Bandpass sorting of heterogeneous cells using a single surface acoustic wave transducer pair

Separation and sorting of biological entities (viruses, bacteria, and cells) is a critical step in any microfluidic lab-on-a-chip device. Acoustofluidics platforms have demonstrated their ability to use physical characteristics of cells to perform label-free separation. Bandpass-type sorting methods of medium-sized entities from a mixture have been presented using acoustic techniques; however, they require multiple transducers, lack support for various target populations, can be sensitive to flow variations, or have not been verified for continuous flow sorting of biological cells. To our knowledge, this paper presents the first acoustic bandpass method that overcomes all these limitations and presents an inherently reconfigurable technique with a single transducer pair for stable continuous flow sorting of blood cells. The sorting method is first demonstrated for polystyrene particles of sizes 6, 10, and 14.5 μm in diameter with measured purity and efficiency coefficients above 75 ± 6% and 85 ± 9%, respectively. The sorting strategy was further validated in the separation of red blood cells from white blood cells and 1 μm polystyrene particles with 78 ± 8% efficiency and 74 ± 6% purity, respectively, at a flow rate of at least 1 μl/min, enabling to process finger prick blood samples within minutes.     

Surface superconductivity in the type II Weyl semimetal TaIrTe4

The search for unconventional superconductivity in Weyl semimetal materials is currently an exciting pursuit, since such superconducting phases could potentially be topologically non-trivial and host exotic Majorana modes. The layered material TaIrTe₄ is a newly predicted time-reversal invariant type II Weyl semimetal with the minimum number of Weyl points. Here, we report the discovery of surface superconductivity in Weyl semimetal TaIrTe₄. Our scanning tunneling microscopy/spectroscopy (STM/STS) visualizes Fermi arc surface states of TaIrTe₄ that are consistent with the previous angle-resolved photoemission spectroscopy results. By a systematic study based on STS at ultralow temperature, we observe uniform superconducting gaps on the sample surface. The superconductivity is further confirmed by electrical transport measurements at ultralow temperature, with an onset transition temperature (T_c) up to 1.54 K being observed. The normalized upper critical field h*(T/T_c) behavior and the stability of the superconductivity against the ferromagnet indicate that the discovered superconductivity is unconventional with the p-wave pairing. The systematic STS, and thickness- and angular-dependent transport measurements reveal that the detected superconductivity is quasi-1D and occurs in the surface states. The discovery of the surface superconductivity in TaIrTe₄ provides a new novel platform to explore topological superconductivity and Majorana modes.     

Convergent genomic signatures of high-altitude adaptation among domestic mammals

Abundant and diverse domestic mammals living on the Tibetan Plateau provide useful materials for investigating adaptive evolution and genetic convergence. Here, we used 327 genomes from horses, sheep, goats, cattle, pigs and dogs living at both high and low altitudes, including 73 genomes generated for this study, to disentangle the genetic mechanisms underlying local adaptation of domestic mammals. Although molecular convergence is comparatively rare at the DNA sequence level, we found convergent signature of positive selection at the gene level, particularly the EPAS1 gene in these Tibetan domestic mammals. We also reported a potential function in response to hypoxia for the gene C10orf67, which underwent positive selection in three of the domestic mammals. Our data provide an insight into adaptive evolution of high-altitude domestic mammals, and should facilitate the search for additional novel genes involved in the hypoxia response pathway.     

Size-dependent trajectories of DNA macromolecules due to insulative dielectrophoresis in submicrometer-deep fluidic channels

In this paper, we demonstrate for the first time that insulative dielectrophoresis can induce size-dependent trajectories of DNA macromolecules. We experimentally use λ (48.5 kbp) and T4GT7 (165.6 kbp) DNA molecules flowing continuously around a sharp corner inside fluidic channels with a depth of 0.4 μm. Numerical simulation of the electrokinetic force distribution inside the channels is in qualitative agreement with our experimentally observed trajectories. We discuss a possible physical mechanism for the DNA polarization and dielectrophoresis inside confining channels, based on the observed dielectrophoresis responses due to different DNA sizes and various electric fields applied between the inlet and the outlet. The proposed physical mechanism indicates that further extensive investigations, both theoretically and experimentally, would be very useful to better elucidate the forces involved at DNA dielectrophoresis. When applied for size-based sorting of DNA molecules, our sorting method offers two major advantages compared to earlier attempts with insulative dielectrophoresis: Its continuous operation allows for high-throughput analysis, and it only requires electric field strengths as low as ∼10 V∕cm.     

