Impairment Mitigation Research Articles

Mitigation of Synaptic and Memory Impairments through F‐Actin Stabilization in an Alzheimer’s Disease Mouse Model

AbstractBackgroundF‐actin plays crucial roles in establishment and maintenance of synapses including post synaptic density organization, facilitation of vesicle trafficking, anchoring of postsynaptic receptors, and involvement in translational machinery. Proteomic analysis of actin‐interacting proteins revealed the interaction of PSD‐95 with actin in synaptosomes from brain cortex of APP/PS1 mice. PSD‐95 functions as a critical scaffold for the assembly of neurotransmitter receptors at the synapse, playing a pivotal role in regulating synaptic strength and plasticity. PSD‐95 directly interacts with NMDA receptors, whereas its interaction with AMPA receptors occurs through an auxiliary subunit, TARPs. The disruption in PSD‐95 association with actin observed in nine‐month‐old APP/PS1 mice may contribute to the synaptic neurotransmission deficit evident in the AD mouse model. Our objective here is to stabilize the F‐actin using Jasplakinolide to examine the disrupted interaction and assess its impact on synaptic function and memory impairment.MethodsNine‐month‐old wildtype and APP/PS1 mice were injected intrathecally with vehicle or Jasplakinolide (0.5µg/mice) and contextual fear conditioning memory was assessed 24 hours later. Following behavioral analysis, synaptosomes were isolated and examined for synaptic F‐actin levels and PSD‐95‐ actin association. Additionally, primary cortical cultures were treated with Jasplakinolide and analyzed for F‐actin intensity, dendritic spine density and AMPA receptor subunit surface localization.ResultsMemory recall and PSD‐95 association with actin is dysregulated in nine‐month‐old APP/PS1 mice compared to wildtype mice. However, injection of Jasplakinolide in APP/PS1 mice rescued the memory recall deficit. Synaptic F‐actin levels and the association of PSD‐95 with actin were restored in APP/PS1 mice received the Jasplakinolide. Primary cortical neurons, DIV21, derived from APP/PS1 mice showed a significant reduction in surface localization of AMPA receptor, F‐actin levels and dendritic spine density while these molecular events are restored by stabilization of F‐actin by Jasplakinolide.ConclusionThe compelling evidence supporting the stabilization of F‐actin suggests a promising strategy for alleviating synaptic impairments in AD, as it not only restores dendritic spines but also increases the surface localization of glutamate receptors. Our findings on complex interplay between cytoskeleton dynamics and synaptic functions may provide potential therapeutic targets aimed at preserving synaptic integrity and ameliorating cognitive decline in AD.

Mitigation of synaptic and memory impairments via F-actin stabilization in Alzheimer’s disease

BackgroundSynaptic dysfunction, characterized by synapse loss and structural alterations, emerges as a prominent correlate of cognitive decline in Alzheimer’s disease (AD). Actin cytoskeleton, which serves as the structural backbone of synaptic architecture, is observed to be lost from synapses in AD. Actin cytoskeleton loss compromises synaptic integrity, affecting glutamatergic receptor levels, neurotransmission, and synaptic strength. Understanding these molecular changes is crucial for developing interventions targeting synaptic dysfunction, potentially mitigating cognitive decline in AD.MethodsIn this study, we investigated the synaptic actin interactome using mass spectrometry in a mouse model of AD, APP/PS1. Our objective was to explore how alterations in synaptic actin dynamics, particularly the interaction between PSD-95 and actin, contribute to synaptic and cognitive impairment in AD. To assess the impact of restoring F-actin levels on synaptic and cognitive functions in APP/PS1 mice, we administered F-actin stabilizing agent, jasplakinolide. Behavioral deficits in the mice were evaluated using the contextual fear conditioning paradigm. We utilized primary neuronal cultures to study the synaptic levels of AMPA and NMDA receptors and the dynamics of PSD-95 actin association. Furthermore, we analyzed postmortem brain tissue samples from subjects with no cognitive impairment (NCI), mild cognitive impairment (MCI), and Alzheimer’s dementia (AD) to determine the association between PSD-95 and actin.ResultsWe found a significant reduction in PSD-95-actin association in synaptosomes from middle-aged APP/PS1 mice compared to wild-type (WT) mice. Treatment with jasplakinolide, an actin stabilizer, reversed deficits in memory recall, restored PSD-95-actin association, and increased synaptic F-actin levels in APP/PS1 mice. Additionally, actin stabilization led to elevated synaptic levels of AMPA and NMDA receptors, enhanced dendritic spine density, suggesting improved neurotransmission and synaptic strength in primary cortical neurons from APP/PS1 mice. Furthermore, analysis of postmortem human tissue with NCI, MCI and AD subjects revealed disrupted PSD-95-actin interactions, underscoring the clinical relevance of our preclinical studies.ConclusionOur study elucidates disrupted PSD-95 actin interactions across different models, highlighting potential therapeutic targets for AD. Stabilizing F-actin restores synaptic integrity and ameliorates cognitive deficits in APP/PS1 mice, suggesting that targeting synaptic actin regulation could be a promising therapeutic strategy to mitigate cognitive decline in AD.

