Phototransformation of achiral metasurfaces into handedness-selectable transient chiral media.

Chirality is a geometric property describing the lack of mirror symmetry. This unique feature enables photonic spin-selectivity in light-matter interaction, which is of great significance in stereochemistry, drug development, quantum optics, and optical polarization control. The versatile control of optical geometry renders optical metamaterials as an effective platform for engineered chiral properties at prescribed spectral regimes. Unfortunately, geometry-imposed restrictions only allow one circular polarization state of photons to effectively interact with chiral meta-structures. This limitation motivates the idea of discovering alternative techniques for dynamically reconfiguring the chiroptical responses of metamaterials in a fast and facile manner. Here, we demonstrate an approach that enables optical, sub-picosecond conversion of achiral meta-structures to transient chiral media in the visible regime with desired handedness upon the inhomogeneous generation of plasmonic hot electrons. As a proof of concept, we utilize linearly polarized laser pulse to demonstrate near-complete conversion of spin sensitivity in an achiral meta-platform-a functionality yet achieved in a non-mechanical fashion. Owing to the generation, diffusion, and relaxation dynamics of hot electrons, the demonstrated technique for all-optical creation of chirality is inherently fast, opening new avenues for ultrafast spectro-temporal construction of chiral platforms with on-demand spin-selectivity.

Determining hot-carrier transport dynamics from terahertz emission.

Understanding the ultrafast excitation and transport dynamics of plasmon-driven hot carriers is critical to the development of optoelectronics, photochemistry, and solar-energy harvesting. However, the ultrashort time and length scales associated with the behavior of these highly out-of-equilibrium carriers have impaired experimental verification of ab initio quantum theories. Here, we present an approach to studying plasmonic hot-carrier dynamics that analyzes the temporal waveform of coherent terahertz bursts radiated by photo-ejected hot carriers from designer nano-antennas with a broken symmetry. For ballistic carriers ejected from gold antennas, we find an ~11-femtosecond timescale composed of the plasmon lifetime and ballistic transport time. Polarization- and phase-sensitive detection of terahertz fields further grant direct access to their ballistic transport trajectory. Our approach opens explorations of ultrafast carrier dynamics in optically excited nanostructures.

Tailored Dispersion of Spectro-Temporal Dynamics in Hot-Carrier Plasmonics.

Ultrafast optical switching in plasmonic platforms relies on the third-order Kerr nonlinearity, which is tightly linked to the dynamics of hot carriers in nanostructured metals. Although extensively utilized, a fundamental understanding on the dependence of the switching dynamics upon optical resonances has often been overlooked. Here, all-optical control of resonance bands in a hybrid photonic-plasmonic crystal is employed as an empowering technique for probing the resonance-dependent switching dynamics upon hot carrier formation. Differential optical transmission measurements reveal an enhanced switching performance near the anti-crossing point arising from strong coupling between local and nonlocal resonance modes. Furthermore, entangled with hot-carrier dynamics, the nonlinear correspondence between optical resonances and refractive index change results in tailorable dispersion of recovery speeds which can notably deviate from the characteristic lifetime of hot carriers. The comprehensive understanding provides new protocols for optically characterizing hot-carrier dynamics and optimizing resonance-based all-optical switches for operations across the visible spectrum.

Building Multifunctional Metasystems via Algorithmic Construction.

Flat optics foresees a promising route to ultracompact optical devices, where metasurfaces serve as the foundation. Conventional designs of metasurfaces start with a certain structure as the prototype, followed by extensive parametric sweeps to accommodate the requirements of phase and amplitude of the emerging light. Regardless of how computation consuming the process is, a predefined structure can hardly realize the independent control over polarization, frequency, and spatial channels, which hinders the potential of metasurfaces to be multifunctional. Besides, achieving complicated and multiple functions calls for designing metasystems with multiple cascading layers of metasurfaces, which introduces exponential complexity. In this work, we present a hybrid deep learning framework for designing multilayer metasystems with multifunctional capabilities. We demonstrate examples of a polarization-multiplexed dual-functional beam generator, a second-order differentiator for all-optical computing, and a space-polarization-wavelength multiplexed hologram. These examples are barely achievable by single-layer metasurfaces and unattainable by traditional design processes.

