Non-Hermitian Hamiltonians for linear and nonlinear optical response: A model for plexcitons.

In polaritons, the properties of matter are modified by mixing the molecular transitions with light modes inside a cavity. Resultant hybrid light-matter states exhibit energy level shifts, are delocalized over many molecular units, and have a different excited-state potential energy landscape, which leads to modified exciton dynamics. Previously, non-Hermitian Hamiltonians have been derived to describe the excited states of molecules coupled to surface plasmons (i.e., plexcitons), and these operators have been successfully used in the description of linear and third order optical response. In this article, we rigorously derive non-Hermitian Hamiltonians in the response function formalism of nonlinear spectroscopy by means of Feshbach operators and apply them to explore spectroscopic signatures of plexcitons. In particular, we analyze the optical response below and above the exceptional point that arises for matching transition energies for plasmon and molecular components and study their decomposition using double-sided Feynman diagrams. We find a clear distinction between interference and Rabi splitting in linear spectroscopy and a qualitative change in the symmetry of the line shape of the nonlinear signal when crossing the exceptional point. This change corresponds to one in the symmetry of the eigenvalues of the Hamiltonian. Our work presents an approach for simulating the optical response of sublevels within an electronic system and opens new applications of nonlinear spectroscopy to examine the different regimes of the spectrum of non-Hermitian Hamiltonians.

Cortical Subarachnoid Hemorrhage in Behcet's Disease.

OBJECTIVE: Cortical subarachnoid hemorrhage (cSAH) can be resulted from by a wide variety of causes. A cSAH probably associated with Behcet's disease is herein reported for the first time. CASE REPORT: A 58-year-old male with stable Behcet's disease evaluated for sudden onset headache. Emergency computed tomography disclosed cSAH in the left frontal sulci. A ruptured middle cerebral artery cortical branch aneurysm was found. Surprisingly, this aneurysm obliterated completely after diagnostic catheter angiography. CONCLUSION: This case highlights three important points; First, non-mycotic (non-infectious) distal cerebral artery aneurysms may rarely cause cSAH. Second, distal dissecting aneurysms may rarely become obliterated after diagnostic cerebral angiography. Third, such aneurysms may be one of the long-term consequences of vascular inflammation in Behçet's disease.

Dual ophthalmic arteries: a new case.

We report one retinoblastoma patient with dual ophthalmic arteries (also known as "double ophthalmic arteries") arising from the internal carotid artery which fuse with each other inside the orbit. The caudal ophthalmic artery with larger caliber originated from the cavernous segment of internal carotid artery and passed through the superior orbital fissure. The cranial and tiny one arose more cranially from the supraclinoid internal carotid artery and passed through the optic canal. After superselective catheterization, frank anastomosis was shown between two ophthalmic arteries and the central retinal artery arose from the cranial one. To the best of our knowledge, this case is the first observation of a dual ophthalmic artery with cavernous/supracavernous origins fusing with each other proven by superselective ophthalmic angiography. Whether there is an anastomosis between two ophthalmic arteries is important for deciding which artery to be selected for intraarterial treatment. In cases of retinoblastoma, detailed angiographic analysis may be essential to examine the orbital arterial system and to avoid unexpected complications during intraarterial chemotherapy.

Stroke Mechanism in COVID-19 Infection: A Prospective Case-Control Study.

BACKGROUND: The characteristics and pathophysiological mechanisms involved in acute ischemic stroke in patients with COVID-19 infection have not been fully clarified. We prospectively studied the phenotypic and etiological features of acute stroke occurring in COVID-19 infection. PATIENTS & METHODS: Within nine months starting from April-2020, the presence of COVID-19 infection was determined by thoracic CT and SARS-CoV-2 PCR in all acute stroke cases managed in a single tertiary center. Consecutive and prospective data on vascular risk factors/comorbidities, in-hospital quality metrics, discharge outcomes, etiological subclassification and blood markers of thrombosis / inflammation were compared in 44 COVID-19 positive cases (37 acute ischemic stroke, 5 TIA, 2 intracerebral hematoma) and 509 COVID-19 negative patients (355 ischemic, 105 TIA, 44 hematoma and 5 stroke mimic). RESULTS: COVID-19 positive patients had more severe strokes, delayed hospital admission, longer hospital stay, higher mortality rates, but had similar vascular risk factors/comorbidities frequency, thrombolysis/thrombectomy utilization rates, metrics, and stroke etiological subtype. They had significantly higher CRP, fibrinogen, ferritin, leukocyte count and lower lymphocyte count. No difference was detected in aPTT, INR, D-dimer, platelet, hemoglobin, homocysteine levels and ANA, anti-dsDNA antibody and ENA panel positivity rates. Anti-phospholipid antibodies have been studied in 70% of COVID-19 positive and all cryptogenic patients, but were never found positive. Tests for coagulation factor levels and hereditary thrombophilia did not show major thrombophilia in any of the stroke patients with COVID-19. CONCLUSION: We documented that there is no significant difference in etiological spectrum in acute stroke patients with COVID-19 infection. In addition, cryptogenic stroke and antiphospholipid antibody positivity rates did not increase.

