Naphthalimide Trifluoroacetyl Acetonate: A Hydrazine-Selective Chemodosimetric Sensor

The trifluoroacetyl acetonate naphthalimide derivative 1 has been synthesized in good yield. In acetonitrile solution, compound 1 reacts selectively with hydrazine (NH2NH2) to give a five-membered ring. This leads to OFF-ON fluorescence with a maximum intensity at 501 nm as well as easily discernible color changes. Based on a readily discernible and reproducible 3.9% change in overall fluorescence intensity, the limit of detection for 1 is 3.2 ppb (0.1 mu M), which is below the accepted limit for hydrazine set by the U.S. Environmental Protection Agency (EPA). Compound 1 is selective for hydrazine over other amines, including NH4OH, NH2OH, ethylenediamine, methylamine, n-butylamine, piperazine, dimethylamine, triethylamine, pyridine, and is not perturbed by environmentally abundant metal ions. When supported on glass-backed silica gel TLC plates, compound 1 acts as a fluorimetric and colorimetric probe for hydrazine vapor at a partial pressure of 9.0 mm Hg, with selectivity over other potentially interfering volatile analytes, including ammonia, methylamine, n-butylamine, formaldehyde, acetaldehyde, H2O2, HCl, and CO2 being observed. Probe 1 can also be used for the detection of hydrazine in HeLa cells and does so without appreciable interference from other biologically abundant amines and metal ions.U.S. National Science Foundation CHE-1057904Robert A. Welch Foundation F-1018CRI project grant from National Research Foundation of Korea (NRF)Korea government (MSIP) 2009-0081566Chemistr

Thermoelectric properties of nanoporous three-dimensional graphene networks

We propose three dimensional-graphene nanonetworks (3D-GN) with pores in the range of 10 similar to 20 nm as a potential candidate for thermoelectric materials. The 3D-GN has a low thermal conductivity of 0.90 W/mK @773 K and a maximum electrical conductivity of 6660 S/m @773 K. Our results suggest a straightforward way to individually control two interdependent parameters, sigma and kappa, in the nanoporous graphene structures to ultimately improve the figure of merit value.open

Impacts of Reforestation on Stabilization of Riverine Water Levels in South Korea

We investigate how reforestation contributed to stabilization of riverine water levels in South Korea. For the purpose, we estimate an equation capturing dynamic relationships among rainfall, upstream-area tree stock, and downstream water levels in three river systems of Hongcheon, Mangyeong, and Hyeongsan, using daily observations of precipitation and water levels for the period from 1985 to 2005. Simulation based on estimation results shows that increase in the tree stock in a river basin leads to a significantly suppressed peaking in riverine water levels in response to an abrupt and concentrated rain in the upstream area. For instance, an hour-long concentration of 100mm rain results in 0.7m rise in water level if the volume of growing stock is 1 million m3 , whereas the rise in water level stays below 0.27m with 5 million m3 in the growing-stock volume

Optical properties of iron-based superconductor LiFeAs single crystal

We have measured the reflectivity spectra of the iron based superconductor LiFeAs (Tc = 17.6 K) in the temperature range from 4 to 300 K. In the superconducting state (T < Tc), the clear opening of the optical absorption gap was observed below 25 cm-1, indicating an isotropic full gap formation. In the normal state (T > Tc), the optical conductivity spectra display a typical metallic behavior with the Drude type spectra at low frequencies, but we found that the introduction of the two Drude components best fits the data, indicating the multiband nature of this superconductor. A theoretical analysis of the low temperature data (T=4K < Tc) also suggests that two superconducting gaps best fit the data and their values were estimated as {\Delta}1 = 1.59 meV and {\Delta}2 = 3.15 meV, respectively. Using the Ferrell-Glover-Tinkham (FGT) sum rule and dielectric function {\epsilon}1({\omega}), the superconducting plasma frequency ({\omega}ps) is consistently estimated to be 6,665 cm-1, implying that about 59 % of the free carriers in the normal state condenses into the SC condensate. To investigate the various interband transition processes (for {\omega} > 200 cm-1), we have also performed the local-density approximation (LDA) band calculation and calculated the optical spectra of the interband transitions. The theoretical results provided a qualitative agreement with the experimental data below 4000 cm-1Comment: 19 pages, 5 figures. This paper has been accepted for publication in New Journal of Physic

