Multimodality magnetic resonance imaging in hepatic encephalopathy: An update

Hepatic encephalopathy(HE) is a neuropsychiatric complication of cirrhosis or acute liver failure. Currently, HE is regarded as a continuous cognitive impairment ranging from the mildest stage, minimal HE to overt HE. Hyperammonaemia and neuroinflammation are two main underlying factors which contribute to the neurological alterations in HE. Both structural and functional impairments are found in the white mater and grey mater involved in HE. Although the investigations into HE pathophysiological mechanism are enormous, the exact pathophysiological causes underlying HE remain controversial. Multimodality magnetic resonance imaging(MRI) plays an important role in helping to understand the pathological process of HE. This paper reviews the up-to-date multimodality MRI methods and predominant findings in HE patients with a highlight ofthe increasingly important role of blood oxygen level dependent functional MRI.

BOLD-fMRI study of auditory cortex in patients with tinnitus

Objective Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) was used to study activation signals in the brain cortex evoked by tone stimulation in patients with tinnitus for its potential utility as an objective indicator of tinnitus. Methods BOLD-fMRI examination was conducted in 7 patients with chronic tinnitus and 15 control subjects. The activation signal in the brain cortex was recorded. Results Significant activation was found in temporal lobe in control subjects, with greater signal volume and intensity on the contralateral than ipsilateral auditory cortex (P < 0.01). However, there was no discernable patterns in the anatomical location, volume and intensity of cortical activation signals in patients with chronic tinnitus. Conclusions Patients with chronic tinnitus may have abnormal neural activities in the auditory cortex.

A simple Pb-doping to achieve bonding evolution, VSn and resonant level shifting for regulating thermoelectric transport behavior of SnTe

The intensification of energy crises and environmental pollution inspire researchers’attention to environment-friendly SnTe thermoelectric materials.In this work,we achieved a lower lattice thermal conductivity and optimized the power factor via the synergistic optimization of bonding characteristic,VSn,and resonant level for the SnTe system,respectively.Pb-introduction produces weak bonding strength,mass fluctuation,and stress distortion,which result in lower thermal conductivity.The lowest lattice thermal conductivity achieves 0.66 W m^(–1) K^(–1) at 773 K.Further introduced VSn relieves loss of electrical conductivity caused by Pb-introduction,and it also makes the bigger g(E)and up-shift of resonance level.The VSn,enhanced g(E),and resonant level make electrical conductivity and Seebeck coefficient enhance simultaneously.Finally,the further optimization of thermal and electronic transport performance contributes to a higher ZT value of∼0.86 at 773 K in the Sn_(0.685)Pb_(0.285)In_(0.015)Te_(0.7)Se_(0.3) sample.The strategy of bonding characteristic,VSn,and resonant level synergistic engineering will be widely applicable to various TE systems for achieving better thermoelectric performance.

Exploration of resonances by using complex momentum representation

Resonance research is a hot topic in nuclear physics,and many methods have been developed for resonances.In this paper,we explore resonances by solving the Schrodinger equation in complex momentum representation,in which the bound states and resonant states are separated completely from the continuum and exposed clearly in the complex momentum plane.We have checked the convergence of the calculations on the grid numbers of the Gauss-Hermite quadrature and the Gauss-Legendre quadrature,and the dependence on the contour of momentum integration.Satisfactory results are obtained.^17O is chosen as an example,and we have calculated the bound and resonant states to be in excellent agreement with those calculated in the coordinate representation.

Band modification towards high thermoelectric performance of SnSb_(2)Te_(4) with strong anharmonicity driven by cation disorder

As a typical (IV–VI)_(x)(V_(2)VI_(3))_(y) compound, the tetradymite-like layered SnSb_(2)Te_(4) -based compounds have attracted increasing attention in the thermoelectric community owing to the intrinsically low lattice thermal conductivity. Nevertheless, the effect of cations disorder on the inherent physical characteristics remains puzzling, and its inferior Seebeck coefficient is the bottleneck to achieving high thermoelectric performance. In this work, the thermoelectric properties of polycrystalline In_(x)Sn_(1−x)Sb_(2)(Te_(1−y)Se_(y))_(4) (0≤x≤0.1,0≤y≤0.15) samples are comprehensively investigated. In conjunction with the calculated band structure and experimental results, the Seebeck coefficient and power factor are markedly improved after the introduction of indium and selenium, which originates from the combined effects of the emergent resonant states and converged valence bands along with optimal carrier concentration. Additionally, compared with the ordered lattice structure, the disordered cations occupancy in SnSb_(2)Te_(4) further strengthens lattice anharmonicity and reduces phonon group velocity verified by first-principles calculations, securing intrinsically low lattice thermal conductivity. Finally, a record zT value of ∼0.6 at 670 K and an average zT of ∼0.4 between 320 and 720 K are obtained in the In0.1 Sn0.9 Sb2 Te3.4 Se0.6 sample, being one of the highest zT values among SnSb2 Te4 -based materials. This work not only demonstrates that SnSb2 Te4 -based compounds are promising thermoelectric candidates, but also provides guidance for the promotion of thermoelectric performance in a broad temperature range.