| 1. |
- Beal, Jacob, et al.
(författare)
-
Robust estimation of bacterial cell count from optical density
- 2020
-
Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
|
|
| 2. |
- Han, Duo, et al.
(författare)
-
An Opportunistic Sensor Scheduling Solution to Remote State Estimation Over Multiple Channels
- 2016
-
Ingår i: IEEE Transactions on Signal Processing. - : IEEE Press. - 1053-587X .- 1941-0476. ; 64:18, s. 4905-4917
-
Tidskriftsartikel (refereegranskat)abstract
- We consider a sensor scheduling problem where the sensors have multiple choices of communication channel to send their local measurements to a remote state estimator for state estimation. Specifically, the sensors can transmit high-precision data packets over an expensive channel or low-precision data packets, which are quantized in several bits, over some cheap channels. The expensive channel, though being able to deliver more accurate data which leads to good estimation quality at the remote estimator, can only be used scarcely due to its high cost (e.g., high energy consumption). On the other hand, the cheap channel, though having a small cost, delivers less accurate data which inevitably deteriorates the remote estimation quality. In this work we propose a new framework in which the sensors switch between the two channels to achieve a better tradeoff among the communication cost, the estimation performance and the computational complexity, where the two-channel case can be easily extended to a multiple-channel case. We propose an opportunistic sensor schedule which reduces the communication cost by randomly switching among the expensive and cheap channels, and in the meantime maintains low computational complexity while introducing data quantization into the estimation problem. We present a minimum mean square error (MMSE) estimator in a closed-form under the proposed opportunistic sensor schedule. We also formulate an optimization problem to search the best opportunistic schedule with a linear quantizer. Furthermore, we show that the MMSE estimator in the limiting case becomes the standard Kalman filter.
|
|
| 3. |
- Han, Duo, et al.
(författare)
-
Stochastic Sensor Scheduling for Multiple Dynamical Processes over a Shared Channel
- 2016
-
Ingår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016. - : IEEE. - 9781509018376 ; , s. 6315-6320
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of multiple sensor scheduling for remote state estimation over a shared link. A number of sensors monitor different dynamical processes simultaneously but only one sensor can access the shared channel at each time instant to transmit the data packet to the estimator. We propose a stochastic event-based sensor scheduling framework in which each sensor makes transmission decisions based on both the channel accessibility and the self event-triggering condition. The corresponding optimal estimator is explicitly given. By ultilizing the realtime information, the proposed schedule is shown to be a generalization of the time based ones and outperform the time-based ones in terms of the estimation quality. By formulating an Markov decision process (MDP) problem with average cost criterion, we can find the optimal parameters for the event-based schedule. For practical use, we also design a simple suboptimal schedule to mitigate the computational complexity of solving an MDP problem. We also propose a method to quantify the optimality gap for any suboptimal schedules.
|
|
| 4. |
- Han, Yilin, et al.
(författare)
-
171 Scandium-based full Heusler compounds : A comprehensive study of competition between XA and L21 atomic ordering
- 2019
-
Ingår i: Results in Physics. - : Elsevier. - 2211-3797. ; 12, s. 435-446
-
Tidskriftsartikel (refereegranskat)abstract
- The site-preference rule (SPR), which is widely used to design and study the properties of full-Heusler alloys X2YZ, is applied to determine the positions of different transition-metal elements with various numbers of valence electrons in Heusler alloys. The scandium-based full Heusler alloys should form an XA structure according to the SPR, because the transition-metal element Sc with fewer valence electrons tends to occupy the Wyckoff sites A(0, 0, 0) and B(0.25, 0.25, 0.25). As opposed to previous investigations, L21-type scandium-based full Heusler alloys, which do not follow the SPR, are also considered in this work. Theoretical computations are used to study the atomic-site preferences of 171 scandium-based full Heusler alloys, and the results indicate that most of these alloys form L21-type structures rather than XA-type structures. Two possible orderings are also studied in terms of their difference in charge density. Furthermore, the ground state, electronic structure, and magnetic characteristics of these alloys are also investigated in detail in both XA and L21 structures. The results reveal dramatic differences between XA- and L21-type alloys. This study thus presents a counterexample of the SPR rule and should provide significant guidance for the future design of full-Heusler alloys.
|
|
| 5. |
- Han, Yilin, et al.
