Publications by authors named "Sinan Balci"

36 Publications

Dual Stenting with New Generation Stents for Aneurysm Embolization in Acute Subarachnoid Hemorrhage.

World Neurosurg 2021 Jul 3. Epub 2021 Jul 3.

Ankara Hacettepe University, Department of Interventional Radiology Ankara, Turkey. Electronic address:

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http://dx.doi.org/10.1016/j.wneu.2021.06.135DOI Listing
July 2021

Multispectral Graphene-Based Electro-Optical Surfaces with Reversible Tunability from Visible to Microwave Wavelengths.

Nat Photonics 2021 Jul 5;15(7):493-498. Epub 2021 Apr 5.

Department of Materials, University of Manchester, Manchester, M13 9PL, UK.

Optical materials with colour-changing abilities have been explored for display devices, smart windows, or modulation of visual appearance. The efficiency of these materials, however, has strong wavelength dependence, which limits their functionality to a specific spectral range. Here, we report graphene-based electro-optical devices with unprecedented optical tunability covering the entire electromagnetic spectrum from the visible to microwave. We achieve this non-volatile and reversible tunability by electro-intercalation of lithium into graphene layers in an optically accessible device structure. This unique colour-changing capability, together with area-selective intercalation, inspires fabrication of new multispectral devices, including display devices and electro-optical camouflage coating. We anticipate that these results provide realistic approaches for programmable smart optical surfaces with a potential utility in many scientific and engineering fields such as active plasmonics and adaptive thermal management.
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http://dx.doi.org/10.1038/s41566-021-00791-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7611111PMC
July 2021

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

J Stroke Cerebrovasc Dis 2021 Aug 1;30(8):105919. Epub 2021 Jun 1.

Department of Neurology, Hacettepe University Hospitals Turkey.

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.
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http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2021.105919DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8166511PMC
August 2021

The implications of magnetic resonance angiography artifacts caused by different types of intracranial flow diverters.

J Cardiovasc Magn Reson 2021 Jun 7;23(1):69. Epub 2021 Jun 7.

Department of Radiology, Hacettepe University Hospitals, Ankara, Turkey.

Background: Serial cerebral angiographic imaging is necessary to ensure cerebral aneurysm occlusion after flow diverter placement. Time-of-flight (TOF)-magnetic resonance angiography (MRA) is used for this purpose due to its lack of radiation, contrast media and complications. The comparative diagnostic yield of TOF-MRA for different flow diverters has not been previously analyzed.

Purpose: To evaluate the diagnostic accuracy of TOF-MRA in cerebral aneurysms treated w divertersith different flow diverters.

Materials And Methods: Flow-diverted patients whose cerebral follow-up MRA and digital subtraction angiograms (DSA) were obtained within 6 weeks were retrospectively identified. The DSA (as gold standard) and MRA images of these patients were compared by two readers (blinded to both patient data and endovascular procedure data) for residual aneurysms and the status of the parent artery for each type of flow diverter. In a second group of patients, magnetic susceptibility artifacts were manually measured and compared for different FDs.

Results: Seventy-six patients (85 aneurysms) were included in group one, and 86 patients (95 aneurysms) were included in group 2. TOF-MRA and DSA showed almost perfect agreement for residual aneurysms (κ = 0.88, p < 0.001) (positive predictive value (PPV) = 1.00, specificity = 1.00, negative predictive value (NPV) = 0.89, sensitivity = 0.89). Intermodality agreement (κ = 0.97 vs. κ = 0.74, p < 0.005) and sensitivity (0.97 vs. 0.77, NPV: 0.96 vs. 0.77) were highest with nitinol stents. MRA and DSA showed no agreement for occluded or stenotic parent vessels (κ = 0.13, p = 0.015, specificity = 0.44, NPV = 1.00, sensitivity = 1.00). Specificity was lower in chromium-cobalt based FDs than in nitinol devices (specificity = 0.08 vs. 0.60). Chromium-cobalt stents generated the largest artifacts (p < 0.005). The size of the device-related artifact, in millimeters, increased in respective order, for the Silk, Derivo, Pipeline and Surpass devices.

Conclusion: Unlike DSA, TOF-MRA is susceptible to dissimilarities between flow diverters. MRA is not well-suited for research studies comparing different flow diverters. Nitinol FDs appear to be advantageous for TOF-MRA follow-up so as not to miss small aneurysm remnants or clinically relevant parent artery stenosis.
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http://dx.doi.org/10.1186/s12968-021-00753-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8182930PMC
June 2021

Dual Testing to Achieve Low On-treatment Platelet Reactivity for Aneurysm Embolization.

