The integrated information theory (IIT) proposes a quantitative measure, denoted as Φ, of the amount of integrated information in a physical system, which is postulated to have an identity ...relationship with consciousness. IIT predicts that the value of Φ estimated from brain activities represents the level of consciousness across phylogeny and functional states. Practical limitations, such as the explosive computational demands required to estimate Φ for real systems, have hindered its application to the brain and raised questions about the utility of IIT in general. To achieve practical relevance for studying the human brain, it will be beneficial to establish the reliable estimation of Φ from multichannel electroencephalogram (EEG) and define the relationship of Φ to EEG properties conventionally used to define states of consciousness. In this study, we introduce a practical method to estimate Φ from high-density (128-channel) EEG and determine the contribution of each channel to Φ. We examine the correlation of power, frequency, functional connectivity, and modularity of EEG with regional Φ in various states of consciousness as modulated by diverse anesthetics. We find that our approximation of Φ alone is insufficient to discriminate certain states of anesthesia. However, a multi-dimensional parameter space extended by four parameters related to Φ and EEG connectivity is able to differentiate all states of consciousness. The association of Φ with EEG connectivity during clinically defined anesthetic states represents a new practical approach to the application of IIT, which may be used to characterize various physiological (sleep), pharmacological (anesthesia), and pathological (coma) states of consciousness in the human brain.
Purpose
To develop a free‐breathing, non‐electrocardiogram technique for simultaneous myocardial T1, T2, T2*, and fat‐fraction (FF) mapping in a single scan.
Methods
The MR Multitasking framework is ...adapted to quantify T1, T2, T2*, and FF simultaneously. A variable TR scheme is developed to preserve temporal resolution and imaging efficiency. The underlying high‐dimensional image is modeled as a low‐rank tensor, which allows accelerated acquisition and efficient reconstruction. The accuracy and/or repeatability of the technique were evaluated on static and motion phantoms, 12 healthy volunteers, and 3 patients by comparing to the reference techniques.
Results
In static and motion phantoms, T1/T2/T2*/FF measurements showed substantial consistency (R > 0.98) and excellent agreement (intraclass correlation coefficient > 0.93) with reference measurements. In human subjects, the proposed technique yielded repeatable T1, T2, T2*, and FF measurements that agreed with those from references.
Conclusions
The proposed free‐breathing, non‐electrocardiogram, motion‐resolved Multitasking technique allows simultaneous quantification of myocardial T1, T2, T2*, and FF in a single 2.5‐min scan.
Introduction
We describe a case of acute exudative polymorphous vitelliform maculopathy (AEPVM) that recurred 9 years after the initial event. To the best of our knowledge, this is the first report ...of recurrent AEPVM showing recovery of retinal and retinal pigment epithelium (RPE) function and good visual outcome following treatment with intravitreal corticosteroid.
Case description
A 45-year-old Caucasian woman first presented with AEVPM in 2009. Her condition spontaneously resolved and she remained stable over several years. 9 years later, her condition recurred with bilateral reduction in visual acuity. Fundus examination revealed multiple small yellowish subretinal lesions across the posterior pole in both eyes. Optical coherence tomography (OCT) showed bilateral cystoid macular oedema (CMO). She was referred for electrophysiology and her electrooculogram findings were in keeping with severe generalised RPE dysfunction bilaterally, with a light peak to dark trough ratio (Arden index) of 110%, comparable to her initial presentation 9 years earlier. She was initially treated with oral steroids with some improvement. However, the maculopathy in the left eye recurred on cessation of oral treatment. A sustained-release 700ug dexamethasone intravitreal implant (Ozurdex®) was inserted in the left eye to which she responded remarkably, with improvement in visual acuity and complete resolution of the CMO. A year later, at her most recent clinic visit in March 2021, there was no evidence of any further recurrence.
Conclusion
Our case demonstrates clinical and imaging findings consistent with recurrence of AEPVM with CMO that has been successfully treated with Ozurdex®.