(författare)
-
Effect of scaffold properties on adhesion and maintenance of boundary cap neural crest stem cells in vitro
- 2020
-
Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 108:6, s. 1274-1280
-
Tidskriftsartikel (refereegranskat)abstract
- Optimal combination of stem cells and biocompatible support material is a promising strategy for successful tissue engineering. The required differentiation of stem cells is crucial for functionality of engineered tissues and can be regulated by chemical and physical cues. Here we examined how boundary cap neural crest stem cells (bNCSCs) are affected when cultured in the same medium, but on collagen- or laminin-polyacrylamide (PAA) scaffolds of different stiffness (0.5, 1, or similar to 7 kPa). bNCSCs displayed marked differences in their ability to attach, maintain a large cell population and differentiate, depending on scaffold stiffness. These findings show that the design of physical cues is an important parameter to achieve optimal stem cell properties for tissue repair and engineering.
|
|
| 6. |
- Han, Yilin, et al.
(författare)
-
Effects of microgravity on neural crest stem cells
- 2024
-
Ingår i: Frontiers in Neuroscience. - : Frontiers Media S.A.. - 1662-4548 .- 1662-453X. ; 18
-
Tidskriftsartikel (refereegranskat)abstract
- Exposure to microgravity (μg) results in a range of systemic changes in the organism, but may also have beneficial cellular effects. In a previous study we detected increased proliferation capacity and upregulation of genes related to proliferation and survival in boundary cap neural crest stem cells (BC) after MASER14 sounding rocket flight compared to ground-based controls. However, whether these changes were due to μg or hypergravity was not clarified. In the current MASER15 experiment BCs were exposed simultaneously to μg and 1 g conditions provided by an onboard centrifuge. BCs exposed to μg displayed a markedly increased proliferation capacity compared to 1 g on board controls, and genetic analysis of BCs harvested 5 h after flight revealed an upregulation, specifically in μg-exposed BCs, of Zfp462 transcription factor, a key regulator of cell pluripotency and neuronal fate. This was associated with alterations in exosome microRNA content between μg and 1 g exposed MASER15 specimens. Since the specimens from MASER14 were obtained for analysis with 1 week’s delay, we examined whether gene expression and exosome content were different compared to the current MASER15 experiments, in which specimens were harvested 5 h after flight. The overall pattern of gene expression was different and Zfp462 expression was down-regulated in MASER14 BC μg compared to directly harvested specimens (MASER15). MicroRNA exosome content was markedly altered in medium harvested with delay compared to directly collected samples. In conclusion, our analysis indicates that even short exposure to μg alters gene expression, leading to increased BC capacity for proliferation and survival, lasting for a long time after μg exposure. With delayed harvest of specimens, a situation which may occur due to special post-flight circumstances, the exosome microRNA content is modified compared to fast specimen harvest, and the direct effects from μg exposure may be partially attenuated, whereas other effects can last for a long time after return to ground conditions.
|
|
| 7. |
- Han, Yilin, et al.
(författare)
-
Molecular genetic analysis of neural stem cells after space flight and simulated microgravity on earth
- 2021
-
Ingår i: Biotechnology and Bioengineering. - : John Wiley & Sons. - 0006-3592 .- 1097-0290. ; 118:10, s. 3832-3846
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding how stem cells adapt to space flight conditions is fundamental for human space missions and extraterrestrial settlement. We analyzed gene expression in boundary cap neural crest stem cells (BCs), which are attractive for regenerative medicine by their ability to promote proliferation and survival of cocultured and co-implanted cells. BCs were launched to space (space exposed cells) (SEC), onboard sounding rocket MASER 14 as free-floating neurospheres or in a bioprinted scaffold. For comparison, BCs were placed in a random positioning machine (RPM) to simulate microgravity on earth (RPM cells) or were cultured under control conditions in the laboratory. Using next-generation RNA sequencing and data post-processing, we discovered that SEC upregulated genes related to proliferation and survival, whereas RPM cells upregulated genes associated with differentiation and inflammation. Thus, (i) space flight provides unique conditions with distinctly different effects on the properties of BC compared to earth controls, and (ii) the space flight exposure induces postflight properties that reinforce the utility of BC for regenerative medicine and tissue engineering.
|
|
| 8. |
- Han, YeDuo, et al.