Clin Neuroradiol 2021 Apr 12. Epub 2021 Apr 12.

Department of Radiology, Hacettepe University Hospitals, Ankara, Turkey.

Background And Purpose: Although point-of-care tests are used extensively to test platelet function before endovascular aneurysm treatment, their use and validity are still debated. We compared the results of two point-of-care tests (VerifyNow® and Multiplate®) for assessing patients treated with stents and flow diverters and determined their relation to periprocedural complications.

Methods: All patients undergoing treatment of intracranial aneurysms were tested using both methods and were retrospectively evaluated. Patients with acute subarachnoid hemorrhage and those who had to be maintained on anticoagulants for unrelated diseases were excluded. An acceptable level of platelet inhibition was required on both tests to commence with treatment, otherwise antiplatelet medication was adjusted to reach this level.

Results: Mean PRU (platelet reactivity units) and ADP AUC (adenosine diphosphate area under the aggregation curve) were 68 ± 66 and 23 ± 15, respectively, in 295 patients. Both tests showed a good correlation (r = 0.45). Both tests were able to predict hemorrhagic events but not ischemic events. When patients with very low reactivity (PRU < 60) were compared to the rest of the group, there were more hemorrhagic events in the first group but the overall rate of complications were similar (p = 0.27).

Conclusion: In this largest study comparing two widely used commercial platelet function tests, the correlation between the tests were less than ideal; however, the very low platelet reactivity attained by the help of dual platelet testing did not result in an increased overall complication rate.
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http://dx.doi.org/10.1007/s00062-021-01011-7DOI Listing
April 2021

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

Opt Lett 2020 Oct;45(20):5824-5827

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.
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http://dx.doi.org/10.1364/OL.405278DOI Listing
October 2020

Validity of US measurements of cam-type femoroacetabular impingement parameters: a preliminary study in an asymptomatic adult population.

Jpn J Radiol 2020 Nov 19;38(11):1082-1089. Epub 2020 Jun 19.

Department of Radiology, Faculty of Medicine, Hacettepe University, Sıhhiye, 06100, Ankara, Turkey.

Purpose: To determine the accuracy of US for the quantitative parameters of cam-type femoroacetabular impingement (FAI) in an asymptomatic adult population, using MRI as the reference standard.

Materials And Methods: We prospectively evaluated 158 hips of 79 adult subjects (44 males, 35 females; age range 18-49 years) with a negative anterior impingement test. Two observers independently measured anterosuperior quadrant alpha angles and anterior femoral distances (AFDs) on both US and MRI.

Results: US measurements of alpha angle and AFD had a moderate-to-high positive correlation with MRI measurements and there was substantial and/or almost perfect agreement between observers on both imaging modalities. Anterior femoral distance measurements for both observers and alpha angles at MRI for Observer 1 showed no statistically significant difference between genders.

Conclusion: Ultrasonography can be used for anterosuperior alpha angle and AFD measurements in asymptomatic adults. However, when used as the sole imaging method, its inherent limitations and possible discrepancies with MRI should be kept in mind.
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http://dx.doi.org/10.1007/s11604-020-01005-4DOI Listing
November 2020

Percutaneous drainage of retroperitoneal abscesses: variables for success, failure, and recurrence.

Diagn Interv Radiol 2020 Mar;26(2):124-130

Department of Radiology, Hacettepe University School of Medicine, Ankara, Turkey.

Purpose: We aimed to evaluate the success and failure rates and minor and major complications of percutaneous drainage of retroperitoneal abscesses.

Methods: Between 1990 and 2010, percutaneously drained 170 retroperitoneal abscesses in 150 patients (83 males, 67 females, median age 44.2 years, age range, 1-86 years) were included retrospectively. Percutaneous drainage of retroperitoneal abscesses was performed under the guidance of ultrasonography and fluoroscopy or computed tomography. Six abscesses were drained via single needle aspiration whereas 164 abscesses were drained via catheters of 6-14 F calibre using the Seldinger technique.

Results: When all retroperitoneal abscesses are considered, success rates were found as follows: 75.3% cure (128/170), 7.7% temporization (13/170), 4.1% palliation (7/170). Failure rate was 12.9% (22/170). Recurrence rate was 10.6% (18/170), and 13 of the recurred abscesses were treated via second session percutaneous drainage. Mortality rate was 2.7% (4/150).