CueO from Escherichia coli is a multicopper oxidase (MCO) involved in copper tolerance under aerobic conditions. It features four copper atoms that act as electron transfer (T1) and dioxygen ...reduction (T2, T3; trinuclear) sites. In addition, it displays a methionine-rich insert which includes a helix that blocks physical access to the T1 site and which provides an extra labile site T4 adjacent to the T1 center. This T4 site is required for CueO function. Like many MCOs, CueO exhibits phenol oxidase activity with broad substrate specificity. Maximal activity with model substrate 2,6-dimethoxyphenol required stoichiometric occupation of T4 by CuII (notation: CuII-CueO). This was achieved in Mops buffer which has little affinity for Cu2+. However, pH buffers that bind or precipitate Cu2+ (Tris, BisTris, and KPi) generated enzyme with a vacant T4 site (notation: ◻-CueO) which has no phenol oxidase activity. Addition of excess Cu2+ effectively generated a Cu2+ buffer and recovered the activity partially or completely, depending upon the specific pH buffer. This phenomenon allowed reliable estimation of the affinity of T4 for CuII: K D = 5.5 × 10−9 M. CueO is involved in copper tolerance and has been suggested to be a cuprous oxidase. The anion CuI(Bca)23− (Bca = bicinchoninate) acted as a novel chromophoric substrate. It is a robust reagent, being air-stable and having a CuI affinity comparable to those of periplasmic CuI binding proteins. The influences of pH buffer composition and of excess Cu2+ on cuprous oxidation were diametrically opposite to those seen for phenol oxidation, suggesting that ◻-CueO, not CuII-CueO, is the resting form of the cuprous oxidase. Steady-state kinetics demonstrated that the intact anion CuI(Bca)23−, not “free” Cu+, is the substrate that donates CuI directly to T4. The data did not follow classical Michaelis−Menten kinetics but could be fitted satisfactorily by an extension that considered the effect of free ligand Bca. The K m term consists of two components, allowing estimation of the transient affinity of T4 for CuI: K D = 1.3 × 10−13 M. It may be concluded that CuI carried by CuI(Bca)23− is oxidized only upon complete transfer of CuI to T4. The transfer is required to induce a negative shift in the copper reduction potential to allow oxidation and electron transfer to the T1 site. The results provide compelling evidence that CueO is a cuprous oxidase. The new approach will have significant application to the study of metallo-oxidase enzymes.
Purpose
To develop a dynamic contrast‐enhanced (DCE) MRI method capable of high spatiotemporal resolution, 3D carotid coverage, and T1‐based quantification of contrast agent concentration for the ...assessment of carotid atherosclerosis using a newly developed Multitasking technique.
Methods
5D imaging with 3 spatial dimensions, 1 T1 recovery dimension, and 1 DCE time dimension was performed using MR Multitasking based on low‐rank tensor modeling, which allows direct T1 quantification with high spatiotemporal resolution (0.7 mm isotropic and 595 ms, respectively). Saturation recovery preparations followed by 3D segmented fast low angle shot readouts were implemented with Gaussian‐density random 3D Cartesian sampling. A bulk motion removal scheme was developed to improve image quality. The proposed protocol was tested in phantom and human studies. In vivo scans were performed on 14 healthy subjects and 7 patients with carotid atherosclerosis. Kinetic parameters including area under the concentration versus time curve (AUC), vp, Ktrans, and ve were evaluated for each case.
Results
Phantom experiments showed that T1 measurements using the proposed protocol were in good agreement with reference value (R2=0.96). In vivo studies demonstrated that AUC, vp, and Ktrans in the patient group were significantly higher than in the control group (0.63 ± 0.13 versus 0.42 ± 0.12, P < 0.001; 0.14 ± 0.05 versus 0.11 ± 0.03, P = 0.034; and 0.13 ± 0.04 versus 0.08 ± 0.02, P < 0.001, respectively). Results from repeated subjects showed good interscan reproducibility (intraclass correlation coefficient: vp, 0.83; Ktrans, 0.87; ve, 0.92; AUC, 0.94).
Conclusion
Multitasking DCE is a promising approach for quantitatively assessing the vascularity properties of the carotid vessel wall.
In a cerebral hypometabolic state, cortical neurons exhibit slow synchronous oscillatory activity with sparse firing. How such a synchronization spatially organizes as the cerebral metabolic rate ...decreases have not been systemically investigated. We developed a network model of leaky integrate-and-fire neurons with an additional dependency on ATP dynamics. Neurons were scattered in a 2D space, and their population activity patterns at varying ATP levels were simulated. The model predicted a decrease in firing activity as the ATP production rate was lowered. Under hypometabolic conditions, an oscillatory firing pattern, that is, an ON-OFF cycle arose through a failure of sustainable firing due to reduced excitatory positive feedback and rebound firing after the slow recovery of ATP concentration. The firing rate oscillation of distant neurons developed at first asynchronously that changed into burst suppression and global synchronization as ATP production further decreased. These changes resembled the experimental data obtained from anesthetized rats, as an example of a metabolically suppressed brain. Together, this study substantiates a novel biophysical mechanism of neuronal network synchronization under limited energy supply conditions.
To test the hypotheses that hypertension and nocturnal blood pressure are related to white matter hyperintensity (WMH) volume, an MRI marker of small vessel cerebrovascular disease, and that WMH ...burden statistically mediates the association of hypertension and dipping status with memory functioning, we examined the relationship of hypertension and dipping status on WMH volume and neuropsychological test scores in middle-aged and older adults.