(författare)
-
On Stochastic Sensor Network Scheduling for Multiple Processes
- 2017
-
Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 62:12, s. 6633-6640
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of multiple sensor scheduling for remote state estimation of multiple process over a shared link. In this problem, a set of sensors monitor mutually independent dynamical systems in parallel but only one sensor can access the shared channel at each time to transmit the data packet to the estimator. We propose a stochastic event-based sensor scheduling in which each sensor makes transmission decisions based on both channel accessibility and distributed event-triggering conditions. The corresponding minimum mean squared error estimator is explicitly given. Considering information patterns accessed by sensor schedulers, time-based ones can be treated as a special case of the proposed one. By ultilizing real-time information, the proposed schedule outperforms the time-based ones in terms of the estimation quality. Resorting to solving a Markov decision process (MDP) problem with an average cost criterion, we can find optimal parameters for the proposed schedule. As for practical use, a greedy algorithm is devised for parameter design, which has rather low computational complexity. We also provide a method to quantify the performance gap between the schedule optimized via MDP and any other schedules.
|
|
| 9. |
- Han, Yilin, et al.
(författare)
-
Towards 3D Bioprinted Spinal Cord Organoids
- 2022
-
Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 23:10
-
Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional (3D) cultures, so-called organoids, have emerged as an attractive tool for disease modeling and therapeutic innovations. Here, we aim to determine if boundary cap neural crest stem cells (BC) can survive and differentiate in gelatin-based 3D bioprinted bioink scaffolds in order to establish an enabling technology for the fabrication of spinal cord organoids on a chip. BC previously demonstrated the ability to support survival and differentiation of co-implanted or co-cultured cells and supported motor neuron survival in excitotoxically challenged spinal cord slice cultures. We tested different combinations of bioink and cross-linked material, analyzed the survival of BC on the surface and inside the scaffolds, and then tested if human iPSC-derived neural cells (motor neuron precursors and astrocytes) can be printed with the same protocol, which was developed for BC. We showed that this protocol is applicable for human cells. Neural differentiation was more prominent in the peripheral compared to central parts of the printed construct, presumably because of easier access to differentiation-promoting factors in the medium. These findings show that the gelatin-based and enzymatically cross-linked hydrogel is a suitable bioink for building a multicellular, bioprinted spinal cord organoid, but that further measures are still required to achieve uniform neural differentiation.
|
|
| 10. |
- Omelyanchik, Alexander, et al.
(författare)
-
Boosting Magnetoelectric Effect in Polymer-Based Nanocomposites
- 2021
-
Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:5
-
Tidskriftsartikel (refereegranskat)abstract
- Polymer-based magnetoelectric composite materials have attracted a lot of attention due to their high potential in various types of applications as magnetic field sensors, energy harvesting, and biomedical devices. Current researches are focused on the increase in the efficiency of magnetoelectric transformation. In this work, a new strategy of arrangement of clusters of magnetic nanoparticles by an external magnetic field in PVDF and PFVD-TrFE matrixes is proposed to increase the voltage coefficient (alpha ME) of the magnetoelectric effect. Another strategy is the use of 3-component composites through the inclusion of piezoelectric BaTiO3 particles. Developed strategies allow us to increase the alpha ME value from similar to 5 mV/cm.Oe for the composite of randomly distributed CoFe2O4 nanoparticles in PVDF matrix to similar to 18.5 mV/cm.Oe for a composite of magnetic particles in PVDF-TrFE matrix with 5%wt of piezoelectric particles. The applicability of such materials as bioactive surface is demonstrated on neural crest stem cell cultures.
|
|
| 11. |
- Trolle, Carl, 1985-, et al.