Conclusion: Percutaneous drainage is the first treatment option for retroperitoneal abscesses due to procedural reliability, elimination of need for general anesthesia, better tolerability, and lower morbidity and mortality rates compared with the surgical methods. High cure, temporization, or palliation rates can be obtained via imaging-guided percutaneous drainage for all retroperitoneal abscesses with a safe access route.
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http://dx.doi.org/10.5152/dir.2019.19199DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7051265PMC
March 2020

Y-Stent-Assisted Coiling With Low-Profile Neuroform Atlas Stents for Endovascular Treatment of Wide-Necked Complex Intracranial Bifurcation Aneurysms.

Neurosurgery 2020 09;87(4):744-753

Department of Radiology, Hacettepe University Hospital, Ankara, Turkey.

Background: Y-stent-assisted coiling is one of the eligible techniques for the treatment of complex bifurcation aneurysms. In majority of previous literature, Y-stenting has been performed using stents that could be delivered through large profile microcatheters that are often difficult to manipulate during navigation through sharply angled side branches. Attempts to navigate with these large profile catheters might cause serious complications during Y-stenting procedure.

Objective: To investigate the safety, feasibility, and efficacy of Y-stent-assisted coiling procedure with Neuroform Atlas stents for the treatment of complex bifurcation aneurysms; Neuroform Atlas is a recently introduced open-cell stent that can be delivered though low-profile microcatheters.

Methods: We identified the patients with intracranial bifurcation aneurysms treated by Y-stent-assisted coiling procedure with Neuroform Atlas stents. We assessed the immediate postoperative and follow-up clinical and angiographic outcomes. We also investigated the periprocedural and delayed complications.

Results: A total of 30 aneurysms in 30 patients were included in the study. Y-stenting was successfully performed without any technical complications in all cases (100%). Immediate postprocedural angiography revealed total aneurysm occlusion in 83.3% of patients. The mean angiographic follow-up time was 11.8 mo. The last follow-ups showed complete occlusion in 93.3% of patients. There was no mortality in this study. A procedure-related complication developed in 6.7% and resulted in permanent morbidity in 3.3% of patients.

Conclusion: Neuroform Atlas stent combines the advantages of low-profile deployment microcatheters with an open-cell structure to achieve a successful Y-stenting procedure. Y-stent-assisted coiling with Neuroform Atlas stents provides a safe and effective endovascular treatment for wide-necked complex bifurcation aneurysms.
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http://dx.doi.org/10.1093/neuros/nyz516DOI Listing
September 2020

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

J Stroke Cerebrovasc Dis 2019 Nov 21;28(11):104291. Epub 2019 Aug 21.

Department of Radiology, Hacettepe University Faculty of Medicine, Ankara, Turkey. Electronic address:

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.
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http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2019.07.007DOI Listing
November 2019

Unusual ophthalmic artery origin: Implications for intraarterial chemotherapy of retinoblastoma.

Interv Neuroradiol 2019 Dec 3;25(6):638-643. Epub 2019 Jun 3.

Department of Radiology, Hacettepe University Faculty of Medicine, Sıhhiye, Ankara, Turkey.

We report two pediatric retinoblastoma patients with unusual ophthalmic artery (OA) origins who were referred to our interventional neuroradiology department for intraarterial chemotherapy. The first patient had double OAs arising from the ipsilateral internal carotid artery and a central retinal artery (CRA) arising from the more cranially located artery, whereas the second patient had an OA originating from the A1 segment of the ipsilateral anterior cerebral artery. In both cases the CRA arose from the artery entering the orbit through the optic foramen. Both patients tolerated the procedures well. To the best of our knowledge, our retinoblastoma patients with unusual OA origins are the first in the literature in which detailed knowledge of the orbital vasculature and especially CRA origin carried immediate clinical implications, altering access strategies. These variations were proved both by flat-panel detector computed tomography findings and superselective injections of OAs with unusual origins. Our results show that in patients with retinoblastoma, a detailed angiographic work-up may be necessary to evaluate the orbital vasculature and possible abnormal origin of the OA. Recognition of possible variations of OA origin and its branching patterns is of the utmost importance for successful treatment and avoidance of adverse events among retinoblastoma patients.
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http://dx.doi.org/10.1177/1591019919852737DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6838853PMC
December 2019

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

Opt Lett 2019 Feb;44(3):479-482

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:Ce) 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.
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http://dx.doi.org/10.1364/OL.44.000479DOI Listing
February 2019

MRI evaluation of anal and perianal diseases.