Artificial Intelligence Models to Predict Disability for Mental Health Disorders

Early detection of mental health disorders allows specialists to provide more effective interventions, thereby improving the patient’s overall well-being. Mental health refers to the whole state of an individual’s psychological, emotional, and social well-being. Prompt detection of signs of mental disorders is essential for prompt intervention and the mitigation of recurrent symptoms and impairments. Therefore, artificial intelligence (AI) approaches have been used to aid mental health professionals, such as psychiatrists and psychologists, in making decisions by analyzing medical records and patients’ behavioral data. This research identified and evaluated the performance of machine learning algorithms, namely K-nearest neighbors (KNN), random forest (RF), and long short-term memory (LSTM), in detecting mental health conditions based on many accuracy criteria. A mental health disorder dataset was collected from Kaggel. The results of the implemented algorithms demonstrated that the RF approach attained an accuracy of 100%, while the KNN model scored an accuracy of 95%. The LSTM model achieved 99% accuracy with respect to the accuracy metric. The RF model attains an area under the curve of 100%. This system intends to use AI model methodologies to identify and predict mental health disorders at an early stage. This system is a well-established and effective tool that utilizes AI algorithms to accurately detect and diagnose various mental health illnesses, thus assisting in the decision-making process.

Learning and navigating digitally rendered haptic spatial layouts

Learning spatial layouts and navigating through them rely not simply on sight but rather on multisensory processes, including touch. Digital haptics based on ultrasounds are effective for creating and manipulating mental images of individual objects in sighted and visually impaired participants. Here, we tested if this extends to scenes and navigation within them. Using only tactile stimuli conveyed via ultrasonic feedback on a digital touchscreen (i.e., a digital interactive map), 25 sighted, blindfolded participants first learned the basic layout of an apartment based on digital haptics only and then one of two trajectories through it. While still blindfolded, participants successfully reconstructed the haptically learned 2D spaces and navigated these spaces. Digital haptics were thus an effective means to learn and translate, on the one hand, 2D images into 3D reconstructions of layouts and, on the other hand, navigate actions within real spaces. Digital haptics based on ultrasounds represent an alternative learning tool for complex scenes as well as for successful navigation in previously unfamiliar layouts, which can likely be further applied in the rehabilitation of spatial functions and mitigation of visual impairments.

Comparing distributed versus massed practice on functional recovery and Brain-Derived Neurotrophic Factor (BDNF) in acute stroke subjects.

