Amplitude modulating frequency overrides carrier frequency in tACS-induced phosphene percept.

The amplitude modulated (AM) neural oscillation is an essential feature of neural dynamics to coordinate distant brain areas. The AM transcranial alternating current stimulation (tACS) has recently been adopted to examine various cognitive functions, but its neural mechanism remains unclear. The current study utilized the phosphene phenomenon to investigate whether, in an AM-tACS, the AM frequency could modulate or even override the carrier frequency in phosphene percept. We measured the phosphene threshold and the perceived flash rate/pattern from 12 human subjects (four females, aged from 20-44 years old) under tACS that paired carrier waves (10, 14, 18, 22 Hz) with different envelope conditions (0, 2, 4 Hz) over the mid-occipital and left facial areas. We also examined the phosphene source by adopting a high-density stimulation montage. Our results revealed that (1) phosphene threshold was higher for AM-tACS than sinusoidal tACS and demonstrated different carrier frequency functions in two stimulation montages. (2) AM-tACS slowed down the phosphene flashing and abolished the relation between the carrier frequency and flash percept in sinusoidal tACS. This effect was independent of the intensity change of the stimulation. (3) Left facial stimulation elicited phosphene in the upper-left visual field, while occipital stimulation elicited equally distributed phosphene. (4) The near-eye electrodermal activity (EDA) measured under the threshold-level occipital tACS was greater than the lowest power sufficient to elicit retinal phosphene. Our results show that AM frequency may override the carrier frequency and determine the perceived flashing frequency of AM-tACS-induced phosphene.

Elucidating the Reaction Mechanism of Atomic Layer Deposition of Al2O3 with a Series of Al(CH3)xCl3-x and Al(CyH2y+1)3 Precursors.

The adsorption of metalorganic and metal halide precursors on the SiO2 surface plays an essential role in thin-film deposition processes such as atomic layer deposition (ALD). In the case of aluminum oxide (Al2O3) films, the growth characteristics are influenced by the precursor structure, which controls both chemical reactivity and the geometrical constraints during deposition. In this work, a systematic study using a series of Al(CH3)xCl3-x (x = 0, 1, 2, and 3) and Al(CyH2y+1)3 (y = 1, 2, and 3) precursors is carried out using a combination of experimental spectroscopic techniques together with density functional theory calculations and Monte Carlo simulations to analyze differences across precursor molecules. Results show that reactivity and steric hindrance mutually influence the ALD surface reaction. The increase in the number of chlorine ligands in the precursor shifts the deposition temperature higher, an effect attributed to more favorable binding of the intermediate species due to higher Lewis acidity, while differences between precursors in film growth per cycle are shown to originate from variations in adsorption activation barriers and size-dependent saturation coverage. Comparison between the theoretical and experimental results indicates that the Al(CyH2y+1)3 precursors are favored to undergo two ligand exchange reactions upon adsorption at the surface, whereas only a single Cl-ligand exchange reaction is energetically favorable upon adsorption by the AlCl3 precursor. By pursuing the first-principles design of ALD precursors combined with experimental analysis of thin-film growth, this work enables a robust understanding of the effect of precursor chemistry on ALD processes.

Depressive rumination is correlated with brain responses during self-related processing.

BACKGROUND: Rumination, a tendency to focus on negative self-related thoughts, is a central symptom of depression. Studying the self-related aspect of such symptoms is challenging because of the need to distinguish self effects from the emotional content of task stimuli. This study employed an emotionally neutral self-related paradigm to investigate possible altered self-processing in depression and its link to rumination. METHODS: People with major depressive disorder (n = 25) and controls (n = 25) underwent task-based electro-encephalogram recording. We studied late event-related potentials, along with low-frequency oscillatory power. We compared electroencephalogram metrics between groups and correlated them with depressive symptoms and reported rumination. RESULTS: Participants with major depressive disorder displayed a difference in late positive potentials across frontocentral electrodes between self-related and non-self-related conditions. We found no such difference in controls. The magnitude of this difference was positively correlated with depressive symptoms and reported rumination. Participants with major depressive disorder also had elevated theta oscillation power at central electrodes in self-related conditions, a finding that we did not see in controls. LIMITATIONS: Patients with major depressive disorder were medicated at the time of the study. The group studied was primarily female, so the observed effects may have been sex-specific. CONCLUSION: Rumination appears to be linked to altered self-related processing in depression, independent of stimuli-related emotional confounds. This connection between self-related processing and depression may point to a self disorder as a core component of depression.

