263 research outputs found
A Whole New World: PreK-12 Teachers\u27 Perceptions of Instruction during a Pandemic
This manuscript explores educators’ perceptions about professional and personal challenges and successes with virtual instruction, along with their concerns about the impact on students and student learning in a virtual environment during the COVID-19 pandemic. Teachers from seventeen school systems in Tennessee and Alabama were invited to participate in the study with sixty-seven participants completing surveys. A phenomenology design model was used, and In Vivo Coding was conducted to analyze the data. Results revealed four main themes related to teachers’ experiences with virtual learning: personal perceptions, instruction, impact on students, and communication. Discussion of the results and their implications are addressed along with limitations and recommendations for future research
Mesenchymal stem cells protect against obstruction-induced renal fibrosis by decreasing STAT3 activation and STAT3-dependent MMP-9 production
STAT3 is a transcription factor implicated in renal fibrotic injury, but the role of STAT3 in mesenchymal stem cell (MSC)-induced renoprotection during renal fibrosis remains unknown. We hypothesized that MSCs protect against obstruction-induced renal fibrosis by downregulating STAT3 activation and STAT3-induced matrix metalloproteinase-9 (MMP-9) expression. Male Sprague-Dawley rats underwent renal arterial injection of vehicle or MSCs (1 × 106/rat) immediately before sham operation or induction of unilateral ureteral obstruction (UUO). The kidneys were harvested after 4 wk and analyzed for collagen I and III gene expression, collagen deposition (Masson's trichrome), fibronectin, α-smooth muscle actin, active STAT3 (p-STAT3), MMP-9, and tissue inhibitor of matrix metalloproteinases 1 (TIMP-1) expression. In a separate arm, the STAT3 inhibitor S3I-201 (10 mg/kg) vs. vehicle was administered to rats intraperitoneally just after induction of UUO and daily for 14 days thereafter. The kidneys were harvested after 2 wk and analyzed for p-STAT3 and MMP-9 expression, and collagen and fibronectin deposition. Renal obstruction induced a significant increase in collagen, fibronectin, α-SMA, p-STAT3, MMP-9, and TIMP-1 expression while exogenously administered MSCs significantly reduced these indicators of obstruction-induced renal fibrosis. STAT3 inhibition with S3I-201 significantly reduced obstruction-induced MMP-9 expression and tubulointerstitial fibrosis. These results demonstrate that MSCs protect against obstruction-induced renal fibrosis, in part, by decreasing STAT3 activation and STAT3-dependent MMP-9 production
Optimal control with a multidimensional quantum invariant
Optimal quantum control of continuous variable systems poses a formidable
computational challenge because of the high-dimensional character of the system
dynamics. The framework of quantum invariants can significantly reduce the
complexity of such problems, but it requires the knowledge of an invariant
compatible with the Hamiltonian of the system in question. We explore the
potential of a Gaussian invariant that is suitable for quadratic Hamiltonians
with any given number of motional degrees of freedom for quantum optimal
control problems that are inspired by current challenges in
ground-state-to-ground-state shuttling of trapped-ions.Comment: 9 pages, 4 figure
Quadratic solitons in cubic crystals
Starting from the Maxwell's equations and without resort to the paraxial
approximation, we derive equations describing stationary (1+1)-dimensional
beams propagating at an arbitrary direction in an optical crystal with cubic
symmetry and purely quadratic nonlinearity. The equations are derived
separately for beams with the TE and TM polarizations. In both cases, they
contain and cubic nonlinear terms, the latter ones generated via the cascading
mechanism. The final TE equations and soliton solutions to them are quite
similar to those in previously known models with mixed quadratic-cubic
nonlinearities. On the contrary to this, the TM model is very different from
previously known ones. It consists of four first-order equations for transverse
and longitudinal components of the electric field at the fundamental and second
harmonics. Fundamental-soliton solutions of the TM model are also drastically
different from the usual "quadratic" solitons, in terms of the parity of their
components. In particular, the transverse and longitudinal components of the
electric field at the fundamental harmonic in the fundamental TM solitons are
described, respectively, by odd and single-humped even functions of the
transverse coordinate. Amplitudes of the longitudinal and transverse fields
become comparable for very narrow solitons, whose width is commensurate to the
carrier wavelength.Comment: Optics Communications, in pres
Monetary discounting and ventral striatal dopamine receptor availability in nontreatment-seeking alcoholics and social drinkers
RATIONALE: Dopamine (DA) in the ventral striatum (VST) has long been implicated in addiction pathologies, yet its role in temporal decision-making is not well-understood.