Globally, stroke is known to be one of the major health problems, resulting in disability among an aging population. Rehabilitation is a process of re-learning of skills, lost due to brain injury. Many factors influence motor learning post neurological insult and practice is one of the key factors which influence relearning or reacquisition of lost motor skills. Practice can be varied concerning order (blocked or random), scheduling (massed or distributed), or whole and part practice. The study observed the effect of variations in practice schedules on motor and functional recovery. Thirty-two acute stroke subjects were recruited and equally divided into two groups (16 in massed and 16 in distributed). Both groups received an accelerated skill acquisition program (ASAP) for six sessions a week for 2 weeks. Pre- and post-outcome measures included stroke rehabilitation assessment of movement (STREAM) for motor recovery, modified Barthel index (MBI) for functional recovery, and brain-derived neurotrophic factor (BDNF) for neuroplasticity. The median scores of participants in the massed practice group before the intervention, of STREAM total, MBI, and BDNF were 23.5, 19, and 0.65, respectively, whereas post values of STREAM total, MBI, and BDNF were 40.5, 60.5, and 0.75, respectively. The median scores of the distributed practice group of the pre-STREAM total, MBI, and BDNF were 23.5, 6.5, and 0.70, respectively, whereas the post-STREAM total, MBI, and BDNF were 41, 45.5, and 0.80, respectively. P-value was reported to be <0.05 while comparing pre- and post-values of STREAM, MBI, and BDNF within both intervention groups. The median change scores of STREAM, MBI, and BDNF reported P ≥ 0.05 when compared between the groups. Both the groups had significant recovery post-intervention designed based on ASAP, about impairment mitigation, pursuing skilled movement leading to significant functional gains. Appropriate timing along with optimal dosage became an active ingredient in functional recovery in acute stroke subjects. The distributed practice might have added effect of spacing, resulting in easier learning and accuracy of skills. The study reveals that distributed practice can be part of regular clinical practice to enhance functional recovery in acute stroke rehabilitation.

Effect of acetate supplementation on traumatic stress-induced behavioral impairments in male rats

Gut microbiota and their metabolites have emerged as key players in the pathogenesis of neuropsychiatric disorders. Recently, we demonstrated that animals susceptible to Single Prolonged Stress (SPS) have an overall pro-inflammatory gut microbiota and significantly lower cecal acetate levels than SPS-resilient rats, which correlated inversely with the anxiety index. Here, we investigated whether the microbial metabolite, acetate, could ameliorate SPS-triggered impairments. Male rats were randomly divided into unstressed controls or groups exposed to SPS. The groups received continued oral supplementation of either 150 mM of sodium acetate or 150 mM of sodium chloride-matched water. Two weeks after SPS, a battery of behavioral tests was performed, and the animals were euthanized the following day. While not affecting the unstressed controls, acetate supplementation reduced the impact of SPS on body weight gain and ameliorated SPS-induced anxiety-like behavior and the impairments in social interaction, but not depressive-like behavior. These changes were accompanied by several beneficial effects of acetate supplementation. Acetate alleviated the stress response by reducing urinary epinephrine levels, induced epigenetic modification by decreasing histone deacetylase (HDAC2) gene expression, inhibited neuroinflammation by reducing the density of Iba1+ cells and the gene expression of IL-1ß in the hippocampus, and increased serum β-hydroxybutyrate levels. The findings reveal a causal relationship between oral acetate treatment and mitigation of several SPS-induced behavioral impairments. Mechanistically, it impacted neuronal and metabolic pathways including changes in stress response, epigenetic modifications, neuroinflammation and showed novel link to ketone body production. The study demonstrates the preventive-therapeutic potential of acetate supplementation to alleviate adverse responses to traumatic stress.

Recurrent Neural Networks and Recurrent Optical Spectrum Slicers as Equalizers in High Symbol Rate Optical Transmission Systems

The transition to the edge-cloud era makes ultra-high data rate signals indispensable for covering the immense and increasing traffic demands created. This ecosystem also seeks for power efficient optical modules that will deliver this enormous data load. Optical communication systems and their continuous evolution have responded to the upward trend of capacity needs in all different network ecosystems, scaling from short-reach links serving data center, fiber-to-the-home and 5G/B5G services to metro and long-haul transoceanic cables. Kerr induced non-linearities at long haul and dispersion induced power fading at short reach remain intractable problems that vastly affect high symbol rate systems. So, they must be addressed in a power efficient way in order to cope with the ever-increasing traffic requirements. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this paper, we review our recent work in machine learning and neuromorphic processing in the optical domain for the mitigation of transmission impairments at very high symbol rates. Post-detection techniques based on bidirectional recurrent neural networks for non-linearity compensation and neuromorphic recurrent optical spectrum slicers for power fading mitigation and self-coherent detection emerge as promising solutions for mid-term deployment in long-haul and short-reach communication systems respectively. The current work provides new results in both fields focusing on multi-channel detection in the coherent long-haul domain and on a cost/consumption/performance assessment of neuromorphic photonic processing based on recurrent spectrum slicing in comparison to the state-of-the-art. A thorough analysis of other state-of-the-art techniques in both domains is also provided revealing the merits and shortcomings of recurrent neural networks and neuromorphic photonic processing in high-speed optical communication systems.

