Thin flexible sheets of high-permeability FINEMET® foils encased in thin plastic layers have been used to shield various types of 20-cm-diameter photomultiplier tubes from ambient magnetic fields. In ...the presence of the Earth's magnetic field this type of shielding is shown to increase the collection efficiency of photoelectrons and can improve the uniformity of response of these photomultiplier tubes.
With the increasingly common use of large area PMTs (photomultiplier tubes) for nuclear and particle physics experiments, information on the position dependent magnetic field effects across the PMT's ...photocathode is important to effectively analyze and understand data collected from PMTs. Using an automated two-dimensional scanner, we have measured the PMT response to an external magnetic field as a function of the cathode position impinged by a collimated light source. This study shows a clear dependence on the cathode position in both collection efficiency and gain of the PMT in the presence of a magnetic field. In particular, a pronounced valley in the collection efficiency is observed for certain locations of the cathode when the magnetic field is transverse to the PMT axis. The pattern of the position dependence is presented for several different magnitudes and orientations of the magnetic field relative to the PMT.
Recent results in d+Au and p+Pb collisions at RHIC and the LHC provide evidence for collective expansion and flow of the created medium. We propose a control set of experiments to directly compare ...particle emission patterns from p+Au, d+Au, and He3+Au or t+Au collisions at the same sqrt(sNN). Using Monte Carlo Glauber we find that a He3 or triton projectile, with a realistic wavefunction description, induces a significant intrinsic triangular shape to the initial medium and that, even with viscous damping, this survives into a significant third order flow moment v3. By comparing systems with one, two, and three initial hot spots, one can disentangle the effects from the initial spatial distribution of the deposited energy and viscous damping. These are key tools to answering the question of how small a droplet of matter is necessary to form a quark-gluon plasma described by nearly inviscid hydrodynamics.
With the increasingly common use of large area PMTs (photomultiplier tubes) for nuclear and particle physics experiments, information on the position dependent magnetic field effects across the PMT's ...photocathode is important to effectively analyze and understand data collected from PMTs. Using an automated two-dimensional scanner, we have measured the PMT response to an external magnetic field as a function of the cathode position impinged by a collimated light source. This study shows a clear dependence on the cathode position in both collection efficiency and gain of the PMT in the presence of a magnetic field. In particular, a pronounced valley in the collection efficiency is observed for certain locations of the cathode when the magnetic field is transverse to the PMT axis. The pattern of the position dependence is presented for several different magnitudes and orientations of the magnetic field relative to the PMT.
Thin flexible sheets of high-permeability FINEMET foils encased in thin plastic layers have been used to shield various types of 20-cm-diameter photomultiplier tubes from ambient magnetic fields. In ...the presence of the Earth's magnetic field this type of shielding is shown to increase the collection efficiency of photoelectrons and can improve the uniformity of response of these photomultiplier tubes.
Animal Behavior: Honesty Can Kill Koblesky, Norah; Stowers, Lisa
CB/Current biology,
04/2019, Letnik:
29, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Virgin male mice naturally kill another male’s pups so they can sire their own offspring. New research shows that pups are identified using a combination of generic and ‘honest’ cues, revealing an ...unexpected logic underlying pup recognition and ensuing infanticide.
Virgin male mice naturally kill another male’s pups so they can sire their own offspring. New research shows that pups are identified using a combination of generic and ‘honest’ cues, revealing an unexpected logic underlying pup recognition and ensuing infanticide.
The 22 γ-Protocadherin (γ-Pcdh) cell adhesion molecules are critical for the elaboration of complex dendritic arbors in the cerebral cortex. Here, we provide evidence that the γ-Pcdhs negatively ...regulate synapse development by inhibiting the postsynaptic cell adhesion molecule, neuroligin-1 (Nlg1). Mice lacking all γ-Pcdhs in the forebrain exhibit significantly increased dendritic spine density in vivo, while spine density is significantly decreased in mice overexpressing one of the 22 γ-Pcdh isoforms. Co-expression of γ-Pcdhs inhibits the ability of Nlg1 to increase spine density and to induce presynaptic differentiation in hippocampal neurons in vitro. The γ-Pcdhs physically interact in cis with Nlg1 both in vitro and in vivo, and we present evidence that this disrupts Nlg1 binding to its presynaptic partner neurexin1β. Together with prior work, these data identify a mechanism through which γ-Pcdhs could coordinate dendrite arbor growth and complexity with spine maturation in the developing brain.
