The Interplay of Interstitial and Substitutional Copper in Zinc Oxide

Cu impurities are reported to have significant effects on the electrical and optical properties of bulk ZnO. In this work, we study the defect properties of Cu in ZnO using hybrid quantum mechanical/molecular mechanical (QM/MM)–embedded cluster calculations based on a multi-region approach that allows us to model defects at the true dilute limit, with polarization effects described in an accurate and consistent manner. We compute the electronic structure, energetics, and geometries of Cu impurities, including substitutional and interstitial configurations, and analyze their effects on the electronic structure. Under ambient conditions, CuZn is the dominant defect in the d9 state and remains electronically passive. We find that, however, as we approach typical vacuum conditions, the interstitial Cu defect becomes significant and can act as an electron trap.

Optimizing a left and right visual field biphasic stimulation paradigm for SSVEP-based BCIs with hairless region behind the ear

Objective. Steady-state visual evoked potential (SSVEP) based brain-computer interface (BCI) has the characteristics of fast communication speed, high stability, and wide applicability, thus it has been widely studied. With the rapid development in paradigm, algorithm, and system design, SSVEP-BCI is gradually applied in clinical and real-life scenarios. In order to improve the ease of use of the SSVEP-BCI system, many studies have been focusing on developing it on the hairless area, but due to the lack of redesigning the stimulation paradigm to better adapt to the new area, the EEG response in the hairless area is worse than occipital region. Approach. This study first proposed a phase difference estimation method based on stimulating the left and right visual field separately, then developed and optimized a left and right visual field biphasic stimulation paradigm for SSVEP-based BCIs with hairless region behind the ear. Main results. In the 12-target online experiment, after a short model estimation training, all sixteen subjects used their best stimulus condition. The paradigm designed in this study can increase the proportion of applicable subjects for the behind-ear SSVEP-BCI system from 58.3% to 75% and increase the accuracy from 74.6±20.0% (the existing best SSVEP stimulus with hairless region behind the ear) to 84.2±14.7%, and the ITR from 14.2±6.4bits/min to 17.8±5.7bits/min. Significance. These results demonstrated that the proposed paradigm can effectively improve the BCI performance using the signal from the hairless region behind the ear, compared with the standard SSVEP stimulation paradigm.

Differential Effects of Exercise on fMRI of the Midbrain Ascending Arousal Network Nuclei in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) and Gulf War Illness (GWI) in a Model of Postexertional Malaise (PEM)

Background: Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS), Gulf War Ill-ness (GWI) and control subjects had fMRI during difficult cognitive tests performed before and after submaximal exercise provocation (Washington 2020). Exercise caused increased activation in ME/CFS but decreased activation for GWI in the dorsal midbrain, left Rolandic operculum and right middle insula. Midbrain and isthmus nuclei participate in threat assessment, attention, cognition, mood, pain, sleep, and autonomic dysfunction Methods: Activated midbrain nuclei were inferred by re-analysis of data from 31 control, 36 ME/CFS and 78 GWI subjects using a seed region approach and the Harvard Ascending Arousal Network. Results: Before exercise, control and GWI had greater activation during cognition than ME/CFS in left pedunculotegmental nucleus. Postexercise ME/CFS had greater activation than GWI for midline periaqueductal gray, dorsal and median raphe, and right midbrain reticular formation, parabrachial complex and locus coeruleus. The change between days (delta) was positive for ME/CFS but negative for GWI indicating reciprocal patterns of activation. Controls had no changes. Conclusions: Exercise caused opposite effects with increased activation in ME/CFS but decreased activation in GWI indicating different pathophysiological responses to exertion and mechanisms of disease. Midbrain and isthmus nuclei contribute to postexertional malaise in ME/CFS and GWI.

Gasification of Waste Tyres: Thermodynamic Attainable Region Approach

The innovative G-H graphical technique, a plot of Enthalpy vs Gibbs free energy was utilized to obtain a thermodynamically attainable region (AR) for the gasification of waste tyres. The AR is used to examine the interaction between the competing reactions in a gasifier and used to identify optimal targets for the conversion of waste tyres. The objective is to investigate the effect of temperature on the product selectivity. a temperature range of 25-1500°C at 1 bar was used for the analysis. The results show that at temperatures from 200°C to 600°C methane and carbon dioxide are dominant products at minimum Gibbs free energy. However, as the temperature increases, methane production decreases and hydrogen production become more favourable. Between 600°C and 700°C, carbon dioxide and hydrogen are dominant products. The AR results show that the products of gasification (CO and H2) are preferred products at minimum Gibbs free energy only at temperatures from 800°C to 1500°C, when both water and oxygen are used as oxidants. Therefore, syngas production from tyres is only feasible at high temperatures. Temperatures above 1000°C are recommended to prevent the formation of intermediate radicals.

Trapped Gravitational Waves in Jackiw–Teitelboim Gravity

We discuss the possibility that gravitational fluctuations (“gravitational-waves”) are trapped in space by gravitational interactions in two dimensional Jackiw–Teitelboim gravity. In the standard geon (gravitational electromagnetic entity) approach, the effective energy is entirely deposited in a thin layer, the active region, that achieves spatial self-confinement and raises doubts about the geon’s stability. In this paper we relinquish the “active region” approach and obtain self-confinement of “gravitational waves” that are trapped by the vacuum geometry and can be stable against the backreaction due to metric fluctuations.

الشيخ مختار بن عطارد البوغوري الجاوي ثم المكي (1862 – 1930) والكتب الصونداوية المطبوعة في مكة والقاهرة أوائل القرن العشرين

This paper examines the history of “Kitab Sunda”, which was written in Sundanese language but with Arabic letter, by Shaikh Mukhtar (1862 – 1930) in Mecca and printed in Cairo and Mecca. While most intellectual works in the Middle East were written in Arabic, there is convincing indication that they were written in non-Arabic language. It is surprising fact that many religious-based works (Islam) were written in Arabic letter, but they used Javanese, Malay and Sundanese. One of important agents of Muslim scholar who purposely used Sundanese language in his work is Shaikh Mukhtar. The writer, born in Bogor (West Java), was a great ulama (Muslim scholar) in Mecca. He was connected with ulama from nusantara and Middle East network in the turn of 19 and 20 century. During the important period, there were some ulama from Sunda who were teaching in Mecca. Some of them wrote books printed in several cities in the Middle East such as Mecca, Cairo and Istanbul. Shaikh Mukhtar is well-known as pioneer of authorship and publicity of Kitab Sunda in Middle East since the early 20th century. Before this period, religious works of ulama nusantara written in nusantara language and printed in the Middle East, only written in Malay language and Javanese. In the Middle East, history of authorship of kitab Sunda was initiated by Shaikh Mukhtar. This achievement is important not only to introduce Sundanese language as the intelectual language in the Middle East through his works, but also inspire his disciple to produce intellectual works in their mother tongue. By means of historical and bibliography of region approach, this study traces the role of Suandanese ulama in Middle East in the early 20th century.