Large Rabi splitting of mixed plasmon-exciton states in small plasmonic moiré cavities.

We report on exciton-plasmon coupling in metallic moiré cavities, both numerically and experimentally. Moiré cavities fabricated using double exposure laser interference lithography were filled with a molecular dye, J-aggregate. Polarization-dependent spectroscopic reflection measurements supported by simulations reveal strong coupling of organic dye excitons with cavity modes of the plasmonic moiré cavities. An anti-crossing at zero detuning, a clear indication of strong coupling, has been observed when the excitonic absorption band resonates with the cavity mode. Large Rabi splitting energies owing to the strong coupling of plasmons and excitons are clearly observed.

Phosphor-based white LED by various glassy particles: control over luminous efficiency.

Generating white light through a mainstream remote phosphor design suffers from phosphor conversion efficiency loss due to a backscattering of light. Such a loss also reduces luminous efficiency of the resulting white light. To overcome this issue, various glassy scatterers with different morphologies such as glass bubbles, glass beads, and nanosized silica particles were employed as scatterers, together with a fixed amount of yellow phosphor (YAG:Ce3+) and a poly(dimethylsiloxane) (PDMS) matrix. In addition, the simulation of the system validates the rigorous multiple scattering of the incoming light most probably due to refractive index mismatch between the glass bubbles and surrounding PDMS matrix along with the internal reflections.

Graphene-Based Adaptive Thermal Camouflage.

In nature, adaptive coloration has been effectively utilized for concealment and signaling. Various biological mechanisms have evolved to tune the reflectivity for visible and ultraviolet light. These examples inspire many artificial systems for mimicking adaptive coloration to match the visual appearance to their surroundings. Thermal camouflage, however, has been an outstanding challenge which requires an ability to control the emitted thermal radiation from the surface. Here we report a new class of active thermal surfaces capable of efficient real-time electrical-control of thermal emission over the full infrared (IR) spectrum without changing the temperature of the surface. Our approach relies on electro-modulation of IR absorptivity and emissivity of multilayer graphene via reversible intercalation of nonvolatile ionic liquids. The demonstrated devices are light (30 g/m2), thin (<50 µm), and ultraflexible, which can conformably coat their environment. In addition, by combining active thermal surfaces with a feedback mechanism, we demonstrate realization of an adaptive thermal camouflage system which can reconfigure its thermal appearance and blend itself with the varying thermal background in a few seconds. Furthermore, we show that these devices can disguise hot objects as cold and cold ones as hot in a thermal imaging system. We anticipate that, the electrical control of thermal radiation would impact on a variety of new technologies ranging from adaptive IR optics to heat management for outer space applications.

Floating Aortic Thrombus: A Rare Cause of Acute Ischemic Stroke Necessitating Modification of Access Route for Thrombectomy.

We report 2 patients with acute occlusion of middle cerebral artery successfully treated by mechanical thrombectomy performed via transbrachial access. Both patients had floating aortic arch thrombi precluding safe transfemoral access due to risk of further iatrogenic embolization. Moreover both patients were diagnosed with hypercoagulopathy secondary to lung malignancy (paraneoplastic etiology, Trousseau's syndrome) as the cause of both aortic thrombi and acute ischemic stroke. Mechanical thrombectomy in the setting of a floating aortic thrombus has been mentioned only once as part of general management of floating aortic thrombi in the whole body. To the best of our knowledge, it has never been described previously in the literature in the context of cerebral mechanical thrombectomy technique. However, the diagnosis of this entity bears clinical importance for it can modify the treatment approach. A modified transbrachial approach allowed us to treat both patients without neurologic complications and resulted in modified Rankin scores of 1 on follow-up. We advise that the cross-sectional imaging of acute stroke patients should include an evaluation of the aortic arch and should be scrutinized in detail especially in patients with possible hypercoagulable state. Flat panel computed tomography technology allowed us to obtain such an imaging study in the angiography suite.