Diagn Interv Radiol 2019 Jan;25(1):21-27

Department of Radiology, Hacettepe University School of Medicine, Ankara, Turkey.

Anal and perianal region is a commonly affected area in the course of several inflammatory, infectious, and neoplastic diseases. Several imaging modalities may be used in imaging evaluation of this area and magnetic resonance imaging (MRI) emerges as the imaging modality of choice due to its superb soft tissue resolution. MRI is not only useful for initial detection of anal/perianal pathologies but also in the follow-up of these disorders. In this article, we aimed to illustrate MRI findings of several diseases affecting this area including perianal fistula as well as anal fissure, hypertrophic myopathy of internal anal sphincter, hidradenitis suppurativa, pilonidal sinus, rectovaginal/anovaginal fistula and anal canal carcinoma. We think that this article will serve to familiarize the imaging specialists to the MRI findings of these diseases.
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http://dx.doi.org/10.5152/dir.2018.17499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339630PMC
January 2019

Usefulness of contrast-enhanced and TOF MR angiography for follow-up after low-profile stent-assisted coil embolization of intracranial aneurysms.

Interv Neuroradiol 2018 Dec 5;24(6):655-661. Epub 2018 Jul 5.

4 Department of Radiology, Artvin State Hospital, Artvin, Turkey.

Background: Low-profile, self-expandable stents are used to treat wide-neck aneurysms located on the smaller distal intracranial arteries. This study aimed to assess the usefulness of time-of-flight (TOF) and contrast-enhanced (CE) magnetic resonance angiography (MRA) for follow-up after LEO Baby stent (LBS)-assisted coil embolization.

Methods: Twenty-four aneurysms treated with LBS-assisted coil embolization were evaluated. Researchers reviewed TOF MRA and CE MRA images in terms of occlusion and stent patency. Aneurysm occlusion was graded according to Raymond-Roy classification as follows: total occlusion (grade 1), residual neck (grade 2), and residual aneurysm (grade 3). Stent patency was scored as follows: occlusion (1), stenosis (2), and normal (3). Interobserver and intermodality agreement values were determined by weighted kappa (κ) statistics.

Results: Intermodality and interobserver values of TOF MRA and CE MRA with digital subtraction angiography (DSA) were perfect (κ = 1.00, p < 0.001) in terms of aneurysm occlusion. Rate of stent occlusion and stenosis in DSA, TOF, and MRA, respectively, were as follows: 0 and 12.5%, 16.6 and 70.8%, and 0 and 62.5%. Intermodality agreement values of TOF MRA and CE MRA with DSA were insignificant in terms of stent patency (κ = 0.065, p = 0.27; κ = 0.158, p = 0.15, respectively). Interobserver agreement was substantial in both TOF MRA (κ = 0.71, p < 0.001) and CE MRA (κ = 0.64, p = 0.001).

Conclusions: Both TOF and CE MRA techniques have strong concordance with DSA for the detection of aneurysm occlusion status. CE MRA can be used as a first-line noninvasive imaging modality due to its superiority to TOF MRA with respect to the visualization of in-stent signals.
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http://dx.doi.org/10.1177/1591019918785910DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6259350PMC
December 2018

Graphene-Based Adaptive Thermal Camouflage.

Nano Lett 2018 07 27;18(7):4541-4548. Epub 2018 Jun 27.

Department of Physics , Bilkent University , 06800 , Ankara Turkey.

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/m), 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.
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http://dx.doi.org/10.1021/acs.nanolett.8b01746DOI Listing
July 2018

Electrically switchable metadevices via graphene.

Sci Adv 2018 01 5;4(1):eaao1749. Epub 2018 Jan 5.

Department of Physics, Bilkent University, 06800 Ankara, Turkey.

