1,805 research outputs found
Continuous ASL perfusion fMRI investigation of higher cognition: Quantification of tonic CBF changes during sustained attention and working memory tasks
Arterial spin labeling (ASL) perfusion fMRI is an emerging method in clinical neuroimaging. Its non-invasiveness, absence of low frequency noise, and ability to quantify the absolute level of cerebral blood flow (CBF) make the method ideal for longitudinal designs or low frequency paradigms. Despite the usefulness in the study of cognitive dysfunctions in clinical populations, perfusion activation studies to date have been conducted for simple sensorimotor paradigms or with single-slice acquisition, mainly due to technical challenges. Using our recently developed amplitude-modulated continuous ASL (CASL) perfusion fMRI protocol, we assessed the feasibility of a higher level cognitive activation study in twelve healthy subjects. Taking advantage of the ASL noise properties, we were able to study tonic CBF changes during uninterrupted 6-min continuous performance of working memory and sustained attention tasks. For the visual sustained attention task, regional CBF increases (6–12 ml/100 g/min) were detected in the right middle frontal gyrus, the bilateral occipital gyri, and the anterior cingulate/medial frontal gyri. During the 2-back working memory task, significantly increased activations (7–11 ml/100 g/min) were found in the left inferior frontal/precentral gyri, the left inferior parietal lobule, the anterior cingulate/medial frontal gyri, and the left occipital gyrus. Locations of activated and deactivated areas largely concur with previous PET and BOLD fMRI studies utilizing similar paradigms. These results demonstrate that CASL perfusion fMRI can be successfully utilized for the investigation of the tonic CBF changes associated with high level cognitive operations. Increased applications of the method to the investigation of cognitively impaired populations are expected to follow
Hole doping in compositionally complex correlated oxide enables tunable exchange biasing
Magnetic interfaces and the phenomena arising from them drive both the design
of modern spintronics and fundamental research. Recently, it was revealed that
through designing magnetic frustration in configurationally complex entropy
stabilized oxides, exchange bias can occur in structurally single crystal
films. This eliminates the need for complex heterostructures and nanocomposites
in the design and control of magnetic response phenomena. In this work, we
demonstrate through hole doping of a high entropy perovskite oxide that tuning
of magnetic responses can be achieved. With detailed magnetometry, we show
magnetic coupling exhibiting a variety of magnetic responses including exchange
bias and antiferromagnetic spin reversal in the entropy stabilized ABO3
perovskite oxide La1-xSrx(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 family. We find that
manipulation of the A-site charge state can be used to balance magnetic phase
compositions and coupling responses. This allows for the creation of highly
tunable exchange bias responses. In the low Sr doping regime, a spin frustrated
region arising at the antiferromagnetic phase boundary is shown to directly
couple to the antiferromagnetic moments of the film and emerges as the dominant
mechanism, leading to a vertical shift of magnetization loops in response to
field biasing. At higher concentrations, direct coupling of antiferromagnetic
and ferromagnetic regions is observed. This tunability of magnetic coupling is
discussed within the context of these three competing magnetic phases,
revealing critical features in designing exchange bias through exploiting spin
frustration and disorder in high entropy oxides
Phenoloxidase activity acts as a mosquito innate immune response against infection with semliki forest virus
Several components of the mosquito immune system including the RNA interference (RNAi), JAK/STAT, Toll and IMD pathways have previously been implicated in controlling arbovirus infections. In contrast, the role of the phenoloxidase (PO) cascade in mosquito antiviral immunity is unknown. Here we show that conditioned medium from the Aedes albopictus-derived U4.4 cell line contains a functional PO cascade, which is activated by the bacterium Escherichia coli and the arbovirus Semliki Forest virus (SFV) (Togaviridae; Alphavirus). Production of recombinant SFV expressing the PO cascade inhibitor Egf1.0 blocked PO activity in U4.4 cell- conditioned medium, which resulted in enhanced spread of SFV. Infection of adult female Aedes aegypti by feeding mosquitoes a bloodmeal containing Egf1.0-expressing SFV increased virus replication and mosquito mortality. Collectively, these results suggest the PO cascade of mosquitoes plays an important role in immune defence against arboviruses
Ultrafast Hole Trapping and Relaxation Dynamics in p-Type CuS Nanodisks
CuS nanocrystals are potential materials for developing low-cost solar energy conversion devices. Understanding the underlying dynamics of photoinduced carriers in CuS nanocrystals is essential to improve their performance in these devices. In this work, we investigated the photoinduced hole dynamics in CuS nanodisks (NDs) using the combination of transient optical (OTA) and X-ray (XTA) absorption spectroscopy. OTA results show that the broad transient absorption in the visible region is attributed to the photoinduced hot and trapped holes. The hole trapping process occurs on a subpicosecond time scale, followed by carrier recombination (~100 ps). The nature of the hole trapping sites, revealed by XTA, is characteristic of S or organic ligands on the surface of CuS NDs. These results not only suggest the possibility to control the hole dynamics by tuning the surface chemistry of CuS but also represent the first time observation of hole dynamics in semiconductor nanocrystals using XTA
Modeling recursive RNA interference.
An important application of the RNA interference (RNAi) pathway is its use as a small RNA-based regulatory system commonly exploited to suppress expression of target genes to test their function in vivo. In several published experiments, RNAi has been used to inactivate components of the RNAi pathway itself, a procedure termed recursive RNAi in this report. The theoretical basis of recursive RNAi is unclear since the procedure could potentially be self-defeating, and in practice the effectiveness of recursive RNAi in published experiments is highly variable. A mathematical model for recursive RNAi was developed and used to investigate the range of conditions under which the procedure should be effective. The model predicts that the effectiveness of recursive RNAi is strongly dependent on the efficacy of RNAi at knocking down target gene expression. This efficacy is known to vary highly between different cell types, and comparison of the model predictions to published experimental data suggests that variation in RNAi efficacy may be the main cause of discrepancies between published recursive RNAi experiments in different organisms. The model suggests potential ways to optimize the effectiveness of recursive RNAi both for screening of RNAi components as well as for improved temporal control of gene expression in switch off-switch on experiments
Study of and
The decays and have been
investigated with a sample of 225.2 million events collected with the
BESIII detector at the BEPCII collider. The branching fractions are
determined to be and . Distributions of the angle
between the proton or anti-neutron and the beam direction are well
described by the form , and we find
for and
for . Our branching-fraction
results suggest a large phase angle between the strong and electromagnetic
amplitudes describing the decay.Comment: 16 pages, 13 figures, the 2nd version, submitted to PR
The inflammatory microenvironment in colorectal neoplasia
Peer reviewedPublisher PD
Detection of a Cosmic Ray with Measured Energy Well Beyond the Expected Spectral Cutoff due to Cosmic Microwave Radiation
We report the detection of a 51-joule (320 +/- 90 EeV) cosmic ray by the
Fly's Eye air shower detector in Utah. This is substantially greater than the
energy of any previously reported cosmic ray. A Greisen-Zatsepin-Kuz'min cutoff
of the energy spectrum (due to pion photoproduction energy losses) should occur
below this energy unless the highest energy cosmic rays have traveled less than
about 30 Mpc. The error box for the arrival direction in galactic coordinates
is centered on b=9.6 deg, l=163.4 deg. The particle cascade reached a maximum
size near a depth of 815 g/cm^2 in the atmosphere, a depth which does not
uniquely identify the type of primary particle.Comment: uuencoded compressed postscript, 20 pages, to appear in ApJ (3/1/95
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