Observation of Mode Splitting in Photoluminescence of Individual Plasmonic Nanoparticles Strongly Coupled to Molecular Excitons.

Plasmon-exciton interactions are important for many prominent spectroscopic applications such as surface-enhanced Raman scattering, plasmon-mediated fluorescence, nanoscale lasing, and strong coupling. The case of strong coupling is analogous to quantum optical effects studied in solid state and atomic systems previously. In plasmonics, similar observations have been almost exclusively made in elastic scattering experiments; however, the interpretation of these experiments is often cumbersome. Here, we demonstrate mode splitting not only in scattering, but also in photoluminescence of individual hybrid nanosystems, which manifests a direct proof of strong coupling in plasmon-exciton nanoparticles. We achieved these results due to saturation of the mode volume with molecular J-aggregates, which resulted in splitting up to 400 meV, that is, ∼20% of the resonance energy. We analyzed the correlation between scattering and photoluminescence and found that splitting in photoluminescence is considerably less than that in scattering. Moreover, we found that splitting in both photoluminescence and scattering signals increased upon cooling to cryogenic temperatures. These findings improve our understanding of strong coupling phenomena in plasmonics.

Nonthrombotic Pulmonary Artery Embolism: Imaging Findings and Review of the Literature.

OBJECTIVE: The purpose of this article is to emphasize the imaging findings encountered in the setting of nonthrombotic pulmonary embolism. CONCLUSION: Nonthrombotic pulmonary embolism refers to a spectrum of clinical and radiologic disorders caused by embolization of the pulmonary artery vasculature by various cell types, microorganism, and foreign bodies. Awareness of the imaging and clinical features of the nonthrombotic pulmonary embolism may facilitate prompt diagnosis.

Dynamic tuning of plasmon resonance in the visible using graphene.

We report active electrical tuning of plasmon resonance of silver nanoprisms (Ag NPs) in the visible spectrum. Ag NPs are placed in close proximity to graphene which leads to additional tunable loss for the plasmon resonance. The ionic gating of graphene modifies its Fermi level from 0.2 to 1 eV, which then affects the absorption of graphene due to Pauli blocking. Plasmon resonance frequency and linewidth of Ag NPs can be reversibly shifted by 20 and 35 meV, respectively. The coupled graphene-Ag NPs system can be classically described by a damped harmonic oscillator model. Atomic layer deposition allows for controlling the graphene-Ag NP separation with atomic-level precision to optimize coupling between them.

Ultra hybrid plasmonics: strong coupling of plexcitons with plasmon polaritons.

We report a ternary-coupled plasmonic system consisting of excitons of J-aggregated dye, localized surface plasmon polaritons of Ag nanoparticles, and propagating surface plasmon polaritons of continuous Ag film. J-aggregate dyes are uniformly self-assembled on colloidally synthesized Ag nanoprisms forming plexcitonic nanoparticles, which are placed at a distance nanometers away from the Ag thin film. The reflection measurements, corroborated by theoretical predictions, reveal that the strong coupling of plasmon polaritons and plexcitons results in a newly formed plasmon-exciton-plasmon hybridized state that we call here, reportedly for the first time, a plexcimon state. The hybrid plasmonic system shows dispersion characteristics similar to a coupled resonator optical waveguide. The group velocity of the plexcimon state approaches zero at the band edges. The ultrahybrid plasmonic system presented here is promising for a variety of light-matter interaction studies, including polariton lasers, plasmonic devices, plasmonic waveguiding, and spectroscopy.

Strong coupling between localized and propagating plasmon polaritons.

We investigate plasmon-plasmon (PP) coupling in the strongly interacting regimes by using a tunable plasmonic platform consisting of triangular Ag nanoprisms placed nanometers away from Ag thin films. The nanoprisms are colloidally synthesized using a seed-mediated growth method and having size-tunable localized surface plasmon polariton (SPP) resonances immobilized on Si(3)N(4) films. The PP coupling between the localized SPPs of metal nanoprisms and the propagating SPPs of the metal film is controlled by the nanoprism concentration and the plasmon damping in the metal film. Results reveal that Rabi splitting energy determining the strength of the coupling can reach up to several hundreds meV, thus demonstrating the ultrastrong coupling occurring between localized and propagating SPPs. The metal nanoparticle-metal thin film hybrid system over the square-centimeter areas presented here provides a unique configuration to study PP coupling all the way from the weak to ultrastrong coupling regimes in a broad range of wavelengths.