Reducing Computational Complexity of Neural Networks in Optical Channel Equalization: From Concepts to Implementation

In this paper, a new methodology is proposed that allows for the low-complexity development of neural network (NN) based equalizers for the mitigation of impairments in high-speed coherent optical transmission systems. In this work, we provide a comprehensive description and comparison of various deep model compression approaches that have been applied to feed-forward and recurrent NN designs. Additionally, we evaluate the influence these strategies have on the performance of each NN equalizer. Quantization, weight clustering, pruning, and other cutting-edge strategies for model compression are taken into consideration. In this work, we propose and evaluate a Bayesian optimization-assisted compression, in which the hyperparameters of the compression are chosen to simultaneously reduce complexity and improve performance. Next, this paper presents four distinct metrics (RMpS, BoP, NABS, and NLGs) that are discussed here that can be used to evaluate the amount of computing complexity required by various compression algorithms. These measurements can serve as a benchmark for evaluating the relative effectiveness of various NN equalizers when compression approaches are used. In conclusion, the trade-off between the complexity of each compression approach and its performance is evaluated by utilizing both simulated and experimental data in order to complete the analysis. By utilizing optimal compression approaches, we show that it is possible to design an NN-based equalizer that is simpler to implement and has better performance than the conventional digital back-propagation (DBP) equalizer with only one step per span. This is accomplished by reducing the number of multipliers used in the NN equalizer after applying the weighted clustering and pruning algorithms. Furthermore, we demonstrate that an equalizer based on NN can also achieve superior performance while still maintaining the same degree of complexity as the full electronic chromatic dispersion compensation block. We conclude our analysis by highlighting open questions and existing challenges, as well as possible future research directions.

Measurement of Total Dissolved Solids and Total Suspended Solids in Water Systems: A Review of the Issues, Conventional, and Remote Sensing Techniques

This study provides a comprehensive review of the efforts utilized in the measurement of water quality parameters (WQPs) with a focus on total dissolved solids (TDS) and total suspended solids (TSS). The current method used in the measurement of TDS and TSS includes conventional field and gravimetric approaches. These methods are limited due to the associated cost and labor, and limited spatial coverages. Remote Sensing (RS) applications have, however, been used over the past few decades as an alternative to overcome these limitations. Although they also present underlying atmospheric interferences in images, radiometric and spectral resolution issues. Studies of these WQPs with RS, therefore, require the knowledge and utilization of the best mechanisms. The use of RS for retrieval of TDS, TSS, and their forms has been explored in many studies using images from airborne sensors onboard unmanned aerial vehicles (UAVs) and satellite sensors such as those onboard the Landsat, Sentinel-2, Aqua, and Terra platforms. The images and their spectral properties serve as inputs for deep learning analysis and statistical, and machine learning models. Methods used to retrieve these WQP measurements are dependent on the optical properties of the inland water bodies. While TSS is an optically active parameter, TDS is optically inactive with a low signal–noise ratio. The detection of TDS in the visible, near-infrared, and infrared bands is due to some process that (usually) co-occurs with changes in the TDS that is affecting a WQP that is optically active. This study revealed significant improvements in incorporating RS and conventional approaches in estimating WQPs. The findings reveal that improved spatiotemporal resolution has the potential to effectively detect changes in the WQPs. For effective monitoring of TDS and TSS using RS, we recommend employing atmospheric correction mechanisms to reduce image atmospheric interference, exploration of the fusion of optical and microwave bands, high-resolution hyperspectral images, utilization of ML and deep learning models, calibration and validation using observed data measured from conventional methods. Further studies could focus on the development of new technology and sensors using UAVs and satellite images to produce real-time in situ monitoring of TDS and TSS. The findings presented in this review aid in consolidating understanding and advancement of TDS and TSS measurements in a single repository thereby offering stakeholders, researchers, decision-makers, and regulatory bodies a go-to information resource to enhance their monitoring efforts and mitigation of water quality impairments.