Participants from the community-based Maracaibo Aging Study received ambulatory 24-hour blood pressure monitoring, structural MRI, and neuropsychological assessment. Four hundred thirty-five participants (mean ± SD age 59 ± 13 years, 71% women) with available ambulatory blood pressure, MRI, and neuropsychological data were included in the analyses. Ambulatory blood pressure was used to define hypertension and dipping status (i.e., dipper, nondipper, and reverse dipper based on night/day blood pressure ratio <0.9, 0.9-1, and >1, respectively). Outcome measures included regional WMH and memory functioning derived from a neuropsychological test battery.
The majority of the participants (59%) were hypertensive. Ten percent were reverse dippers, and 40% were nondippers. Reverse dipping in the presence of hypertension was associated with particularly elevated periventricular WMH volume (
= 3.78,
= 0.024) and with lowered memory scores (
= 3.911,
= 0.021). Periventricular WMH volume mediated the effect of dipping status and hypertension on memory (β = -4.1, 95% confidence interval -8.7 to -0.2,
< 0.05).
Reverse dipping in the presence of hypertension is associated with small vessel cerebrovascular disease, which, in turn, mediates memory functioning. These results point toward reverse dipping as a marker of poor nocturnal blood pressure control, particularly among hypertensive individuals, with potentially pernicious effects on cerebrovascular health and associated cognitive function.
An electrical impedance spectroscopy fouling monitor (EISFM) was used to monitor the performance of a reverse osmosis (RO) treatment train in a NEWater plant in Singapore. A ‘canary cell’ equipped ...with an EIS measurement system was installed in a side stream of the train. It was operated at the same hydrodynamics as the train to simulate the fouling conditions in the spiral wound modules. The correlation between the EISFM response and plant performance was investigated. When trending the real part of the impedance of the low frequency signal element (Zreal-DP) over time, there was a maximum in the normalised Zreal-DP observed well before chemical cleaning which was indicated by the traditional operational criteria. The occurrence of Zreal-DP peaks can be used as an indicator to initiate mitigation measures, such as adjustment of flux or crossflow velocity. As such, the frequency of chemical CIPs could be reduced. Furthermore, by observing the trend of Zreal-DP over time, it was possible to identify the nature of the fouling such as the build-up of a layer of inorganic colloids. This was validated by membrane autopsy studies. This study confirms that the EISFM is suitable for monitoring the performance of RO in a real plant.
•EISFM was used to monitor the performance of RO train in Singapore NEWater plant.•Maximum in the normalised Zreal-DP was observed well before CIPs were carried out.•Mitigation measures could be initiated based on the occurrence of Zreal-DP peaks.•The frequency of CIPs could be reduced by implementing physical control measures.•The nature of fouling layer could be identified from the trend of Zreal-DP.
Two independent atmospheric general circulation models reveal that the positive (negative) phase of Atlantic multidecadal variability (AMV) can reduce (amplify) the variance of the shorter time-scale ...(e.g., ENSO related) precipitation fluctuations in the United States, especially in the Southwest, as well as decrease (increase) the long-term seasonal mean precipitation for the cold season. The variance is modulated because of changes in 1) dry day frequency and 2) maximum daily rainfall intensity. With positive AMV forcing, the upper-level warming originating from the increased precipitation over the tropical Atlantic Ocean changes the mean vertical thermal structure over the United States continent to a profile less favorable for rain-inducing upward motions. In addition, a northerly low-level dry advection associated with the local overturning leaves less available column moisture for condensation and precipitation. The opposite conditions occur during cold AMV periods.
Electrical impedance spectroscopy (EIS) has been used as a non-invasive means of characterising the electrical properties of a reverse osmosis (RO) membrane during fouling and cleaning processes. The ...crossflow RO unit used in this study was equipped with suitable electrodes and used in conjunction with a high resolution impedance spectroscope that allowed changes in the electrical properties of the membrane and foulant layer to be monitored. The internal structure of the membrane could be represented by a series combination of parallel conductance and capacitance elements. The deduced support layer thickness matched optical measurements and the effective polyamide skin layer thickness matched recently reported data using high resolution TEM. During the filtration process using silica and alginate as model foulants, the conductance of all the electrical elements initially decreased with time and then increased as fouling progressed. The increase was associated with a local increase in salinity due to the development of cake enhanced concentration polarization. The capacitance of the skin layer decreased as the fouling process progressed and this could be evidence of the built up of foulant layers on membrane surface. By flushing the fouled membrane with NaCl solution for about 17h, the membrane returned back to its original state, with its capacitance and conductance values similar to the unfouled membrane.
•Electrical impedance spectroscopy (EIS) used for in-situ fouling detection in RO.•Impedance spectra of membrane process consist of four Maxwell–Wagner elements.•EIS parameters: capacitance and conductance were quantified and studied.•EIS data is used to understand fouling and cleaning behavior of silica/alginate.
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