Plexcitonic crystals: a tunable platform for light-matter interactions.

Coupled states of surface plasmon polaritons (SPPs) and excitons are collectively called plexcitons [Nano Lett.8, 3481 (2008)]. Plexcitonics is an emerging field of research aiming to control light-matter interaction at the nanometer length scale using coupled pairs of surface-plasmons and excitons. Ability to control the interaction between localized excitons and propagating surface-plasmons is important for realization of new photonic devices. In this letter, we report plexcitonic crystals that yield direction-dependent plasmon-exciton coupling. We have fabricated one- and two-dimensional plexcitonic crystals on periodically corrugated silver surfaces, which are loaded with J-aggregate complexes. We show that plasmon-exciton coupling is blocked for some crystal directions when exciton energy falls inside the plasmonic band gap of the periodically corrugated metallic surface.

Plasmonic band gap engineering of plasmon-exciton coupling.

Controlling plasmon-exciton coupling through band gap engineering of plasmonic crystals is demonstrated in the Kretschmann configuration. When the flat metal surface is textured with a sinusoidal grating only in one direction, using laser interference lithography, it exhibits a plasmonic band gap because of the Bragg scattering of surface plasmon polaritons on the plasmonic crystals. The contrast of the grating profile determines the observed width of the plasmonic band gap and hence allows engineering of the plasmonic band gap. In this work, resonant coupling between the molecular resonance of a J-aggregate dye and the plasmonic resonance of a textured metal film is extensively studied through plasmonic band gap engineering. Polarization dependent spectroscopic reflection measurements probe the spectral overlap occurring between the molecular resonance and the plasmonic resonance. The results indicate that plasmon-exciton interaction is attenuated in the band gap region along the grating direction.

Absorption enhancement of molecules in the weak plasmon-exciton coupling regime.

We report on the experimental and theoretical investigations of enhancing the optical absorption of organic molecules in the weak plasmon-exciton coupling regime. A metal-organic hybrid structure consisting of dye molecules embedded in the polymer matrix is placed in close vicinity to thin metal films. We have observed a transition from a weak coupling regime to a strong coupling one as the thickness of the metal layer increases. The results indicate that absorption of the self-assembled J-aggregate nanostructures can be increased in the weak plasmon-exciton coupling regime and strongly quenched in the strong coupling regime. A theoretical model based on the transfer-matrix method qualitatively confirms the experimental results obtained from polarization-dependent spectroscopic reflection measurements.

Initial Experience with the Derivo 2Heal Flow Diverter under Standard or Reduced-Dose Single Antiplatelet Therapy.

BACKGROUND AND PURPOSE: Flow diverters with surface modifications or coatings have been recently introduced to clinical practice with the expectation that they can reduce the rate of thromboembolic complications and residual aneurysms. The purpose of this study is to evaluate the utility of the Derivo 2Heal (D2H) device, a new fibrin and heparin-coated flow diverter. MATERIALS AND METHODS: Patients treated by a single operator by using the D2H were retrospectively evaluated for demographic data, aneurysm characteristics, procedural variables, and follow-up data. All patients were treated by using a single D2H, monitored by platelet function testing and kept under single antiplatelet therapy with regular or half-dose clopidogrel or prasugrel after the procedure. RESULTS: Twenty patients with 26 aneurysms were treated. Three presented acutely with subarachnoid hemorrhage. Adjunctive devices were used in 6 patients. There were no technical failures and 2 periprocedural self-limited nonthrombotic minor adverse events. During follow-up, 1 of the acutely ruptured aneurysms reruptured, and 1 patient had a visual TIA. All patients were doing well clinically (19 with mRS of 0 and 1 with 1) at the last follow-up after discharge. The rates of total occlusion on very early angiographic (MRA/CTA or DSA, mean: 2.4 months), DSA (mean: 5.8 months), and midterm angiographic (mean: 14.5 months) follow-up for all versus uncoiled aneurysms were 68% versus 70%, 77.8% versus 90.0%, and 91.7% versus 90.1%, respectively. CONCLUSIONS: The absence of permanent neurologic deficits in the periprocedural period and favorable occlusion rates in this preliminary study suggest that the novel coating comprising fibrin and heparin may have the potential to increase the safety and efficacy of flow diversion and needs to be further studied by comparing the D2H device with its bare counterpart and other coated or surface-modified flow diverters.