Image-Object-Specific Prompt Learning for Few-Shot Class-Incremental Learning

While many FSCIL studies have been undertaken, achieving satisfactory performance, especially during incremental sessions, has remained challenging. One prominent challenge is that the encoder, trained with an ample base session training set, often underperforms in incremental sessions. In this study, we introduce a novel training framework for FSCIL, capitalizing on the generalizability of the Contrastive Language-Image Pre-training (CLIP) model to unseen classes. We achieve this by formulating image-object-specific (IOS) classifiers for the input images. Here, an IOS classifier refers to one that targets specific attributes (like wings or wheels) of class objects rather than the image's background. To create these IOS classifiers, we encode a bias prompt into the classifiers using our specially designed module, which harnesses key-prompt pairs to pinpoint the IOS features of classes in each session. From an FSCIL standpoint, our framework is structured to retain previous knowledge and swiftly adapt to new sessions without forgetting or overfitting. This considers the updatability of modules in each session and some tricks empirically found for fast convergence. Our approach consistently demonstrates superior performance compared to state-of-the-art methods across the miniImageNet, CIFAR100, and CUB200 datasets. Further, we provide additional experiments to validate our learned model's ability to achieve IOS classifiers. We also conduct ablation studies to analyze the impact of each module within the architecture.Comment: 8 pages, 4 figures, 4 table

Automated Sulcal Depth Measurement on Cortical Surface Reflecting Geometrical Properties of Sulci

Sulcal depth that is one of the quantitative measures of cerebral cortex has been widely used as an important marker for brain morphological studies. Several studies have employed Euclidean (EUD) or geodesic (GED) algorithms to measure sulcal depth, which have limitations that ignore sulcal geometry in highly convoluted regions and result in under or overestimated depth. In this study, we proposed an automated measurement for sulcal depth on cortical surface reflecting geometrical properties of sulci, which named the adaptive distance transform (ADT). We first defined the volume region of cerebrospinal fluid between the 3D convex hull and the cortical surface, and constructed local coordinates for that restricted region. Dijkstra’s algorithm was then used to compute the shortest paths from the convex hull to the vertices of the cortical surface based on the local coordinates, which may be the most proper approach for defining sulcal depth. We applied our algorithm to both a clinical dataset including patients with mild Alzheimer’s disease (AD) and 25 normal controls and a simulated dataset whose shape was similar to a single sulcus. The mean sulcal depth in the mild AD group was significantly lower than controls (p = 0.007, normal [mean±SD]: 7.29±0.23 mm, AD: 7.11±0.29) and the area under the receiver operating characteristic curve was relatively high, showing the value of 0.818. Results from clinical dataset that were consistent with former studies using EUD or GED demonstrated that ADT was sensitive to cortical atrophy. The robustness against inter-individual variability of ADT was highlighted through simulation dataset. ADT showed a low and constant normalized difference between the depth of the simulated data and the calculated depth, whereas EUD and GED had high and variable differences. We suggest that ADT is more robust than EUD or GED and might be a useful alternative algorithm for measuring sulcal depth

Whole-brain imaging with receive-only multichannel top-hat dipole antenna RF coil at 7 T MRI

This work investigates the construction and performance of an eight-channel top-hat dipole receiver RF coil with a capacitive plate to increase the longitudinal whole-brain coverage and receiver sensitivity gain in the brain at 7 T MRI. The construction method for top-hat dipole-based receiver RF coil by adjusting the length and structure corresponding to each channel consists of tuning, matching, balun, and detuning circuitry. Electromagnetic simulations were analyzed on a 3-D human model to evaluate B1+ efficiency and specific absorption rate deposition. Coil performance was evaluated in the human head imaging in vivo. EM simulation results indicated a higher B1− sensitivity in the brain and z-directional coverage of the proposed eight-channel receiver RF coil. The MR images were acquired with an identical field of view showing the receiver coverage improvement in the brain when capacitive plates are used. The MR images also show the clear visibility of the complete set of the cervical vertebrae as well as the spinal cord. The acquired MRI results demonstrate the capability of the proposed RF coil to increase the receiver coverage in the longitudinal direction. Moreover, the B1+ efficiency, as well as receiver sensitivity in the brain, can be substantially improved with the use of multilayered capacitive plates of proper shape and size in conjunction with an RF coil