Metamaterials bring subwavelength resonating structures together to overcome the limitations of conventional materials. The realization of active metadevices has been an outstanding challenge that requires electrically reconfigurable components operating over a broad spectrum with a wide dynamic range. However, the existing capability of metamaterials is not sufficient to realize this goal. By integrating passive metamaterials with active graphene devices, we demonstrate a new class of electrically controlled active metadevices working in microwave frequencies. The fabricated active metadevices enable efficient control of both amplitude (>50 dB) and phase (>90°) of electromagnetic waves. In this hybrid system, graphene operates as a tunable Drude metal that controls the radiation of the passive metamaterials. Furthermore, by integrating individually addressable arrays of metadevices, we demonstrate a new class of spatially varying digital metasurfaces where the local dielectric constant can be reconfigured with applied bias voltages. In addition, we reconfigure resonance frequency of split-ring resonators without changing its amplitude by damping one of the two coupled metasurfaces via graphene. Our approach is general enough to implement various metamaterial systems that could yield new applications ranging from electrically switchable cloaking devices to adaptive camouflage systems.
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http://dx.doi.org/10.1126/sciadv.aao1749DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5756094PMC
January 2018

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

Nano Lett 2017 01 29;17(1):551-558. Epub 2016 Dec 29.

Department of Physics, Chalmers University of Technology , 412 96 Göteborg, Sweden.

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.
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http://dx.doi.org/10.1021/acs.nanolett.6b04659DOI Listing
January 2017

Stercoral colitis: diagnostic value of CT findings.

Diagn Interv Radiol 2017 Jan-Feb;23(1):5-9

Department of Radiology, Hacettepe University School of Medicine, Ankara, Turkey; Department of Radiology, Zonguldak Atatürk State Hospital, Zonguldak, Turkey.

Purpose: We aimed to evaluate the CT findings of stercoral colitis (SC).

Methods: Forty-one patients diagnosed with SC between February 2006 and April 2015 were retrospectively reviewed.

Results: Rectosigmoid colon was the most frequently involved segment (100%, n=41). CT findings can be summarized as follows: dilatation >6 cm and wall thickening >3 mm of the affected colon segment (100%, n=41), pericolonic fat stranding (100%, n=41), mucosal discontinuity (14.6 %, n=6), presence of free air (14.6%, n=6), free fluid (9.7%, n=4), and pericolonic abscess (2.4%, n=1). The sign most related with mortality was the length of the affected colon segment >40 cm.

Conclusion: CT has an important role in SC, since life-threatening complications can be easily revealed by this imaging modality. Increased length of involved colon segment (>40 cm) is more likely to be associated with mortality.
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http://dx.doi.org/10.5152/dir.2016.16002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5214077PMC
May 2017

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

AJR Am J Roentgenol 2017 Mar 8;208(3):505-516. Epub 2016 Nov 8.

1 Department of Radiology, Hacettepe University, School of Medicine, Ankara, Turkey, 06100.

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.
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http://dx.doi.org/10.2214/AJR.16.17326DOI Listing
March 2017

Graphene as a Reversible and Spectrally Selective Fluorescence Quencher.

Sci Rep 2016 Sep 22;6:33911. Epub 2016 Sep 22.

Bilkent University, Department of Physics, 06800, Ankara, Turkey.

We report reversible and spectrally selective fluorescence quenching of quantum dots (QDs) placed in close proximity to graphene. Controlling interband electronic transitions of graphene via electrostatic gating greatly modifies the fluorescence lifetime and intensity of nearby QDs via blocking of the nonradiative energy transfer between QDs and graphene. Using ionic liquid (IL) based electrolyte gating, we are able to control Fermi energy of graphene in the order of 1 eV, which yields electrically controllable fluorescence quenching of QDs in the visible spectrum. Indeed, our technique enables us to perform voltage controllable spectral selectivity among quantum dots at different emission wavelengths. We anticipate that our technique will provide tunable light-matter interaction and energy transfer that could yield hybrid QDs-graphene based optoelectronic devices with novel functionalities, and additionally, may be useful as a spectroscopic ruler, for example, in bioimaging and biomolecular sensing. We propose that graphene can be used as an electrically tunable and wavelength selective fluorescence quencher.
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http://dx.doi.org/10.1038/srep33911DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5031993PMC
September 2016

Dynamic tuning of plasmon resonance in the visible using graphene.

Opt Lett 2016 Mar;41(6):1241-4

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.
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http://dx.doi.org/10.1364/OL.41.001241DOI Listing
March 2016

Percutaneous Treatment of Simple Hepatic Cysts: The Long-Term Results of PAIR and Catheterization Techniques as Single-Session Procedures.

Cardiovasc Intervent Radiol 2016 Jun 29;39(6):902-8. Epub 2015 Dec 29.

Department of Radiology, Hacettepe University Faculty of Medicine, 06100, Sıhhiye, Ankara, Turkey.

Purpose: The purpose of our study is to evaluate results of percutaneous aspiration with alcohol sclerotherapy in symptomatic patients with simple hepatic cysts by employing single-session techniques either by a needle or a catheter.

