Topology, braids and mixing in fluids

Stirring of fluid with moving rods is necessary in many practical applications to achieve homogeneity. These rods are topological obstacles that force stretching of fluid elements. The resulting stretching and folding is commonly observed as filaments and striations, and is a precursor to mixing. In a space-time diagram, the trajectories of the rods form a braid, and the properties of this braid impose a minimal complexity in the flow. We review the topological viewpoint of fluid mixing, and discuss how braids can be used to diagnose mixing and construct efficient mixing devices. We introduce a new, realizable design for a mixing device, the silver mixer, based on these principles.     

Ending on a high note: Adding a better end to effortful study.

Remembered utility is the retrospective evaluation about the pleasure and pain associated with a past experience. It has been shown to influence prospective choices about whether to repeat or to avoid similar situations in the future (D. Kahneman 2000; D. Kahneman, D. L. Fredrickson, C. A. Schreiber, & D. A. Redelmeier, 1993). Evaluations about our hedonic past often disregard the duration of the experience and are influenced more by the peak and the final levels of discomfort (B. L. Fredrickson & D. Kahneman, 1993). Two experiments explored the remembered discomfort of an effortful learning experience and the influence of this evaluation on prospective study choices. The design of the studies mimicked D. Kahneman et al.'s (1993) cold-pressor study, but used an exceptionally challenging learning experience in place of the painful experience of submerging one's hand in ice water. An extremely effortful study episode extended by a more moderate interval was preferred to a shorter, unextended interval, despite better test performance following the shorter interval. Future study choices reflected this preference. These findings suggest that the act of acquiring knowledge has value in the learning process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compensation of flow maldistribution in fin-and-tube evaporators for residential air-conditioning

Compensation of flow maldistribution in multi-channel fin-and-tube evaporators for residential air-conditioning is investigated by numerical modeling. The considered sources of maldistribution are distribution of the liquid and vapor phases in the distributor and non-uniform airflow distribution. Fin-and-tube heat exchangers usually have a predefined circuitry, however, the evaporator model is simplified to have straight tubes, in order to perform a generic investigation. The compensation of flow maldistribution is performed by control of the superheat in the individual channels. Furthermore, the effect of combinations of individual maldistribution sources is investigated for different evaporator sizes and outdoor temperatures. It is shown that a decrease in cooling capacity and coefficient of performance by flow maldistribution can be compensated by the control of individual channel superheat. Alternatively, a larger evaporator may be used.     

High sensitivity and analyte capture with desorption/ionization mass spectrometry on silylated porous silicon

Silylation chemistry on porous silicon provides for ultrahigh sensitivity and analyte specificity with desorption/ionization on silicon mass spectrometry (DIOS-MS) analysis. Here, we report that the silylation of oxidized porous silicon offers a DIOS platform that is resistant to air oxidation and acid/base hydrolysis. Furthermore, surface modification with appropriate hydrophobic silanes allows analytes to absorb to the surface via hydrophobic interactions for direct analyte extraction from complex matrixes containing salts and other nonvolatile interferences present in the sample matrix. This enables rapid cleanup by simply spotting the sample onto the modified DIOS target and removing the liquid phase containing the interferences. This approach is demonstrated in the analysis of protein digests and metabolites in biofluids, as well as for the characterizing of inhibitors from their enzyme complex. An unprecedented detection limit of 480 molecules (800 ymol) for des-Arg(9)-bradykinin is reported on a pentafluorophenyl-functionalized DIOS chip.     

Occupational Factors and 5-Year Weight Change Among Men in a Danish National Cohort.

This study explored whether factors related to the work environment could predict changes in body mass index (BMI) and whether the effect of psychosocial factors was dependent on baseline BMI. The sample consisted of 1,980 male employees from the Danish National Work Environment Cohort Study. Changes in BMI between 1995 and 2000 were analyzed, by multiple regression, as a function of background variables and a series of occupational variables obtained in 1995. Age, baseline BMI, job insecurity, and psychological demands predicted changes in BMI. Job insecurity and high or low psychological demands increased the likelihood of weight gain among obese employees, whereas they increased the likelihood of weight loss among employees with a low BMI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ongoing efforts to improve the international nuclear and radiological emergency response

It is recognised that states, through the development of a consistent, coherent and sustainable joint programme for improved and more efficient international responses to nuclear and radiological emergencies, could achieve a better and more cost-effective response capability. Enhanced efforts by IAEA member states and the IAEA secretariat to improve the implementation of the Convention on Early Notification of a Nuclear Accident and the Convention on Assistance in Case of a Nuclear Accident or Radiological Emergency have been initiated, establishing a national competent authority coordination group (NCACG) and a long-term action plan for the work.     

Quantitative imaging of bromine-76 and yttrium-86 with PET: a method for the removal of spurious activity introduced by cascade gamma rays

Positron Emission Tomography of bromine-76 and yttrium-86 results in the detection of coincident events that are not strictly associated with annihilation photon pairs. Instead, these coincidences occur because prompt gamma rays emitted by these nuclides result in cascades of photons that are emitted within the timing window of the PET scanner. Pairs of detected photons from these cascades are not angularly correlated and therefore contain little information regarding the location of their source. Furthermore, these coincidences are not removed by correction procedures (e.g., randoms, scatter) routinely applied to PET data. If left uncorrected, the cascade coincidences will result in spurious apparent activity within the PET images. A correction, applied within projection space, that removes the cascade coincidence signal from septa-in (i.e., two-dimensional) datasets is proposed and tested on phantom data.     

Inability to predict cardiovascular disease from hostility scores or MMPI items related to Type A behavior.

[Correction Notice: An erratum for this article was reported in Vol 58(5) of Journal of Consulting and Clinical Psychology (see record 2008-10621-001). In the article, the mean Ho scores are incorrect and some reported information is no longer relevant. The entries have been corrected and are included in the erratum. All other analyses and all conclusions are correct as reported.] Medical and psychological data collected for 30 years on a group of 280 men (mean age in 1947&=&45 years) were evaluated to identify the personality characteristics and attitudes that might be predictive of the later development of coronary heart disease (CHD). Minnesota Multiphasic Personality Inventory (MMPI) Hostility scores did not predict CHD in this population. A 35-item scale derived from MMPI items judged to reflect the Type A construct and from other personality scales did not predict the later incidence of myocardial infarctions or other evidence of CHD. It is therefore possible that personality factors may not be strong predictors of CHD in particular samples. (PsycINFO Database Record (c) 2010 APA, all rights reserved)