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•γ-Protocadherins (γ-Pcdhs) regulate dendritic spine morphogenesis in the cerebral cortex•γ-Pcdhs interact with neuroligin-1 (Nlg1) and inhibit its interaction with neurexin1β•γ-Pcdhs inhibit Nlg1’s ability to induce presynaptic differentiation in vitro•γ-Pcdhs inhibit Nlg1’s ability to increase dendritic spine density in vitro
Using conditional mutant and overexpression mouse lines, Molumby et al. demonstrate that γ-Protocadherins negatively regulate cortical dendritic spine morphogenesis in vivo. The γ-Protocadherins interact physically with neuroligin-1 and inhibit its ability to bind neurexin1β, to promote presynaptic differentiation, and to increase dendritic spine density in hippocampal neurons in vitro.
Cognitive decline in aging is marked by considerable variability, with some individuals experiencing significant impairments and others retaining intact functioning. Whereas previous studies have ...linked elevated hypothalamo-pituitary-adrenal (HPA) axis activity with impaired hippocampal function during aging, the idea has languished regarding whether such differences may underlie the deterioration of other cognitive functions. Here we investigate whether endogenous differences in HPA activity are predictive of age-related impairments in prefrontal structural and behavioral plasticity. Young and aged rats (4 and 21 months, respectively) were partitioned into low or high HPA activity, based upon averaged values of corticosterone release from each animal obtained from repeated sampling across a 24 h period. Pyramidal neurons in the prelimbic area of medial prefrontal cortex were selected for intracellular dye filling, followed by 3D imaging and analysis of dendritic spine morphometry. Aged animals displayed dendritic spine loss and altered geometric characteristics; however, these decrements were largely accounted for by the subgroup bearing elevated corticosterone. Moreover, high adrenocortical activity in aging was associated with downward shifts in frequency distributions for spine head diameter and length, whereas aged animals with low corticosterone showed an upward shift in these indices. Follow-up behavioral experiments revealed that age-related spatial working memory deficits were exacerbated by increased HPA activity. By contrast, variations in HPA activity in young animals failed to impact structural or behavioral plasticity. These data implicate the cumulative exposure to glucocorticoids as a central underlying process in age-related prefrontal impairment and define synaptic features accounting for different trajectories in age-related cognitive function.
One’s perception of the world is personal. Different people can experience the same sensory stimulus in myriad ways, and the same person can experience the same sensory stimulus differently across ...time. What factors cause sensory experiences to differ? While daunting, identifying the sources of individualized perception is essential to understanding how the brain functions—to truly understand a circuit, one must understand how inputs are processed. Olfaction, which is essential for many complex mouse behaviors and influenced by both experience and state, is a prime candidate for the study of such variation. While olfactory variation is known to exist, the biological, historical, or technical factors it stems from are not. Here, we find two sources of olfactory variation, one biological and one technical. In the first chapter, we find that pheromone-evoked activity is mediated not by one signal transduction cascade but several. None of the discovered signal transduction cascades are dominant, indicating that signaling heterogeneity is an integral feature in the vomeronasal system. These signal transduction cascades are stimulus-specific, hinting at a substantial utility. The discovery of multiple signaling pathways in the vomeronasal system identifies a new source for biological variation in olfaction. In the second chapter of this thesis, we find that the assay and apparatus used for innate olfactory valence tests affect results’ strengths, timing, and conclusions, indicating that current unstandardized assays introduce substantial technical variation to data. We also show that raw data from these assays are unimpressive, often requiring transformation to become significant. Analysis of tests’ raw data reveals that mice are initially attracted to all stimuli and aversive reactions take minutes to manifest—these data suggest that the currently-used position-as-reaction measure is flawed and needs to be replaced. Uncovering these sources of biological and technical variation poises the neuroscience community to understand how animals make sense of the world around them.
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