(författare)
-
Boundary cap neural crest stem cells promote angiogenesis after transplantation to avulsed dorsal roots in mice and induce migration of endothelial cells in 3D printed scaffolds
- 2024
-
Ingår i: Neuroscience Letters. - : Elsevier. - 0304-3940 .- 1872-7972. ; 826
-
Tidskriftsartikel (refereegranskat)abstract
- Dorsal root avulsion injuries lead to loss of sensation and to reorganization of blood vessels (BVs) in the injured area. The inability of injured sensory axons to re-enter the spinal cord results in permanent loss of sensation, and often also leads to the development of neuropathic pain. Approaches that restore connection between peripheral sensory axons and their CNS targets are thus urgently need. Previous research has shown that sensory axons from peripherally grafted human sensory neurons are able to enter the spinal cord by growing along BVs which penetrate the CNS from the spinal cord surface. In this study we analysed the distribution of BVs after avulsion injury and how their pattern is affected by implantation at the injury site of boundary cap neural crest stem cells (bNCSCs), a transient cluster of cells, which are located at the boundary between the spinal cord and peripheral nervous system and assist the growth of sensory axons from periphery into the spinal cord during development. The superficial dorsal spinal cord vasculature was examined using intravital microscopy and intravascular BV labelling. bNCSC transplantation increased vascular volume in a non-dose responsive manner, whereas dorsal root avulsion alone did not decrease the vascular volume. To determine whether bNCSC are endowed with angiogenic properties we prepared 3D printed scaffolds, containing bNCSCs together with rings prepared from mouse aorta. We show that bNCSC do induce migration and assembly of endothelial cells in this system. These findings suggest that bNCSC transplant can promote vascularization in vivo and contribute to BV formation in 3D printed scaffolds.
|
|
| 12. |
- Wu, Mengxin, et al.
(författare)
-
Site preference and tetragonal distortion inpalladium-rich Heusler alloys
- 2019
-
Ingår i: IUCrJ. - Chester : International Union of Crystallography (IUCr). - 2052-2525. ; 6, s. 218-225
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, two kinds of competition between different Heusler structure types are considered, one is the competition between XA and L2(1) structures based on the cubic system of full-Heusler alloys, Pd(2)YZ (Y = Co, Fe, Mn; Z = B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb). Most alloys prefer the L2(1) structure; that is, Pd atoms tend to occupy the a (0, 0, 0) and c (0.5, 0.5, 0.5) Wyckoff sites, the Y atom is generally located at site b (0.25, 0.25, 0.25), and the main group element Z has a preference for site d (0.75, 0.75, 0.75), meeting the well known site-preference rule. The difference between these two cubic structures in terms of their magnetic and electronic properties is illustrated further by their phonon dispersion and density-of-states curves. The second type of competition that was subjected to systematic study was the competitive mechanism between the L2(1 )cubic system and its L1(0) tetragonal system. A series of potential tetragonal distortions in cubic full-Heusler alloys (Pd(2)YZ) have been predicted in this work. The valley-and-peak structure at, or in the vicinity of, the Fermi level in both spin channels is mainly attributed to the tetragonal ground states according to the density-of-states analysis. Delta E-M is defined as the difference between the most stable energy values of the cubic and tetragonal states; the larger the value, the easier the occurrence of tetragonal distortion, and the corresponding tetragonal structure is stable. Compared with the Delta E-M values of classic Mn-2 based tetragonal Heusler alloys, the Delta E(M )values of most Pd(2)CoZ alloys in this study indicate that they can overcome the energy barriers between cubic and tetragonal states, and possess possible tetragonal transformations. The uniform strain has also been taken into consideration to further investigate the tetragonal distortion of these alloys in detail. This work aims to provide guidance for researchers to further explore and study new magnetic functional tetragonal materials among the full-Heusler alloys.
|
|