Characterizing Self-Assembled Monolayer Breakdown in Area-Selective Atomic Layer Deposition.

To enable area-selective atomic layer deposition (AS-ALD), self-assembled monolayers (SAMs) have been used as the surface inhibitor to block a variety of ALD processes. The integrity of the SAM throughout the ALD process is critical to AS-ALD. Despite the demonstrated effectiveness of inhibition by SAMs, nucleation during ALD eventually occurs on SAM-protected surfaces, but its impact on SAM structures is still not fully understood. In this study, we chose the octadecyltrichlorosilane (ODTS) SAM as a model system to investigate the evolution of crystallinity and structure of SAMs before and after ALD. The breakdown behavior of SAMs when exposed to ZnO and Al2O3 ALD was systematically studied by combining synchrotron X-ray techniques and electron microscopy. We show that the crystallinity and structure of ODTS SAMs grown on Si substrates remain intact until a significant amount of material deposition takes place. In addition, the undesired ALD materials that grow on ODTS SAMs present contrasting morphologies: dispersed nanoparticles for ZnO while relatively continuous film for Al2O3. Lastly, substrate dependency was explored by comparing a Si substrate to single-crystal sapphire. Similar results in the evolution of SAM crystallinity and formation of ALD nuclei on top of SAM are observed in the ODTS-sapphire system. This study provides an in-depth view of the influence of ALD processes on the SAM structure and the nucleation behavior of ALD on SAM-protected surfaces.

Retrieval orientation for memories encoded in emotional contexts: An ERP study.

Retrieval orientation, which is involved in recognition cue processing, optimizes goal-directed memory retrieval. However, whether the emotionality of encoding context affects subsequent retrieval orientation remains unclear. To clarify this, neutral objects were paired with either emotional or neutral background scenes during the study phase. During recognition test, only neutral objects were presented. The ERP analysis on the correctly rejected new items indicated that at least two processes were modulated by the emotionality of memory: 1) the arousal-modulated effect on the right-frontal scalp, and 2) the posterior-distributed effect, which was found to differentiate between memories with positive and negative valence. Furthermore, the magnitude of posterior-distributed effect was correlated with affective rating. The topographical distribution indicated that retrieval orientation for positive memories involves at least partially different neural circuitries from neutral or negative memories. Our results suggest that the emotionality of encoding context affects subsequent retrieval orientation.

Effect of Multilayer versus Monolayer Dodecanethiol on Selectivity and Pattern Integrity in Area-Selective Atomic Layer Deposition.

Monolayer and multilayer dodecanethiols (DDT) can be assembled onto a copper surface from the vapor phase depending on the initial oxidation state of the copper. The ability of the copper-bound dodecanethiolates to block atomic layer deposition (ALD) and the resulting behavior at the interfaces of Cu/SiO2 patterns during area-selective ALD (AS-ALD) are compared between mono- and multilayers. We show that multilayer DDT is ∼7 times more effective at blocking ZnO ALD from diethylzinc and water than is monolayer DDT. Conversely, monolayer DDT exhibits better performance than does multilayer DDT in blocking of Al2O3 ALD from trimethylaluminum and water. Investigation into interfacial effects at the interface between Cu and SiO2 on Cu/SiO2 patterns reveals both a gap at the SiO2 edges and a pitch size-dependent nucleation delay of ZnO ALD on SiO2 regions of multilayer DDT-coated patterns. In contrast, no impact on ZnO ALD is observed on the SiO2 regions of monolayer DDT-coated patterns. We also show that these interfacial effects depend on the ALD chemistry. Whereas an Al2O3 film grows on the TaN diffusion barrier of a DDT-treated Cu/SiO2 pattern, the ZnO film does not. These results indicate that the structure of the DDT layer and the ALD precursor chemistry both play an important role in achieving AS-ALD.

Enhanced manual cleaning efficacy of duodenoscope in endoscopy units: Results of a multicenter comprehensive quality control program.