OBJECTIVES: To determine if VST DA D2 receptor availability corresponds with greater impulsive choice in both nontreatment-seeking alcoholics (NTS) and social drinkers (SD).
METHODS: NTS subjects (n = 10) and SD (n = 13) received PET scans at baseline with the D2/D3 radioligand [(11)C]raclopride (RAC). Outside the scanner, subjects performed a delay discounting procedure with monetary rewards. RAC binding potential (BPND) was estimated voxelwise, and correlations were performed to test for relationships between VST BPND and delay discounting performance. Self-reported impulsivity was also tested for correlations with BPND.
RESULTS: Across all subjects, greater impulsive choice for $20 correlated with lower BPND in the right VST. NTS showed greater impulsive choice than SD and were more impulsive by self-report. Across all subjects, the capacity of larger rewards to reduce impulsive choice (the magnitude effect) correlated negatively (p = 0.028) with problematic alcohol use (AUDIT) scores. Self-reported impulsivity did not correlate with BPND in VST.
CONCLUSIONS: Preference for immediate reinforcement may reflect greater endogenous striatal DA or lower D2 number, or both. Alcoholic status did not mediate significant effects on VST BPND, suggesting minimal effects from alcohol exposure. The apparent lack of BPND correlation with self-reported impulsivity highlights the need for objective behavioral assays in the study of the neurochemical substrates of behavior. Finally, our results suggest that the magnitude effect may be more sensitive to alcohol-induced problems than single discounting measures
Extracting inter-dot tunnel couplings between few donor quantum dots in silicon
The long term scaling prospects for solid-state quantum computing architectures relies heavily on the
ability to simply and reliably measure and control the coherent electron interaction strength, known
as the tunnel coupling, tc. Here, we describe a method to extract the tc between two quantum dots
(QDs) utilising their different tunnel rates to a reservoir. We demonstrate the technique on a few
donor triple QD tunnel coupled to a nearby single-electron transistor(SET)in silicon. The device was
patterned using scanning tunneling microscopy-hydrogen lithography allowing for a direct
measurement of the tunnel coupling for a given inter-dot distance. We extract tc = ± 5.5 1.8 GHz
and tc = ± 2.2 1.3 GHz between each of the nearest-neighbour QDs which are separated by 14.5 nm
and 14.0 nm, respectively. The technique allows for an accurate measurement of tc for nanoscale
devices even when it is smaller than the electron temperature and is an ideal characterisation tool for
multi-dot systems with a charge senso
IL-18 neutralization ameliorates obstruction-induced epithelial–mesenchymal transition and renal fibrosis
Ureteral obstruction results in renal fibrosis in part due to inflammatory injury. The role of interleukin-18 (IL-18), an important mediator of inflammation, in the genesis of renal fibrosis was studied using transgenic mice overexpressing human IL-18-binding protein. In addition, HK-2 cells were analyzed following direct exposure to IL-18 compared to control media. Two weeks after ureteral obstruction, the kidneys of wild-type mice had a significant increase in IL-18 production, collagen deposition, α-smooth muscle actin and RhoA expression, fibroblast and macrophage accumulation, chemokine expression, and transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α) production, whereas E-cadherin expression was simultaneously decreased. The transgenic mice with neutralized IL-18 activity exhibited significant reductions in these indicators of obstruction-induced renal fibrosis and epithelial– mesenchymal transition, without demonstrating alterations in TGF-β1 or TNF-α activity. Similarly, the HK-2 cells exhibited increased α-smooth muscle actin expression and collagen production, and decreased E-cadherin expression in response to IL-18 stimulation without alterations in TNF-α or TGF-β1 activity. Our study demonstrates that IL-18 is a significant mediator of obstruction-induced renal fibrosis and epithelial– mesenchymal transition independent of downstream TGF-β1 or TNF-α production
Tunneling statistics for analysis of spin-readout fidelity
We investigate spin and charge dynamics of a quantum dot of phosphorus atoms
coupled to a radio-frequency single-electron transistor (rf-SET) using full
counting statistics. We show how the magnetic field plays a role in determining
the bunching or anti-bunching tunnelling statistics of the donor dot and SET
system. Using the counting statistics we show how to determine the lowest
magnetic field where spin-readout is possible. We then show how such a
measurement can be used to investigate and optimise single electron
spin-readout fidelity.Comment: 11 pages, 6 figure
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