Materials And Methods: We retrospectively included 39 simple hepatic cysts in 35 patients treated via percutaneous aspiration and single-session alcohol sclerotherapy between years 1993 and 2012. Indications were pain (n = 28) or ruling out cystic echinococcus (CE) disease (n = 7). 29 cysts in 26 patients were treated by needle technique (Group A) and ten cysts in nine patients were treated by single-session catheter technique (Group B). Patients were followed for 4-173 months (median: 38 months).

Results: All patients were successfully treated. Before procedure, cyst volumes were 21-676 cc (median: 94 cc). Post-procedure cyst volumes at last follow-up were 0-40 cc (median: 1 cc). The mean decrease in cyst volume was 95.92 ± 2.86 % in all patients (95.96 ± 3.26 % in Group A and 95.80 ± 6.20 % in Group B). There was no statistically significant difference between the volume reduction rates of Group A and Group B. Only one patient, in Group B, developed a major complication, an abscess. Hospitalization period was 1 day for all patients.

Conclusions: For patients with symptomatic simple hepatic cysts smaller than 500 cc in volume by using puncture, aspiration, injection, and reaspiration (PAIR) technique with only needle, single-session alcohol sclerotherapy of 10 min is a safe and effective procedure with high success rate.
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http://dx.doi.org/10.1007/s00270-015-1283-0DOI Listing
June 2016

Caseous Necrosis of Mitral Annulus.

Case Rep Radiol 2015 18;2015:561329. Epub 2015 Aug 18.

Department of Radiology, Hacettepe University Faculty of Medicine, Sıhhiye, 06100 Ankara, Turkey.

Masses or mass-like lesions located in proximity to mitral valve encompass a wide range of differential diagnoses including neoplasias, abscesses, thrombi, and rarely caseous calcification of mitral annulus. Due to asymptomatic presentation, its diagnosis is usually incidental. Echocardiography is the first choice of imaging in evaluation. Cardiac computed tomography (CT) is helpful in establishing diagnosis by showing dense calcifications while cardiac magnetic resonance imaging (MRI) is used primarily as a problem solving tool. Imaging in evaluation of mitral annulus caseous calcification is essential in order to prevent unnecessary operations.
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http://dx.doi.org/10.1155/2015/561329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4556081PMC
September 2015

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

Opt Lett 2015 Jul;40(14):3424-7

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.
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http://dx.doi.org/10.1364/OL.40.003424DOI Listing
July 2015

Strong coupling between localized and propagating plasmon polaritons.

Opt Lett 2015 Jul;40(13):3177-80

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.
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http://dx.doi.org/10.1364/OL.40.003177DOI Listing
July 2015

Anomalous small cardiac vein draining into the superior vena cava.

J Cardiovasc Comput Tomogr 2015 May-Jun;9(3):236-7. Epub 2015 Feb 2.

Department of Radiology, Hacettepe University Faculty of Medicine, Sıhhiye, Ankara 06100, Turkey. Electronic address:

Coronary venous anatomy is little studied, and an abnormal coronary vein drainage is a rarely reported entity. Few cases about abnormal drainage of the great cardiac vein into the superior vena cava have been reported in literature. Herein we present a case of anomalous small cardiac vein draining into superior vena cava.
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http://dx.doi.org/10.1016/j.jcct.2015.01.013DOI Listing
February 2016

Left atrial drainage of the great cardiac vein.

J Cardiovasc Comput Tomogr 2015 May-Jun;9(3):225-6. Epub 2015 Jan 5.

Department of Radiology, Hacettepe University Faculty of Medicine, Sıhhiye, Ankara 06100, Turkey.

Coronary venous anomaly is a less studied and rarely encountered subject in contrast to the coronary arterial system. In this article, we present 2 cases of anomalous great cardiac veins that drain into the left atrium individually.
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http://dx.doi.org/10.1016/j.jcct.2014.12.006DOI Listing
February 2016

Plasmonic band gap engineering of plasmon-exciton coupling.

Opt Lett 2014 Oct;39(19):5697-700

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.
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http://dx.doi.org/10.1364/OL.39.005697DOI Listing
October 2014

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

Opt Express 2014 Sep;22(18):21912-20

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.
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http://dx.doi.org/10.1364/OE.22.021912DOI Listing
September 2014

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

Opt Lett 2014 Sep;39(17):4994-7

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.
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http://dx.doi.org/10.1364/OL.39.004994DOI Listing
September 2014