BACKGROUND: Multiple outbreaks from contaminated duodenoscopes have been reported since 2008. This study assessed results of a multicenter comprehensive quality control (QC) program to enhance manual cleaning efficacy of duodenoscopes in endoscopy units. METHODS: Digestive Endoscopy Society of Taiwan implemented a QC program with adenosine triphosphate (ATP) testing of patient-used duodenoscopes in 2 rounds of on-site audit in endoscopy units. ATP samples were obtained from 5 different locations of the duodenoscope after manual cleaning. Duodenoscope exceeding ATP benchmark of 200 relative light units indicated inadequate manual cleaning. RESULTS: During the first round on-site audit, 12 hospitals and 27 patient-used duodenoscopes were analyzed. Distal end outer surface (29.6%), elevator mechanism (51.9%), distal attachment cap (59.3%), elevator wire channel (37.0%), and suction biopsy channel (37.0%) were inadequately cleaned. Overall, 19 (70.4%) duodenoscopes had inadequate manual cleaning, ranging widely from 0%-100% among endoscopy units. During the follow-up on-site audit, 32 patient-used duodenoscopes were analyzed, and 6 (18.8%) had inadequate manual cleaning. CONCLUSIONS: ATP tests may provide real-time feedback on the cleaning efficacy of patient-used duodenoscopes. Implementing a comprehensive QC program could enhance the efficacy of manual cleaning in endoscopy units.

Selective rehearsal is affected by the emotionality of the encoding context in item-method directed forgetting: An event-related potential study.

Emotional items are often remembered more clearly than neutral items. However, whether stimuli embedded in an emotional context are more resistant to directed forgetting than those presented in a neutral context remains unclear. This question was tested by recording event-related potentials (ERPs) in an item-method directed forgetting paradigm involving neutral words that were embedded in neutral or negative contexts. During the study phase, participants were asked to associate a neutral word with a negative or neutral picture. A remember (R) or forget (F) cue was then designated to indicate whether the word was a to-be-remembered (TBR) or to-be-forgotten (TBF) word. In the test phase, participants were asked to identify all previously presented old words regardless of the R/F cues. The behavioral results indicated a significant interaction between the valence of the encoding contexts and the R/F cues. The hit rate was lower for the TBR words encoded in negative contexts relative to those encoded in neutral contexts. No such valence effect was observed in the hit rates of the TBF words. For the ERP data, the R cues elicited a P3b-like effect that has been linked to the selective rehearsal of the TBR items. This effect was more sustained in the negative encoding context than in the neutral context. The F cues elicited a frontal positivity that has been linked to the active inhibition of the TBF words; however, this positivity was not modulated by the valence of the encoding context. The sustained P3b-like effect for the R cues in the negative encoding context might reflect a compensative encoding for the TBR words caused by the attention-capturing negative contexts. Therefore, we argue that the emotional context affected the selective elaboration of the TBR words; however, we also argue that there was no supportive evidence of an emotional effect on the forgetting of TBF items.

Source memory performance is modulated by transcranial direct current stimulation over the left posterior parietal cortex.

This study employed transcranial direct current stimulation (tDCS) to examine whether the left posterior parietal cortex (LPPC) is causally involved in episodic memory retrieval. Thirty-six participants were assigned to the anodal or the cathodal stimulation group with the block-randomization method and engaged in three source memory tests on three separate days. During the test phase, the participants received anodal or cathodal stimulation over the LPPC scalp region in one visit, sham over the LPPC in another visit, and anodal or cathodal stimulation over the right primary motor cortex (M1) scalp region in the other visit. The results showed that source memory accuracy, but not old/new recognition performance, decreased significantly when participants in the cathodal group received stimulation over the LPPC scalp region in comparison to the other two stimulation conditions. No such effect was found in the anodal group. These findings provide evidence for the causal relationship between the LPPC and episodic memory retrieval.

The impact of spectral resolution on the mismatch response to Mandarin Chinese tones: an ERP study of cochlear implant simulations.

