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Node-Pore Sensing, NPS, is an extremely versatile and powerful technique for the analysis of cells and the detection of extracellular vesicles (EVs). NPS involves measuring the modulated current pulse caused by a cell transiting a microfluidic channel that has been segmented by a series of inserted nodes. As the current pulse reflects the number of nodes and segments of the channel, NPS can achieve exquisite sensitivity. Thus, when used as a Coulter counter, NPS can measure the sub-micron size increase of antibody-coated colloids to which EVs are specifically bound. By simply inserting between two nodes a contraction channel through which cells can squeeze, one can mechanically phenotype cells. We discuss the details of performing these two NPS applications.

Viscoelastic properties of cells provide valuable information regarding biological or clinically relevant cellular characteristics. Here, we introduce a new, electronic-based, microfluidic platform-visco-node-pore sensing (visco-NPS)-which quantifies cellular viscoelastic properties under periodic deformation. We measure the storage (G) and loss (G″) moduli (i.e., elasticity and viscosity, respectively) of cells. By applying a wide range of deformation frequencies, our platform quantifies the frequency dependence of viscoelastic properties. G and G″ measurements show that the viscoelastic properties of malignant breast epithelial cells (MCF-7) are distinctly different from those of non-malignant breast epithelial cells (MCF-10A). With its sensitivity, visco-NPS can dissect the individual contributions of different cytoskeletal components to whole-cell mechanical properties. Moreover, visco-NPS can quantify the mechanical transitions of cells as they traverse the cell cycle or are initiated into an epithelial-mesenchymal transition. Visco-NPS identifies viscoelastic characteristics of cell populations, providing a biophysical understanding of cellular behavior and a potential for clinical applications.

Advancements in microfluidic technologies have led to the development of many new tools for both the characterization and sorting of single cells without the need for exogenous labels. Label-free microfluidics reduce the preparation time, reagents needed, and cost of conventional methods based on fluorescent or magnetic labels. Furthermore, these devices enable analysis of cell properties such as mechanical phenotype and dielectric parameters that cannot be characterized with traditional labels. Some of the most promising technologies for current and future development toward label-free, single-cell analysis and sorting include electronic sensors such as Coulter counters and electrical impedance cytometry; deformation analysis using optical traps and deformation cytometry; hydrodynamic sorting such as deterministic lateral displacement, inertial focusing, and microvortex trapping; and acoustic sorting using traveling or standing surface acoustic waves. These label-free microfluidic methods have been used to screen, sort, and analyze cells for a wide range of biomedical and clinical applications, including cell cycle monitoring, rapid complete blood counts, cancer diagnosis, metastatic progression monitoring, HIV and parasite detection, circulating tumor cell isolation, and point-of-care diagnostics. Because of the versatility of label-free methods for characterization and sorting, the low-cost nature of microfluidics, and the rapid prototyping capabilities of modern microfabrication, we expect this class of technology to continue to be an area of high research interest going forward. New developments in this field will contribute to the ongoing paradigm shift in cell analysis and sorting technologies toward label-free microfluidic devices, enabling new capabilities in biomedical research tools as well as clinical diagnostics. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > Diagnostic Nanodevices.

We report abrupt Te doping of GaInP solar cells grown by molecular beam epitaxy (MBE) through the use of a low substrate temperature of 420 °C and subsequent elimination of surface segregation. First, a Te surface pre-dose layer and reduced substrate temperature were required to achieve abrupt profiles at doping >1 × 1018 cm−3 in calibration samples, while reduced doping of 5.7 × 1017 cm−3 did not require the surface layer. Next, we demonstrate front-junction n+/p GaInP cells with an improved internal quantum efficiency (IQE) after Te doping of the n-type emitter directly attributable to an ∼2.5× higher carrier diffusion length, with IQE-derived short-circuit current density increasing from 13.2 to 14.1 mA/cm2. Rapid thermal annealing further boosted the performance through improvements in the minority carrier lifetime of the p-GaInP base. The use of low substrate temperature in MBE-grown GaInP enables abrupt Te doping profiles to be attained in a straightforward manner and is promising for both solar cells and tunnel junctions. [ABSTRACT FROM AUTHOR]

III-V lasers based on self-assembled quantum dots (QDs) have attracted widespread interest due to their unique characteristics, including low threshold current density (Jth), low sensitivity to backreflections, and resistance to threading dislocations. While most work to date has focused on 1.3 μm InAs/GaAs QDs, InP QDs have also aroused interest in lasers emitting at visible wavelengths. Molecular beam epitaxy (MBE) enables the growth of high-density InP/AlGaInP QDs on exact (001)-oriented GaAs substrates but requires a relatively low substrate temperature of <500 °C. The low substrate temperature used for phosphide growth in MBE leads to degraded optical properties and makes post-growth annealing a crucial step to improve the optical quality. Here, we report the exceptional thermal stability of InP/AlGaInP QDs grown using MBE, with up to 50× improvement in room temperature photoluminescence intensity with the optimization of annealing temperature and time. We also demonstrate the room temperature pulsed operation of InP multiple quantum dot (MQD) lasers on GaAs (001) emitting close to 735 nm with Jth values of 499 A/cm2 after annealing, a factor of 6 lower than their as-grown counterparts and comparable to such devices grown by MOCVD. In0.6Ga0.4P single quantum well (SQW) lasers on GaAs (001) also exhibit a substantial reduction in Jth from 340 A/cm2 as-grown to 200 A/cm2 after annealing, emitting at 680 nm under pulsed operation conditions. This work shows that post-growth annealing is essential for realizing record-performance phosphide lasers on GaAs grown by MBE for applications in visible photonics. [ABSTRACT FROM AUTHOR]

Analysis of hematopoietic stem cell function in nonhuman primates provides insights that are relevant for human biology and therapeutic strategies. In this study, we applied quantitative genetic barcoding to track the clonal output of transplanted autologous rhesus macaque hematopoietic stem and progenitor cells over a time period of up to 9.5 months. We found that unilineage short-term progenitors reconstituted myeloid and lymphoid lineages at 1 month but were supplanted over time by multilineage clones, initially myeloid restricted, then myeloid-B clones, and then stable myeloid-B-T multilineage, long-term repopulating clones. Surprisingly, reconstitution of the natural killer (NK) cell lineage, and particularly the major CD16(+)/CD56(-) peripheral blood NK compartment, showed limited clonal overlap with T, B, or myeloid lineages, and therefore appears to be ontologically distinct. Thus, in addition to providing insights into clonal behavior over time, our analysis suggests an unexpected paradigm for the relationship between NK cells and other hematopoietic lineages in primates.

Music is an integral part of culture and human societies, which anthropologists study. What makes music so potent is its ability to contain values, reflect perspectives, and fill niches of societal needs. In this paper, I will discuss how ethnomusicology aids scholars in a deeper understanding of contexts, perspectives, and values in music and the experiences of the people who created it. I will analyze the relationships between music and technique, ritual, and religion in seven case studies. Drawing from examples from "right" singing in Estonia, the choral works of Stravinsky, Ambonwari rituals, ritual wailing in Amerindian Brazil, the maqam, syncretism in Southeast Asia, and Tamil Christian religious music, I will show how ethnomusicology uncovers understanding of the cosmology, values, and socio-cultural interactions of a people and their culture. [ABSTRACT FROM AUTHOR]