patenting. Using a rich database for Norwegian firms, we find that projects receiving tax credits result in the development of new production processes and to some extent the development of new products for the firm. Firms that collaborate with other firms are more likely to be successful in their innovation activities. However, the scheme does not appear to contribute to innovations in the form of new products for the market or patenting.     

Realizing Relevance: The Influence of Domain‐Specific Information on Generation of New Knowledge Through Integration in 4‐ to 8‐Year‐Old Children

In accumulating knowledge, direct modes of learning are complemented by productive processes, including self‐generation based on integration of separate episodes. Effects of the number of potentially relevant episodes on integration were examined in 4‐ to 8‐year‐olds (N = 121; racially/ethnically heterogeneous sample, English speakers, from large metropolitan area). Information was presented along with unrelated or related episodes; the latter challenged children to identify the relevant subset of episodes for integration. In Experiment 1, 4‐ and 6‐year‐olds integrated in the unrelated context. Six‐year‐olds also succeeded in the related context in forced‐choice testing. In Experiment 2, 8‐year‐olds succeeded in open‐ended and forced‐choice testing. Results illustrate a developmental progression in productive extension of knowledge due in part to age‐related increases in identification of relevant information.