A comparative study on oxidative stress and antioxidant status in ischemic stroke patients with and without diabetes

The study was conducted to find out the extent of lipid peroxidation and antioxidant status in ischemic stroke patients (ISPs) with and without diabetes. Malondialdehyde (MDA) was studied as a marker of lipid peroxidation. Glutathione (GSH), uric acid and ceruloplasmin were estimated to study the antioxidant potential of ISPs. Significantly higher levels of MDA were found in both the groups of ISPs and the increase in MDA was more in ISPs without diabetes. GSH levels were decreased significantly in both the groups of ISPs and maximum decline was found in ISPs with diabetes. Uric acid levels were significantly increased in both the groups of ISPs. Ceruloplasmin levels were increased significantly in ISPs without diabetes, whereas its levels were slightly decreased in ISPs with diabetes. A negative correlation was found between MDA and the antioxidants GSH, uric acid and ceruloplasmin in ISPs with diabetes. This study suggests that there is an association between ischemic stroke and increased oxidative stress and the antioxidant potential is impaired in both the groups of ISPs with and without diabetes.     

Pre-service teachers’ attempts at debating contemporary issues in science education: A case study from Botswana

This paper constitutes an attempt to explore trends, issues and challenges that emerge when three different cohorts of pre-service teachers debate contemporary issues in science education at the University of Botswana. Apart from the author's experience of teaching the course, the impetus for this study also comes from a growing interest in the contemporary literature in the need for teachers who, in the context of globalization and knowledge economy, are ‘self-reforming’ through continually addressing the key issues of their profession. Unfortunately, the current situation is such that this burden of interrogation falls heaviest on teachers, despite their lack of skills in undertaking the task.     

“Because if we don’t talk about it,how are we going to prevent it?”: Lucidity,a narrative-based digital game about sexual violence

This paper describes the development and evaluation of an interactive, narrative-based, multimedia game to promote learning and communication about sexual violence and health topics. High school-aged participants created the game concept in a three-week workshop, after which assets were assembled and refined by a university-based game design lab. The outcome, Lucidity, was a multimedia game with a nonlinear narrative that led to two different outcomes based on player decisions. The narrative followed the life of one character, an African American woman named Zaria who remembers and grapples with a sexual assault from her past. The player discovers parts of the story by reading comics, watching videos, navigating interactive websites and playing short videogames. The final evaluation consisted of gameplay, a post-game focus group and follow-up interviews. Twenty-four young people participated in three focus group discussions (n = 9, n = 5, n = 10); 23 participated in the follow-up interviews. Salient themes identified in the focus group discussions included: overall approval of the game, the acquisition of new knowledge and minimal past exposure to conversations or education about sexual violence. At follow-up, almost all (n = 22) had initiated a conversation about sexual violence with a parent, peer and/or teacher. Lucidity succeeded in engaging young people and facilitating communication with adults and peers regarding sexual violence and other sexual health topics. Ultimately, a game-based intervention such as this represents a feasible approach for introducing issues of sexual violence, with potential for future implementation in educational settings.     

Classifying the Context Clues in Children's Text

This study aimed to determine which types of context clues exist in children's texts and whether it is possible for experts to identify reliably those clues. Three experienced coders used Ames’ clue set as a foundation for a system to classify context clues in children's text. Findings showed that the adjustments to Ames’ system resulted in 15 clues that can be used to capture the majority of clues found in children narrative and expository text. This study adds to the limited empirically validated systems available for classifying different context clues. A usable classification of context clues has application to reading research that considers or controls for text factors as well as teaching reading strategies in K–12 classrooms.     

Stress in Families of Young Children with Down Syndrome, Williams Syndrome, and Smith-Magenis Syndrome

This study examined whether stress levels differ in families of young children with three different genetic etiologies of mental retardation, and whether child characteristics associated with those genetic etiologies may help explain these differences. Participants were sixty families of young children with Down syndrome, Williams syndrome, and Smith-Magenis syndrome. All children were between the ages of 3 and 10 years. Parents completed Achenbach's Child Behavior Checklist, the Questionnaire on Resources and Stress-Friedrich edition, and a demographic questionnaire. Families of children with Down syndrome experienced significantly less Pessimism than the other two etiology groups and significantly less Parent and Family Problems than families of children with Smith-Magenis syndrome. The strongest predictor of Parent and Family Problems was maladaptive behavior in Smith-Magenis syndrome, younger age in Down syndrome, and both maladaptive behavior and younger age in Williams syndrome. Maladaptive behavior predicted Pessimism in families of children with Smith-Magenis syndrome, but none of the variables examined significantly predicted Pessimism in the other two syndromes. The importance of behavioral phenotype research is discussed for practitioners working with young children with mental retardation and their families.