Requirements and Solutions for Robust Beam Alignment in Fiber-Coupled Free-Space Optical Systems

The continuous growth of Internet data traffic is pushing the current radio-frequency wireless technologies up to their physical limits. To overcome the upcoming bandwidth bottleneck, Free-Space Optics (FSO) is currently deemed as a key breakthrough toward next-generation ultra-high-capacity wireless links. Despite its numerous advantages, FSO also entails several particular challenges regarding the mitigation of the stochastic impairments induced by turbulence and the strict alignment requirements. One of the main issues of FSO communication systems is the mitigation of pointing errors and angle-of-arrival (AoA) fluctuations, which arise from misalignments induced by atmospheric turbulence and vibrations at the transmitting and receiving stations. A common approach to mitigate the impact of pointing errors is the use of an acquisition, tracking and pointing (ATP) system on one or both ends of the FSO link. In this paper, we present a characterization of the pointing errors and the AoA impact on the power budget of the FSO link to quantify the misalignment impairments. Afterwards, we experimentally demonstrate an FSO link with an ATP mechanism at both ends, managed by a control plane that enables the continuous and accurate alignment of the FSO link. To increase the misalignment tolerance, the ATP mechanism comprises two stages: the first one is based on a spatial diversity method provided by a quadrant detector, while the second stage maximizes the optical received power. Lastly, the impact of the beam misalignment on the achievable information rate of a coherent optical wireless system is theoretically addressed and characterized.

Event-related causality in stereo-EEG discriminates syntactic processing of noun phrases and verb phrases

Objective. Syntax involves complex neurobiological mechanisms, which are difficult to disentangle for multiple reasons. Using a protocol able to separate syntactic information from sound information we investigated the neural causal connections evoked by the processing of homophonous phrases, i.e. with the same acoustic information but with different syntactic content. These could be either verb phrases (VP) or noun phrases. Approach. We used event-related causality from stereo-electroencephalographic recordings in ten epileptic patients in multiple cortical and subcortical areas, including language areas and their homologous in the non-dominant hemisphere. The recordings were made while the subjects were listening to the homophonous phrases. Main results. We identified the different networks involved in the processing of these syntactic operations (faster in the dominant hemisphere) showing that VPs engage a wider cortical and subcortical network. We also present a proof-of-concept for the decoding of the syntactic category of a perceived phrase based on causality measures. Significance. Our findings help unravel the neural correlates of syntactic elaboration and show how a decoding based on multiple cortical and subcortical areas could contribute to the development of speech prostheses for speech impairment mitigation.

Performance evaluation of fiber impairment mitigation for high capacity communication systems using optical compensation method

Due to their ability to boost transmission rate and reach by compensating for Kerr nonlinearity-induced distortions, optical compensation techniques are interesting for broadband wavelength division multiplexing. This is due to the fact that these techniques have been shown to increase transmission rate. Yet, in the majority of instances, they call for more devices to be integrated into the network. This can be challenging for systems that are already in place, and it can be even more challenging for transmissions that are not repeated. The linear and nonlinear compensation system for the Dense Wave Division Multiplexing (DWDM) transmission system has been created and researched in this work. Along the optical link, a new method known as optical phase conjugation (OPC) is used as part of the process of improving the performance of communication systems. This method is used to improve the performance of 896 Gb/s sixteen channels dual polarization signalling of 50 GHz channel spacing over 800 km with three scenarios that use mid and multiple OPC. The results of the simulation indicate that multiple OPC with backward Raman amplifier method on the received signal is effective for nonlinearity compensation when compared with the mid OPC module in terms of enhanced Q-factor improvement, BER performance, EVM, and maximum transmission link length.