Use of a new low-profile coronary stent graft for the treatment of intracranial carotid blow-out.

A 50-year-old male patient with a history of transcranial surgery and subsequent radiotherapy for a pituitary adenoma presented with repetitive pulsatile nasal bleeding. A right cavernous segment pseudoaneurysm was discovered on the angiogram, and the patient failed the balloon occlusion test. A Papyrus (Biotronik, Berlin, Germany) stent graft, which is approved for coronary interventions, was successfully deployed over a coaxial guiding system during the emergent treatment of the false aneurysm. The patient tolerated the procedure well and nasal bleeding did not recur after the procedure. At one-year angiographic follow-up, the stent graft was patent and there was no evidence of recanalization of the false aneurysm.

Correlation Between Quantitative Parameters Obtained by Dual Energy Spectral CT and Prognostic Histopathological Factors and Biomarkers in Breast Cancer.

RATIONALE AND OBJECTIVES: To investigate the correlation between quantitative parameters obtained by dual energy spectral computed tomography (DESCT) and various histopathological factors and biomarkers associated with the prognosis of breast cancer. MATERIALS AND METHODS: Quantitative parameters such as iodine content (IC), normalized IC (nIC), iodine enhancement (IE) and normalized IE (nIE) were measured on virtual monochromatic images and iodine mapping images obtained from DESCT in 116 female breast cancer patients. The relationship between these parameters and prognostic biomarkers such as estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) status and Ki67 levels, as well as the correlation with histological grade (HG), lymphovascular invasion (LVI), and metastatic axillary lymphadenopathy (LAP) were evaluated. RESULTS: ER-negative tumors had significantly higher values of IC, nIC, IE, and nIE compared to ER-positive tumors. PR-negative tumors had significantly higher values of IE and nIEc compared to PR-positive tumors. HER2 overexpressed and Ki-67 high proliferation tumors showed significantly higher values of all quantitative parameters compared to HER2 negative and Ki-67 low proliferation tumors. All quantitative parameters were significantly higher in HG 3 tumors, tumors with detected LVI, and tumors with metastatic axillary LAP compared to low-grade tumors, LVI-negative tumors and tumors without metastatic axillary lymph nodes, respectively. CONCLUSION: Quantitative parameters of IC and IE obtained from DESCT have shown potential for predicting prognosis in breast cancer patients. Higher values of these parameters have been found to correlate with poor prognostic biomarkers and histopathological features. These results suggest that quantitative DESCT imaging may offer an additional benefit in the noninvasive prediction of breast cancer prognosis.

Non-routine thrombectomy in pediatric arterial ischemic stroke.

PURPOSE: Unlike in adults, the indications and techniques for mechanical thrombectomy for arterial ischemic stroke (AIS) in children are not clearly established. The medical and interventional management of children with acute large vessel occlusion may entail the modification of the standardized management of this condition in adults. We present six cases of children who underwent non-routine thrombectomy for AIS. METHODS: We retrospectively reviewed the records of children diagnosed with AIS between 2015 and 2023 and evaluated patient characteristics, procedural technical data, and final clinical outcomes. Procedures deviating from the current definition and indications for AIS treatment in adults as well as previously reported pediatric thrombectomy cases were defined as non-routine thrombectomy. RESULTS: Seven non-routine thrombectomy procedures in six children were included in the study. The National Institutes of Health Stroke Scale scores on admission ranged from 4 to 35; no procedure-related mortality or major neurologic morbidity occurred. One child died of causes related to the initial severe heart failure and stroke; otherwise, all the children had a modified Rankin scale score of 0 to 1 at follow-up. Unique clinical and procedural features in our case series included presentation with acute stent occlusion (two children), bilateral simultaneous internal carotid artery occlusions associated with a unilateral tandem middle cerebral artery (MCA) occlusion (one child), MCA occlusion caused by thromboembolism of the atrial myxoma (one child), and very distal (one child) or delayed thrombectomy (two children). CONCLUSION: Modifications to the standard medical and interventional algorithms may be required for mechanical thrombectomy in children. CLINICAL SIGNIFICANCE: Referral centers specialized in pediatric neurology, pediatric anesthesia, and pediatric intervention are optimal for treating children using mechanical thrombectomy and for modifying the treatment, if required.