80 research outputs found

    Variational Quantum Approximate Spectral Clustering for Binary Clustering Problems

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    In quantum machine learning, algorithms with parameterized quantum circuits (PQC) based on a hardware-efficient ansatz (HEA) offer the potential for speed-ups over traditional classical algorithms. While much attention has been devoted to supervised learning tasks, unsupervised learning using PQC remains relatively unexplored. One promising approach within quantum machine learning involves optimizing fewer parameters in PQC than in its classical counterparts, under the assumption that a sub-optimal solution exists within the Hilbert space. In this paper, we introduce the Variational Quantum Approximate Spectral Clustering (VQASC) algorithm - a NISQ-compatible method that requires optimization of fewer parameters than the system size, N, traditionally required in classical problems. We present numerical results from both synthetic and real-world datasets. Furthermore, we propose a descriptor, complemented by numerical analysis, to identify an appropriate ansatz circuit tailored for VQASC.Comment: 21 pages, 6 figure

    Potassium ions as a kinetic controller in ionic double layers for hysteresis-free perovskite solar cells

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    Since ion migration and interaction with external contacts has been regarded as one of the origins for photocurrent density (J)–voltage (V) hysteresis and phase segregation in perovskite solar cells (PSCs) under operational condition, control of ionic movement in organic–inorganic halide perovskites presents a big challenge for achieving hysteresis-free and stable PSCs. As a universal method, potassium doping into bulk perovskite films to minimize or eliminate the hysteresis was proposed. Here, we report direct observation of moderately retarded ion migration in K+-doped (FAPbI3)0.875(CsPbBr3)0.125 perovskite by in situ photoluminescence (PL) imaging. However, more impressive is the effect on the kinetics for generation of the ionic double layer in the vicinity of the contacts as it is reduced by two orders of magnitude on the time scale when devices are doped with K+ as detected by impedance spectroscopy. A significantly reduced hysteresis in the K+-doped perovskite is responsible for more prolonged stability exhibiting ∼96% of initial power conversion efficiency (PCE) after 22 days than relatively short-lived perovskites undoped with K+ ions. This work highlights the clear correlation of ion migration and a fast generation of the double layer close to the contacts with severe hysteresis and long-term instability in PSCs and the importance of K+ ions in reducing the kinetics affecting the ionic attachment to the contact surface

    Detection of primary sites in unknown primary tumors using FDG-PET or FDG-PET/CT

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    <p>Abstract</p> <p>Background</p> <p>Carcinoma of unknown primary tumors (CUP) is present in 0.5%-9% of all patients with malignant neoplasms; only 20%-27% of primary sites are identified before the patients die. Currently, 18F-fluorodeoxy-glucose positron-emission tomography (18F-FDG PET) or PET combined with computed tomography (PET/CT) is widely used for the diagnosis of CUP. However, the diagnostic yield of the primary site varies. The aim of this study was to determine whether PET or PET/CT has additional advantages over the conventional diagnostic workup in detecting the primary origin of CUP.</p> <p>Findings</p> <p>Twenty patients with unknown primary tumors that underwent PET or PET/CT were included in this study. For all patients, the conventional diagnostic workup was unsuccessful in detecting the primary sites. Among 20 patients, 11 had PET scans. The remaining nine patients had PET/CT. In all 20 patients, neither the PET nor PET/CT identified the primary site of the tumor, including six cases with cervical lymph node metastases. The PET and PET/CT revealed sites of FDG uptake other than those associated with known metastases in seven patients, but these findings did not influence patient management or therapy. Two patients had unnecessary invasive diagnostic procedures due to false positive results on the PET or PET/CT.</p> <p>Conclusions</p> <p>Although it is inconclusive because of small sample size of the study, the additional value of PET or PET/CT for the detection of primary sites in patients with CUP might be less than expected; especially in patients that have already had extensive conventional diagnostic workups. Further study is needed to confirm this finding.</p

    Efficacy and Tolerability of Peginterferon Alpha Plus Ribavirin in the Routine Daily Treatment of Chronic Hepatitis C Patients in Korea: A Multi-Center, Retrospective Observational Study

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    Background/Aims: We aimed to evaluate the efficacy and safety of peginterferon plus ribavirin for chronic hepatitis C (CHC) patients under real life setting in Korea. Methods: We retrospectively analyzed the medical records of 758 CHC patients treated with peginterferon plus ribavirin between 2000 and 2008 from 14 university hospitals in the Gyeonggi-Incheon area in Korea. Results: Hepatitis C virus (HCV) genotype 1 was detected in 61.2% of patients, while genotype 2 was detected in 35.5%. Baseline HCV RNA level was &gt;= 6x10(5) IU/mL in 51.6% of patients. The sustained virological response (SVR) rate was 59.6% regardless of genotype; 53.6% in genotype 1 and 71.4% in genotype 2/3. On multivariate analysis, male gender (p=0.011), early virological response (p&lt;0.001), genotype 2/3 (p&lt;0.001), HCV RNA &lt;6x10(5) IU/mL (p=0.005) and adherence to the drug &gt;80% of the planned dose (p&lt;0.001) were associated with SVR. The rate of premature discontinuation was 35.7%. The main reason for withdrawal was intolerance to the drug due to common adverse events or cytopenia (48.2%). Conclusions: Our data suggest that the efficacy of peginterferon and ribavirin therapy in Koreans is better in Koreans than in Caucasians for the treatment of CHC, corroborating previous studies that have shown the superior therapeutic efficacy of this regimen in Asians.This study was supported by the Korean Association for the Study of the Liver in 2009

    YH29407 with anti-PD-1 ameliorates anti-tumor effects via increased T cell functionality and antigen presenting machinery in the tumor microenvironment

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    Among cancer cells, indoleamine 2, 3-dioxygenase1 (IDO1) activity has been implicated in improving the proliferation and growth of cancer cells and suppressing immune cell activity. IDO1 is also responsible for the catabolism of tryptophan to kynurenine. Depletion of tryptophan and an increase in kynurenine exert important immunosuppressive functions by activating regulatory T cells and suppressing CD8+ T and natural killer (NK) cells. In this study, we compared the anti-tumor effects of YH29407, the best-in-class IDO1 inhibitor with improved pharmacodynamics and pharmacokinetics, with first and second-generation IDO1 inhibitors (epacadostat and BMS-986205, respectively). YH29407 treatment alone and anti-PD-1 (aPD-1) combination treatment induced significant tumor suppression compared with competing drugs. In particular, combination treatment showed the best anti-tumor effects, with most tumors reduced and complete responses. Our observations suggest that improved anti-tumor effects were caused by an increase in T cell infiltration and activity after YH29407 treatment. Notably, an immune depletion assay confirmed that YH29407 is closely related to CD8+ T cells. RNA-seq results showed that treatment with YH29407 increased the expression of genes involved in T cell function and antigen presentation in tumors expressing ZAP70, LCK, NFATC2, B2M, and MYD88 genes. Our results suggest that an IDO1 inhibitor, YH29407, has enhanced PK/PD compared to previous IDO1 inhibitors by causing a change in the population of CD8+ T cells including infiltrating T cells into the tumor. Ultimately, YH29407 overcame the limitations of the competing drugs and displayed potential as an immunotherapy strategy in combination with aPD-1

    Observation of gravitational waves from the coalescence of a 2.5−4.5 M⊙ compact object and a neutron star

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    Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

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    Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects
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