Is there a Relationship between the Elongational Viscosity and the First Normal Stress Difference in Polymer Solutions?

We investigate a variety of different polymer solutions in shear and elongational flow. The shear flow is created in the cone-plate-geometry of a commercial rheometer. We use capillary thinning of a filament that is formed by a polymer solution in the Capillary Breakup Extensional Rheometer (CaBER) as an elongational flow. We compare the relaxation time and the elongational viscosity measured in the CaBER with the first normal stress difference and the relaxation time that we measured in our rheometer. All of these four quantities depend on different fluid parameters - the viscosity of the polymer solution, the polymer concentration within the solution, and the molecular weight of the polymers - and on the shear rate (in the shear flow measurements). Nevertheless, we find that the first normal stress coefficient depends quadratically on the CaBER relaxation time. A simple model is presented that explains this relation

Converting Capital: The Experiences of Latinas/os in Graduate Health Care Programs

This qualitative study combines critical race theory, cultural capital theory, and counter-storytelling to examine the experiences of Latina/o in graduate health care programs. Community cultural wealth provided the framework to investigate the mechanisms by which students converted their sociocultural assets into the kinds of social, cultural, and educational capital needed to succeed in a graduate program and pursue their career goals. A qualitative content analysis was employed to interpret participants’ conversion experiences. The forms of community cultural wealth described by Yosso – aspirational, linguistic, familial, navigational, social, and resistant – intersected and interacted with one another. Aspirational and linguistic forms of capital were converted into occupational attainment; familial capital was converted into educational and occupational outcomes; navigational and social forms of capital were converted into educational outcomes, and resistant capital was converted into civic engagement. Recommendations for practice and future research are discussed

“Come and See for Yourself”: Exploration of Mindfulness Practice by First-Year College Students

This grounded theory study aims at explaining how college freshmen develop and stay engaged with a regular mindfulness practice, and the benefits they experience. The authors investigated an intentional effort to integrate mindfulness practices in the curriculum of a First-Year Seminar and English Composition course. The results presented here support existing findings concerning the integration of mindfulness practice in higher education settings. This study also advances unique findings relative to utilizing classroom settings to introduce first-year students to the practice, as a long as the course follows a regular structure (i.e., attendance, homework assignments). The substantive theory presented describes how students developed a practice routine and made the practice relevant for their academic and personal lives. Recommendations for practice and future research are included

Origin and fate of branched tetraether lipids in river drainage systems : Implications for the use of the MBT/CBT proxy as a continental palaeothermometer in marine sedimentary records

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane lipids ofbacteria. The number of methyl groups of the alkyl chains in brGDGTs correlates with the mean annual air temperature (MAAT) and soil pH, while the number of cyclopentane moieties correlates with soil pH. Based on this observation the methylation index of branched tetraethers (MBT) and the cyclisation index of branched tetraethers (CBT) were introduced. Since brGDGTs are found in large quantities in soil, it was assumed that they are washed into rivers by erosion and transported to the ocean. Hence, the MBT/CBT proxy can be used in river influenced marine settings to reconstruct past MAAT and soil pH of the river basin. In this study the applicability of the MBT/CBT proxy in diverse river systems was assessed, by detailed studies of two river systems that are different in terms of river size and climate setting (Amazon River and Tagus River). BrGDGTs in drainage basin, soils and river suspended particulate matter (SPM) were compared to those in marine SPM and surface sediments. Core lipid (CL) and intact polar lipid (IPL)-derived brGDGTs were analyzed, in order to distinguish recently produced (IPL-derived) GDGTs from older (CL) GDGTs. The majority of brGDGTs in the Amazon River is derived from lowland basin soils. However, the distribution of CL and IPL-derived brGDGTs was slightly different to that of the soils, which showed that in-situ production of brGDGTs also played a role. The influence of seasonal variation on the brGDGT distribution is relatively small, but significant differences were detected. During the high water season the input of brGDGTs from soil increased, which was seen in increased brGDGT concentrations and a brGDGT distribution that was most similar to that of soil. During the other seasons the influence of in-situ production of brGDGTs increased. In the Amazon shelf and fan, the delivery of brGDGTs from the Amazon River was evident. However, further away from the river, the distributions of CL brGDGTs in marine SPM and sediments varied widely, since this difference was also found in IPL-derived brGDGTs it is most likely due to marine in-situ production. In the Tagus basin soils the brGDGT distributions were very variable and did not reflect the local MAAT and soil pH. The concentrations of brGDGTs in river SPM were substantially higher and the distributions were different compared to those of the drainage basin soils. This indicates that brGDGTs are mainly produced in the river itself. Therefore, the MAAT and soil pH cannot be reconstructed with the commonly used soil calibrations. Along the Portuguese margin the brGDGT concentrations rapidly decreased with increasing distance from the shore. The brGDGT distributions in marine SPM and surface sediments also changed, indicating that marine in-situ production takes place. In conclusion, this study emphasizes the importance of a detailed study of a river basin to interpret the MBT/CBT records for paleoreconstructions in adjacent marine setting. In general, it is recommendable to apply the MBT/CBT proxy only to sediment which was under strong river influence

Unconditional entanglement interface for quantum networks

Entanglement drives nearly all proposed quantum information technologies. The suppression of the uncertainty in joint quadrature measurements below the level of vacuum fluctuations is a signature of non-classical correlations. Entangling frequency modes of optical fields has attracted increased attention in recent years, as a quantum network would rely on interfacing light at telecommunication wavelengths with matter-based quantum memories that are addressable at visible wavelengths. By up-converting part of a 1550 nm squeezed vacuum state to 532 nm, we demonstrate the generation and complete characterization of strong continuous-variable entanglement between widely separated frequencies. Non-classical correlations were observed in joint quadrature measurements of the 1550 nm and 532 nm fields, showing a maximum noise suppression 5.5 dB below vacuum. A spectrum was measured to demonstrate over 3 dB noise suppression up to 20 MHzmeasurement frequency. Our versatile technique combines strong non-classical correlations, large bandwidth and, in principle, the ability to entangle the telecommunication wavelength of 1550 nm with any optical wavelength, making this approach highly relevant to emerging proposals for quantum communication and computing

Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT’/CBT paleothermometer

Branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are transported from soil to marine sediment by rivers, have been used to reconstruct the mean annual air temperature (MAAT) and soil pH of the drainage basin using the methylation index of branched tetraethers (MBT, recently refined as MBT') and cyclization index of branched tetraethers (CBT) from coastal marine sediment records. In this study we are tracing the brGDGTs from source to sink in the Tagus River basin, the longest river system on the Iberian Peninsula, by determining their concentration and distribution in soils, river suspended particulate matter (SPM), riverbank sediments, marine SPM, and marine surface sediments. The concentrations of brGDGTs in river SPM were substantially higher and their distributions were different compared to those of the drainage basin soils. This indicates that brGDGTs are mainly produced in the river itself. In the marine environment, the brGDGT concentrations rapidly decreased with increasing distance from the Tagus estuary. At the same time, the brGDGT distributions in marine sediments also changed, indicating that marine in-situ production also takes place. These results show that there are various problems that complicate the use of the MBT'/CBT for paleoreconstructions using coastal marine sediments in the vicinity of a river. However, if the majority of brGDGTs are produced in the river, it might be possible to reconstruct the environmental (temperature and pH) conditions of the river water using appropriate aquatic calibrations, provided that marine core locations are chosen in such a way that the brGDGTs in their sediments are predominantly derived from riverine in-situ production