Compounding Meta-Atoms into Metamolecules with Hybrid Artificial Intelligence Techniques.

Molecules composed of atoms exhibit properties not inherent to their constituent atoms. Similarly, metamolecules consisting of multiple meta-atoms possess emerging features that the meta-atoms themselves do not possess. Metasurfaces composed of metamolecules with spatially variant building blocks, such as gradient metasurfaces, are drawing substantial attention due to their unconventional controllability of the amplitude, phase, and frequency of light. However, the intricate mechanisms and the large degrees of freedom of the multielement systems impede an effective strategy for the design and optimization of metamolecules. Here, a hybrid artificial-intelligence-based framework consolidating compositional pattern-producing networks and cooperative coevolution to resolve the inverse design of metamolecules in metasurfaces is proposed. The framework breaks the design of the metamolecules into separate designs of meta-atoms, and independently solves the smaller design tasks of the meta-atoms through deep learning and evolutionary algorithms. The proposed framework is leveraged to design metallic metamolecules for arbitrary manipulation of the polarization and wavefront of light. Moreover, the efficacy and reliability of the design strategy are confirmed through experimental validations. This framework reveals a promising candidate approach to expedite the design of large-scale metasurfaces in a labor-saving, systematic manner.

Trajectory of right ventricular indices is an early predictor of outcomes in hypoplastic left heart syndrome.

BACKGROUND: Children with hypoplastic left heart syndrome (HLHS) have risk for mortality and/or transplantation. Previous studies have associated right ventricular (RV) indices in a single echocardiogram with survival, but none have related serial measurements to outcomes. This study sought to determine whether the trajectory of RV indices in the first year of life was associated with transplant-free survival to stage 3 palliation (S3P). METHODS: HLHS patients at a single center who underwent stage 1 palliation (S1P) between 2000 and 2015 were reviewed. Echocardiographic indices of RV size and function were obtained before and following S1P and stage 2 palliation (S2P). The association between these indices and transplant-free survival to S3P was examined. RESULTS: There were 61 patients enrolled in the study with 51 undergoing S2P, 20 S3P, and 18 awaiting S3P. In the stage 1 perioperative period, indexed RV end-systolic area increased in patients who died or needed transplant following S2P, and changed little in those surviving to S3P (3.37 vs -0.04 cm2 /m2 , P = .017). Increased indexed RV end-systolic area was associated with worse transplant-free survival. (OR = 0.815, P = .042). In the interstage period, indexed RV end-diastolic area increased less in those surviving to S3P (3.6 vs 9.2, P = .03). CONCLUSION: Change in indexed RV end-systolic area through the stage 1 perioperative period was associated with transplant-free survival to S3P. Neither the prestage nor poststage 1 indexed RV end-systolic area was associated with transplant-free survival to S3P. Patients with death or transplant before S3P had a greater increase in indexed RV end-diastolic area during the interstage period. This suggests earlier serial changes in RV size which may provide prognostic information beyond RV indices in a single study.

The nonavalent vaccine: a review of high-risk HPVs and a plea to the CDC.

Two of the leading strategies to prevent cervical cancer are prophylactic human papillomavirus (HPV) vaccination and routine Papanicolaou (Pap) testing. However, regardless of being vaccinated with first-generation (bivalent and quadrivalent) HPV vaccines at the recommended dosing schedule, many women are still found to have low- and high-grade cervical intraepithelial lesions. Studies have shown that this is largely due to: (1) first-generation vaccines only protecting against 70% of high-risk HPV types that cause cervical cancer (HPVs 16/18) and (2) vaccinated women being more prone to infection with non-protected high-risk HPV types than unvaccinated women. Fortunately, the FDA recently approved a nonavalent vaccine that protects against 5 additional high-risk HPV types that cause 20% of cervical cancers (HPVs 31/33/45/52/58), which is the only HPV vaccine currently available in the United States. Although the Advisory Committee on Immunization Practices (ACIP) recommends the nonavalent vaccine in men and women up to the age of 45 years, it does not recommend the nonavalent vaccine in those previously vaccinated with 3 doses of bivalent or quadrivalent vaccine, deeming them "adequately vaccinated". As this population is most at risk, this review serves to provide background and argue for a change in their recommendation.