Apigenin: Exploring its neuroprotective potential in neurodegenerative disorders: Mechanisms and promising therapeutic applications

Neurodegenerative diseases pose significant challenges to global health-care systems, highlighting the urgent need for effective therapeutic strategies. Apigenin (API), a natural compound derived from various plant sources, has emerged as a potential treatment option due to its neuroprotective properties. This review article provides a comprehensive overview of API, focusing on its definition, natural sources, pharmacokinetics, and bioavailability, mechanisms of action, safety, and tolerability profile. API protects neurons in many ways, including its antioxidant activity, anti-inflammatory properties, ability to change cellular signaling pathways, ability to stop proteins from misfolding and sticking together, and ability to improve mitochondrial function. In vitro studies have demonstrated that API attenuates oxidative stress, inhibits the formation of protein aggregates, and suppresses neuroinflammation. Animal models, such as transgenic mice, rat models, and non-human primates, have provided valuable insights into the potential therapeutic benefits of API, including improved cognitive function, mitigation of motor impairments, and preservation of neuronal integrity. API’s safety and tolerability profile appears favorable based on preclinical and clinical studies, with minimal reported adverse effects. However, further investigation is required to determine optimal dosing regimens and assess potential drug interactions. In addition, while current treatment options for neurodegenerative diseases primarily focus on symptom management, API holds promise as a disease-modifying agent.

Independent component analysis for impairment mitigation in direct-detected Stokes vector modulation.

In this paper we theoretically and experimentally demonstrate a novel adaptation of independent component analysis (ICA) for compensation of both cross-polarization and inter-symbol interference in a direct-detection link using Stokes vector modulation (SVM). SVM systems suffer from multiple simultaneous impairments that can be difficult to resolve with conventional optical channel DSP techniques. The proposed method is based on a six-dimensional adaptation of ICA that simultaneously de-rotates the SVM constellation, corrects distortion of constellation shape, and mitigates inter-symbol interference (ISI) at high symbol rates. Experimental results at 7.5 Gb/s and 15Gb/s show that the newly developed ICA-based equalizer achieves power penalties below ∼1 dB, compared to the ideal theoretical bit-error rate (BER) curves. At 30-Gb/s, where ISI is more severe, ICA still enables polarization de-rotation and BER < 10-5 before error correction.

QCOB: a novel QPSK coherent optical OFDM modulation technique for mitigation of fiber impairments

Abstract Modern optical communication heavily relies on coherent optical orthogonal frequency division multiplexing (CO-OFDM) modulation. But the usage of optical OFDM for fiber optic communication is still constrained in comparison to other modes of communication like visible light communication (VLC) and wireless communication due to a number of issues such as various sorts of fiber impairments including dispersion and attenuation. In this research paper, a novel optical OFDM modulation technique has been proposed. It is quadrature phase shift keying (QPSK) CO-OFDM modulation with Bessel optical filter in fiber optical link and is named as QCOB. This modulation technique works for optical fiber transmission. Its testing has been carried out for parameters like bit error rate (BER) and quality-factor (Q-factor) over a range of fiber length, fiber dispersion coefficient and input power. This modulation employs coherent optical OFDM with QPSK for subcarrier modulation. The optical link utilizes a Bessel optical filter. Improved results have been achieved over conventional QPSK CO-OFDM (QCO). The obtained results demonstrate the superiority of the QCOB technique in terms of performance enhancement and fiber impairment reduction. In comparison to the QCO technique, the BER performance (reduction in BER) of the QCOB technique shows an improvement of around 7.4, 100, 14.4, 46.4 and 3.4% for dispersion coefficient values of 10, 20, 30, 50 and 100 (in ps/nm-km), respectively.

Mitigation of fiber impairments by developing a novel coherent optical 16-QAM OFDM modulation technique

Mitigation of fiber impairments by developing a novel coherent optical 16-QAM OFDM modulation technique

Advanced Digital Signal Processing and Variable-Rate Coding for Unrepeatered Optical Transmission

In this paper, we evaluate the selective combination of algorithms for fiber nonlinearity compensation, transceiver impairments mitigation and variable-rate coding in unrepeatered optical transmission. A post-emphasis filter and a two-stage 4×4 multiple-input and multiple-output equalizer compensate the impact of bandwidth limitations and in-phase and quadrature skew. Nonlinear compensation is accomplished by a fast-converging adaptive digital back-propagation algorithm and maximum likelihood sequence estimation. Forward error correction is provided by a variable-rate spatially-coupled low-density parity-check code. The performance and complexity of the proposed digital subsystems are experimentally evaluated by the unrepeatered wavelength division multiplexing transmission of 17×200-Gb/s (DP-16QAM 32-GBd) channels over 350-km of large effective area and low-loss single-mode fibers. The experimental results for different combinations of algorithms elucidate the trade-off of complexity and performance in unrepeatered optical transmission.

