Resting-state Arterial Spin Labeling (rs-ASL) is a rather confidential method compared to resting-state BOLD. As ASL allows to quantify the cerebral blood flow, unlike BOLD, rs-ASL can lead to ...significant clinical subject-scaled applications. Despite directly impacting clinical practicability and functional networks estimation, there is no standard for rs-ASL regarding the acquisition duration. Our work here focuses on assessing the feasibility of ASL as an rs-fMRI method and on studying the effect of the acquisition duration on the estimation of functional networks. To this end, we acquired a long 24 min 30 s rs-ASL sequence and investigated how estimations of six typical functional brain networks evolved with respect to the acquisition duration. Our results show that, after a certain acquisition duration, the estimations of all functional networks reach their best and are stabilized. Since, for clinical application, the acquisition duration should be the shortest possible, we suggest an acquisition duration of 14 min, i.e., 240 volumes with our sequence parameters, as it covers the functional networks estimation stabilization.
Puberty is a time of intense reorganization of brain structure and a high-risk period for the onset of mental health problems, with variations in pubertal timing and tempo intensifying this risk. We ...conducted two systematic reviews of papers published up to 1st February 2024 focusing on (1) the role of brain structure in the relationship between puberty and mental health, and (2) precision psychiatry research evaluating the utility of puberty in making individualized predictions of mental health in young people. The first review provides inconsistent evidence on whether and how pubertal and psychopathological processes could interact in relation to brain development. While most studies found an association between early puberty and mental health difficulties in adolescents, evidence on whether brain structure mediates this relationship is mixed. The pituitary gland was found to be associated with mental health status during this time, possibly through its central role in regulating puberty and its function in the hypothalamic- pituitary-gonadal (HPG) and hypothalamic-pituitary-adrenal (HPA) axes. In the second review, the design of studies that have explored puberty in predictive models did not allow for a quantification of its predictive power. However, when puberty was evaluated through physically observable characteristics rather than hormonal measures, it was more commonly identified as a predictor of depression, anxiety, and suicidality in adolescence. Social processes might be more relevant than biological ones in the link between puberty and mental health problems, and represent an important target for educational strategies.
Plasma enhanced atomic layer deposition (PE-ALD) of aluminum nitride (AlN) thin films often utilizes NH3 or a mixture of N2 and H2 as a plasma source. However, the possibility of separating the ...activation step from the nitridation step by using H2 alone as the plasma source has never been explored. In this paper, we study the deposition of AlN by PE-ALD by using trimethylaluminum, H2 plasma and NH3 for deposition temperatures below 400 °C. The self-limiting ALD growth was achieved between 325 °C and 350 °C. As a comparison, AlN was also deposited by thermal ALD (T-ALD), where surface reactions between TMA and NH3 occurred with reasonable growth rates only at temperatures above 400 °C. The PE-ALD films showed low oxygen (1.5 at.%) and carbon contaminations (1 at.%). The T-ALD films contained carbon (5 at.%) mainly attributed to the presence of CAl bonds that was insignificant in PE-ALD films. The flow rate of H2 used in H2 plasma was found to have a significant impact on the preferred orientation of AlN films, where higher H2 flow rate promoted the (002) preferred orientation. Besides, the electrical resistivities were probed to be 108 Ω cm, as expected in an insulating material.
As an example, AlN was used to infiltrate porous sintered silicon carbide (SiC). Both AlN deposited by PE-ALD and by T-ALD operating with exposure mode deposited at 400 °C were attempted. Even though, there is a greater risk for TMA precursor to decompose at 400 °C, infiltration of AlN was more successful by T-ALD operating with exposure mode.
•A new approach to deposit AlN by plasma enhanced atomic layer deposition was developed.•The flow rate of H2 used in H2 plasma was found to have a significant impact on the preferred orientation of AlN films.•Infiltrations of porous sintered SiC by AlN deposited by plasma enhanced atomic layer deposition was demonstrated.
We present a multidomain spectral approach for Fuchsian ordinary differential equations in the particular case of the hypergeometric equation. Our hybrid approach uses Frobenius’ method and Moebius ...transformations in the vicinity of each of the singular points of the hypergeometric equation, which leads to a natural decomposition of the real axis into domains. In each domain, solutions to the hypergeometric equation are constructed via the well-conditioned ultraspherical spectral method. The solutions are matched at the domain boundaries to lead to a solution which is analytic on the whole compactified real line
ℝ
∪
∞
, except for the singular points and cuts of the Riemann surface on which the solution is defined. The solution is further extended to the whole Riemann sphere by using the same approach for ellipses enclosing the singularities. The hypergeometric equation is solved on the ellipses with the boundary data from the real axis. This solution is continued as a harmonic function to the interior of the disk by solving the Laplace equation in polar coordinates with an optimal complexity Fourier–ultraspherical spectral method. In cases where logarithms appear in the solution, a hybrid approach involving an analytical treatment of the logarithmic terms is applied. We show for several examples that machine precision can be reached for a wide class of parameters, but also discuss almost degenerate cases where this is not possible.
In this study, the dielectric properties of metal-oxide-metal capacitors based on Tantalum Titanium Oxide (TiTaO) thin films deposited by reactive magnetron sputtering on aluminum bottom electrode ...are investigated. The structure of the films was characterized by Atomic Force Microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric properties of TiTaO thin films were studied by complex impedance spectroscopy over a wide frequency range (10-2 - to 105Hz) and temperatures in -50°C to 325°C range. The contributions of different phases, phases’ boundaries and conductivity effect were highlighted by Cole – Cole diagram (ɛ” versus ɛ’). Two relaxation processes have been identified in the electric modulus plot. A first relaxation process appears at low temperature with activation energy of 0.37eV and it is related to the motion of Ti4+ (Skanavi’s model). A second relaxation process at high temperature is related to Maxwell-Wagner-Sillars relaxation with activation energy of 0.41eV.
•Titanium Tantalum Oxide thin films are grown on Aluminum substrate.•The existence of phases was confirmed by X-ray photoelectron spectroscopy.•Conductivity effect appears in Cole-Cole plot.•At low temperatures, a relaxation phenomenon obeys to Skanavi’s model.•Maxwell-Wagner-Sillars polarization is processed at high temperatures.
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