Plasmacytoma-like Posttransplant Lymphoproliferative Disorder in a Pediatric Heart Transplant Recipient.

Posttransplant lymphoproliferative disorder (PTLD) is a diversely manifesting group of lymphoid or plasmacytic proliferations found in solid organ and bone marrow transplant recipients. PTLD occurs as a result of immunosuppression and is often driven by the Epstein Barr virus. Although most commonly of B-cell origin, similar to B-cell lymphomas, PTLD can rarely present as a plasmacytic process, resembling multiple myeloma. Although more common in adults, 8 cases of plasmacytoma-like PTLD have been reported in pediatric renal and combined small bowel-liver transplant recipients. Here, we present a rare report of a plasmacytoma-like PTLD case in a pediatric heart transplant recipient.

Toward single-molecule optical mapping of the epigenome.

The past decade has seen an explosive growth in the utilization of single-molecule techniques for the study of complex systems. The ability to resolve phenomena otherwise masked by ensemble averaging has made these approaches especially attractive for the study of biological systems, where stochastic events lead to inherent inhomogeneity at the population level. The complex composition of the genome has made it an ideal system to study at the single-molecule level, and methods aimed at resolving genetic information from long, individual, genomic DNA molecules have been in use for the last 30 years. These methods, and particularly optical-based mapping of DNA, have been instrumental in highlighting genomic variation and contributed significantly to the assembly of many genomes including the human genome. Nanotechnology and nanoscopy have been a strong driving force for advancing genomic mapping approaches, allowing both better manipulation of DNA on the nanoscale and enhanced optical resolving power for analysis of genomic information. During the past few years, these developments have been adopted also for epigenetic studies. The common principle for these studies is the use of advanced optical microscopy for the detection of fluorescently labeled epigenetic marks on long, extended DNA molecules. Here we will discuss recent single-molecule studies for the mapping of chromatin composition and epigenetic DNA modifications, such as DNA methylation.

Niacin: the evidence, clinical use, and future directions.

The use of FDA-approved niacin (nicotinic acid or vitamin B3) formulations at therapeutic doses, alone or in combination with statins or other lipid therapies, is safe, improves multiple lipid parameters, and reduces atherosclerosis progression. Niacin is unique as the most potent available lipid therapy to increase high-density lipoprotein (HDL) cholesterol and it significantly reduces lipoprotein(a). Through its action on the GPR109A receptor, niacin may also exert beneficial pleiotropic effects independent of changes in lipid levels, such as improving endothelial function and attenuating vascular inflammation. Studies evaluating the impact of niacin in statin-naïve patients on cardiovascular outcomes, or alone and in combination with statins or other lipid therapies on atherosclerosis progression, have been universally favorable. However, the widespread use of niacin to treat residual lipid abnormalities such as low HDL cholesterol, when used in combination with statins among patients achieving very low (<75 mg/dL) low-density lipoprotein cholesterol levels, is currently not supported by clinical outcome trials.

Atrial Fibrillation and Brugada Syndrome.

Since its first description in 1992, the Brugada syndrome (BrS) has attracted significant attention from the cardiology community because of its association with malignant ventricular arrhythmias and sudden cardiac death. Supraventricular tachyarrhythmias in BrS represent a unique and seemingly higher-risk clinical subgroup of patients with BrS. Atrial fibrillation represents the most common supraventricular arrhythmia in patients with BrS, with average ranges reported in the literature of 20% to 40%. This article summarizes the current literature regarding the patient with BrS with atrial fibrillation and discusses the management of these clinically challenging and potentially higher-risk individuals.

Human glial-restricted progenitor transplantation into cervical spinal cord of the SOD1 mouse model of ALS.