Transceiver Impairment Mitigation by 8×2 Widely Linear MIMO Equalizer With Independent Complex Filtering on IQ Signals

High-order modulation formats with high symbol rates are promising candidates for meeting the growing traffic requirements of digital coherent transmission. In using these modulation formats, the impact of transceiver impairment on the signal quality becomes significant. In this paper, we propose an 8×2 widely linear (WL) multiple-input multiple-output (MIMO) equalizer with independent complex filtering on IQ signals to mitigate linear transceiver impairments. Furthermore, we extend the equalizer for digital subcarrier (SC) multiplexing. Accordingly, a 16×4 WL MIMO equalizer is also proposed to mitigate linear transceiver impairments, through application to a pair of SC inputs. Experimental results show that, for transmission of a 58-GBaud polarization-multiplexing 64 quadrature amplitude modulation (PM-64QAM) single-carrier signal, the proposed method effectively compensates for various receiver impairments and also mitigates transmitter (Tx) impairments. Q-penalties of 0.1 dB up to a 10-ps skew, 2.5-dB gain imbalance, 7.2-degree phase error, and –15-dB crosstalk in Tx were achieved for 100-km standard single-mode fiber transmission. Moreover, for a 29-GBaud PM-64QAM dual-SC signal, the proposed 16 × 4 WL MIMO equalizer shows transceiver impairment mitigation performance similar to that in the single-carrier case, even though dual-SC transmission is less tolerant of laser phase noise.

Characterization, Monitoring, and Mitigation of the I/Q Imbalance in Standard C-Band Transceivers in Multi-Band Systems

Next-generation optical communication networks aim to vastly increase capacity by exploiting a larger optical transmission window covering the S-C-L-band. Simultaneously, the clear market trend is to maximize capacity per wavelength to reduce operational costs. This approach requires an increase in spectral efficiency, resulting in stringent requirements on the transceivers, which may not be satisfied in a multi-band (MB) scenario by current commercial components designed for operation in C-band. Transceiver specifications for MB operation can be relaxed through additional digital signal processing (DSP), at the cost of additional complexity, and by more resource-intensive calibration procedures. In this context, we experimentally characterize the wavelength-dependent frequency-resolved in-phase/quadrature (I/Q) imbalance of a standard C-band IQ-modulator and coherent receiver operating in an S-C-L-band system utilizing receiver-side DSP. This operation allows us to understand the nature of the wavelength-dependency of I/Q imbalance in MB systems. In the considered scenario, we validate the effectiveness of a cost-effective strategy for transceiver impairments mitigation and monitoring based on standard wavelength-independent calibration and reduced-complexity DSP.

Pediatric vascular anomalies with airway compromise.

Vascular anomalies are rare lesions of diverse nature that may affect the head and neck region. Any mass in or around the upper airway has the potential to obstruct or compromise it. The absolute priority, before etiologic treatment, is the evaluation of the risk for the airway and its management. Prenatal diagnosis of an upper airway obstruction requires a planned delivery in a center having a specialized team experienced in managing a compromised feto-neonatal airway, and who could perform an ex-utero intrapartum treatment to secure the airway. Even after birth, the airway remains central in the patient's overall management. Signs and symptoms of airway compromise must be evaluated keeping in mind the specific requirements of infants and small children and being aware that rapid worsening may occur. The treatment is then tailored to the patient and his lesion with the goal of improving symptoms while avoiding treatment-related complications. Maintaining reasonable expectations by the patient and families are part of a successful management. Cure is achievable for small and localized lesions, but symptom relief and mitigation of functional, esthetic and psychological impairments is the goal for large and complex lesions. If a tracheotomy was required, decannulation is one of the primary management goals.