OBJECTIVE: This study examined the impact of spectral resolution on the processing of lexical tones and the number of frequency channels required for a cochlear implant (CI) to transmit Chinese tonal information to the brain. METHODS: ERPs were recorded in an auditory oddball task. Normal-hearing participants listened to speech sounds of two tones and their CI simulations in 1, 4, 8, or 32 channels. The mismatch response elicited by speech sounds and CI simulations in different numbers of channels were compared. RESULTS: The mismatch negativity (MMN) was observed for speech sounds. For the 1-channel CI simulations, deviants elicited a more positive waveform than standard stimuli. No MMN response was observed with the 4-channel simulations. A reliable MMN response was observed for the 8- and 32-channel simulations. The MMN responses elicited by the 8- and 32-channel simulations were equivalent in magnitudes and smaller than that elicited by speech sounds. CONCLUSIONS: More than eight frequency channels are required for a CI to transmit Chinese tonal information. The presence of both positive and negative mismatch responses suggests multiple mechanisms underlying auditory mismatch responses. SIGNIFICANCE: The current findings of spectral resolution constraints on the transmission of tonal information should be taken into account in the design of the CI devices.

Intentional forgetting reduces the semantic processing of to-be-forgotten items: an ERP study of item-method directed forgetting.

In two ERP experiments, we examined whether active inhibition is involved in intentional forgetting. Both experiments consisted of a nondirected-forgetting (nDF) and a directed-forgetting (DF) block. Participants were sequentially presented with a prime, an R/F (remember/forget) cue, and a target. Participants made lexical decisions to both the primes and targets (Experiment 1) or only to the targets (Experiment 2). They were also instructed to remember or to forget the primes in response to the R/F cues in the DF block but to ignore these cues in the nDF block. The N400 semantic priming effect was observed when comparing the ERPs elicited by semantically unrelated and related targets in the DF block. In comparison to the nDF block, the N400 effect was greatly reduced for targets preceded by F cues in the DF block. These findings suggest that semantic processing is reduced by the instruction to forget and active inhibition is involved in intentional forgetting.

Transforming growth factor-beta1 suppresses hepatitis B virus replication primarily through transcriptional inhibition of pregenomic RNA.

UNLABELLED: Transforming growth factor-beta1 (TGF-beta1) is a pleiotropic cytokine with pivotal roles in the regulation of cellular functions and immune responses. In this study, we found that TGF-beta1 was able to effectively suppress hepatitis B virus (HBV) replication. In the presence of TGF-beta1, the level of viral replicative intermediates was dramatically decreased, both in actively dividing cells and in confluent cells. At the same time, the levels of viral transcripts, core protein, and nucleocapsid were significantly diminished by TGF-beta1 treatment. Interestingly, the inhibitory activity of TGF-beta1 was associated with preferential reduction of the level of pregenomic RNA compared with pre-C mRNA. Further analysis indicated that TGF-beta1 might exert its antiviral effect primarily through reducing expression of the HBV core protein by transcriptional regulation instead of posttranscriptional modification. CONCLUSION: TGF-beta1 may play a dual role in HBV infection, in the suppression of immune responses against viral infection and in the direct inhibition of viral replication, resulting in minimization of liver damage in patients with chronic hepatitis.

Evaluation of transcriptional efficiency of hepatitis B virus covalently closed circular DNA by reverse transcription-PCR combined with the restriction enzyme digestion method.

Virus persistence in chronic hepatitis B patients is due to the sustaining level of covalently closed circular DNA (cccDNA) within the nuclei of infected hepatocytes. In this study, we used a modified 1.3-fold hepatitis B virus (HBV) genome, with a BclI genetic marker embedded in the redundancy region, to examine the transcriptional activity of cccDNA and the effect of the HBx protein on transcriptional regulation. After harvesting total RNA from transfected cells or stable lines, we specifically identified and monitored the transcripts from cccDNA by using reverse transcription-PCR (RT-PCR) combined with the restriction enzyme digestion method. In this approach, we have found that (i) RT-PCR combined with detection of the BclI marker is a highly specific method for distinguishing cccDNA-derived transcripts from the original integrated viral genome, (ii) the transcriptional ability of cccDNA was less efficient than that from the integrated viral genome, and (iii) the transcriptional activity of cccDNA was significantly regulated by the HBx protein, a potential transcription activator. In conclusion, we provided a tool with which to elucidate the transcriptional regulation of cccDNA and clarified the transcriptional regulation mechanism of HBx on cccDNA. The results obtained may be helpful in the development of a clinical intervention for patients with chronic HBV infections.