Cellular abnormalities are not limited to motor neurons in amyotrophic lateral sclerosis (ALS). There are numerous observations of astrocyte dysfunction in both humans with ALS and in SOD1(G93A) rodents, a widely studied ALS model. The present study therapeutically targeted astrocyte replacement in this model via transplantation of human Glial-Restricted Progenitors (hGRPs), lineage-restricted progenitors derived from human fetal neural tissue. Our previous findings demonstrated that transplantation of rodent-derived GRPs into cervical spinal cord ventral gray matter (in order to target therapy to diaphragmatic function) resulted in therapeutic efficacy in the SOD1(G93A) rat. Those findings demonstrated the feasibility and efficacy of transplantation-based astrocyte replacement for ALS, and also show that targeted multi-segmental cell delivery to cervical spinal cord is a promising therapeutic strategy, particularly because of its relevance to addressing respiratory compromise associated with ALS. The present study investigated the safety and in vivo survival, distribution, differentiation, and potential efficacy of hGRPs in the SOD1(G93A) mouse. hGRP transplants robustly survived and migrated in both gray and white matter and differentiated into astrocytes in SOD1(G93A) mice spinal cord, despite ongoing disease progression. However, cervical spinal cord transplants did not result in motor neuron protection or any therapeutic benefits on functional outcome measures. This study provides an in vivo characterization of this glial progenitor cell and provides a foundation for understanding their capacity for survival, integration within host tissues, differentiation into glial subtypes, migration, and lack of toxicity or tumor formation.

Reduction in expression of the astrocyte glutamate transporter, GLT1, worsens functional and histological outcomes following traumatic spinal cord injury.

The astrocyte glutamate transporter, GLT1, is responsible for the vast majority of glutamate uptake in the adult central nervous system (CNS), thereby regulating extracellular glutamate homeostasis and preventing excitotoxicity. Glutamate dysregulation plays a central role in outcome following traumatic spinal cord injury (SCI). To determine the role of GLT1 in secondary cell loss following SCI, mice heterozygous for the GLT1 astrocyte glutamate transporter (GLT1+/-) and wild-type mice received thoracic crush SCI. Compared with wild-type controls, GLT1+/- mice had an attenuated recovery in hindlimb motor function, increased lesion size, and decreased tissue sparing. GLT1+/- mice showed a decrease in intraspinal GLT1 protein and functional glutamate uptake compared with wild-type mice, accompanied by increased apoptosis and neuronal loss following crush injury. These results suggest that astrocyte GLT1 plays a role in limiting secondary cell death following SCI, and also show that compromise of key astrocyte functions has significant effects on outcome following traumatic CNS injury. These findings also suggest that increasing intraspinal GLT1 expression may represent a therapeutically relevant target for SCI treatment.

Acinetobacter pneumonia: a review.

Acinetobacter species are becoming a major cause of nosocomial infections, including hospital-acquired and ventilator-associated pneumonia. Acinetobacter species have become increasingly resistant to antibiotics over the past several years and currently present a significant challenge in treating these infections. Physicians now rely on older agents, such as polymyxins (colistin), for treatment. This paper reviews the epidemiology, treatment, and prevention of this emerging pathogen.

Allergic rhinitis in Korean immigrants to the United States.

The prevalence of allergic rhinitis among Korean immigrants to the United States is unknown. However, after arrival in the United States, many develop allergic rhinitis for the first time. This study is undertaken to investigate and establish some contributing environmental factors and the time until onset of allergic rhinitis in Korean immigrants to the United States living in Chicago. Information regarding 246 patients of Korean origin who presented to a Chicago allergy/immunology clinic from 1993 to 1998 were analyzed by retrospective chart review. The diagnosis of allergic rhinitis was established by history, physical examination, and skin testing for immediate hypersensitivity to airborne allergens. The mean residential time in the United States of our patients was 13.5 years (range, 2-38 years). The mean interval from arrival in the United States to onset of symptoms was 8 years (range, 0-24 years) The most commonly identified allergens were ragweed pollen (59%), cat pelt (44%), cocklebur pollen (41%), house-dust mite (35%), and Penicillium (29%). We conclude that the spectrum of responsible allergens in Korean immigrants closely resembles that seen in native citizens of the United States and that environmental factors play an important role in the pathogenesis of allergic rhinitis in this population.