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Purpose Mice are often used as small animal models of brain ischemia, venous thrombosis, or vasospasm. This article aimed at providing an overview of the currently available methodologies for in vivo imaging of the murine cerebrovasculature and comparing the capabilities and limitations of the different methods. Methods Micro-computed tomography angiography (CTA) was performed during intra-arterial and intravenous administration of a contrast agent bolus. Digital subtraction angiography (DSA) was performed during intra-arterial administration of contrast agent using the micro-CT scanner. Time-of-flight (ToF) magnetic resonance (MR) angiography was performed using a small animal scanner (9.4 T) equipped with a cryogenic transceive quadrature coil. Datasets were compared for scan time, contrast-to-noise ratio (CNR), temporal and spatial resolution, radiation dose, contrast agent dose and detailed recognition of cerebrovascular structures. Results Highest spatial resolution was achieved using micro-CTA (16 ´ 16 ´ 16 µm) and DSA (14 ´ 14 µm). Compared to micro-CTA (20–40 s) and ToF-MRA (57 min), DSA provided highest temporal resolutions (30 fps) allowing analyses of the cerebrovascular blood flow. Highest mean CNR was reached using ToF-MRA (50.7 ± 15.0), while CNR of micro-CTA depended on the intra-arterial (19.0 ± 1.0) and intravenous (1.3 ± 0.4) use of agents. The CNR of DSA was 10.0 ± 1.8. Conclusions The use of dedicated small animal scanners allows cerebrovascular imaging in live animals as small as mice. As each of the methods analyzed has its advantages and limitations, choosing the best suited imaging modality for a defined question is of great importance. By this means the aforementioned methods offer a great potential for future projects in preclinical cerebrovascular research including ischemic stroke or vasospasm.

The interaction between antiprotons, produced by colliding high-energy gold ions, is shown to be attractive, and two important parameters of this interaction are measured, namely the scattering length and the effective range. Antiproton pair correlations strike gold The forces acting between between atomic nuclei are experimentally known to great precision, but those between antinuclei have proven difficult to measure. Antinuclei have been detected before, but it is a considerable technical challenge to produce them in sufficient quantities to measure interaction between them. Here the STAR Collaboration, working with the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, has succeeded in measuring antiproton interaction. The antiprotons are produced by colliding high-energy gold atoms. The authors show that antiproton interaction is attractive and measure two important parameters that are characteristic of this interaction — the scattering length and the effective range. The results quantitatively verify matter–antimatter symmetry and open opportunities for further precision tests. One of the primary goals of nuclear physics is to understand the force between nucleons, which is a necessary step for understanding the structure of nuclei and how nuclei interact with each other. Rutherford discovered the atomic nucleus in 1911, and the large body of knowledge about the nuclear force that has since been acquired was derived from studies made on nucleons or nuclei. Although antinuclei up to antihelium-4 have been discovered 1 and their masses measured, little is known directly about the nuclear force between antinucleons. Here, we study antiproton pair correlations among data collected by the STAR experiment 2 at the Relativistic Heavy Ion Collider (RHIC) 3 , where gold ions are collided with a centre-of-mass energy of 200 gigaelectronvolts per nucleon pair. Antiprotons are abundantly produced in such collisions, thus making it feasible to study details of the antiproton–antiproton interaction. By applying a technique similar to Hanbury Brown and Twiss intensity interferometry 4 , we show that the force between two antiprotons is attractive. In addition, we report two key parameters that characterize the corresponding strong interaction: the scattering length and the effective range of the interaction. Our measured parameters are consistent within errors with the corresponding values for proton–proton interactions. Our results provide direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, and so are fundamental to understanding the structure of more-complex antinuclei and their properties.

A large-area Time-of-Flight (TOF) system based on Multi-gap Resistive Plate Chambers (MRPCs) has recently been installed in the STAR experiment at RHIC. The approximately 23000 detector channels are read out and digitized using custom electronics based on the CERN NINO and HPTDC chips. The data are sent to the experimental data acquisition system (DAQ) using the ALICE fiber optics based Detector Data Link (DDL). The readout system consists of a total of approximately 2100 custom electronics boards mounted directly on 120 TOF trays, as well as four DAQ and trigger interface boards outside the detector that collect data from 30 trays each and send it to DAQ. Control and monitoring of these electronics boards is done using a tiered network of CANbus connections to a control PC. We describe the physical implementation and topology of the CANbus connections and the custom protocol developed for this project. Several command-line tools as well as a Qt4-based graphical tool developed on the host side to facilitate configuration, control, and monitoring of the TOF system are also described.

Stem cells support tissue maintenance by balancing self-renewal and differentiation. In mice, it is believed that a homogeneous stem cell population of single spermatogonia supports spermatogenesis, and that differentiation, which is accompanied by the formation of connected cells (cysts) of increasing length, is linear and nonreversible. We evaluated this model with the use of lineage analysis and live imaging, and found that this putative stem cell population is not homogeneous. Instead, the stem cell pool that supports steady-state spermatogenesis is contained within a subpopulation of single spermatogonia. We also found that cysts are not committed to differentiation and appear to recover stem cell potential by fragmentation, and that the fate of individual spermatogonial populations was markedly altered during regeneration after damage. Thus, there are multiple and reversible paths from stem cells to differentiation, and these may also occur in other systems.

Ultrarelativistic heavy-ion collisions produce a state of hot and dense strongly interacting QCD matter called quark-gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultracentral collisions is mostly constant, while its total entropy can vary significantly due to quantum fluctuations, leading to variations in the temperature of the system. Exploiting this unique feature of ultracentral collisions allows for the interpretation of the correlation of the mean transverse momentum (〈pT〉) of produced charged hadrons and the number of charged hadrons as a measure for the speed of sound, cs. This speed is related to the rate at which compression waves travel in the QGP and is determined by fitting the relative increase in 〈pT〉 with respect to the relative change in the average charged-particle density (〈dNch/dη〉) measured at mid-rapidity. This study reports the event-average 〈pT〉 of charged particles as well as the variance, skewness, and kurtosis of the event-by-event transverse momentum per charged particle ([pT]) distribution in ultracentral Pb-Pb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are used to select ultracentral collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region used to perform the measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum is tested. The measured c²_(s) is found to strongly depend on the exploited centrality estimator and ranges between 0.1146±0.0028 (stat.)±0.0065 (syst.) and 0.4374±0.0006 (stat.)±0.0184 (syst.) in natural units. The self-normalized variance shows a steep decrease towards ultracentral collisions, while the self-normalized skewness variables show a maximum, followed by a fast decrease. These non-Gaussian features are understood in terms of the vanishing of the impact-parameter fluctuations contributing to the event-to-event [pT] distribution.

The transverse momentum spectra and integrated yields of anti-$$\\Sigma $$Σ hyperons ($$\\overline{\\Sigma }^{\\pm } $$Σ ¯ ± ) have been measured in$$\\text {pp}$$pp and$$\\text {p}{-}\\text {Pb}$$p - Pb collisions at$$\\sqrt{s_{\\textrm{NN}}}=5.02$$s NN = 5.02 TeV with the ALICE experiment. Measurements are performed via the newly accessed decay channel$$\\overline{\\Sigma }^{\\pm } \\!\\!\\rightarrow \\mathrm{\\overline{n}} \\pi ^{\\pm }$$Σ ¯ ± → n ¯ π ± . A new method of antineutron reconstruction with the PHOS electromagnetic spectrometer is developed and applied to this analysis. The$$p_{\\textrm{T}}$$p T spectra of$$\\overline{\\Sigma }^{\\pm } $$Σ ¯ ± are measured in the range$$0.5

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