Giant resonance study by 6li scattering

Nuclear incompressibility Knm is an important parameter in the nuclear matter equation of state (EOS). The locations of the isocalar giant monopole resonance (ISGMR) and giant dipole resonance (ISGDR) of nuclei are directly related to Knm and thus can give the most effective constraint on the value of the Knm. In order to determine Knm accurately, a systematic study of the ISGMR and ISGDR over a wide range of nuclei is necessary. Alpha inelastic scattering at small angles has been successfully used to study the ISGMR of heavy and medium nuclei where the monopole resonance is concentrated in a broad peak. For light nuclei (A<40), however, ISGMR strengths are more elusive because the resonance is fragmented and extends to excitation energies above 35 MeV. Other processes give a large physical background at high excitation energy in α inelastic scattering, which makes it difficult to extract strength distributions in this range. As an isoscalar projectile (N=Z), 6Li scattering could be an alternate way to study giant resonances. A better ratio between the resonance peak and the continuum is expected in 6Li scattering due to the low particle emitting threshold. Another important motivation for 6Li scattering study is to explore the possibility of expanding current research from stable nuclei to radioactive nuclei with inverse reactions using 6Li as a target. Data for elastic scattering of 240 MeV 6Li ions and inelastic scattering to low-lying states and giant resonances was taken for 24Mg, 28Si and 116Sn. A data analysis procedure was developed for double folding calculations. The optical potential parameters for 6Li + 24Mg, 6Li + 28Si and 6Li + 116Sn scattering systems were obtained by fitting elastic scattering data. Multipole analyses were carried out for inelastic scattering to high lying isoscalar giant resonances with multipolarities L=0 - 3. The results for the ISGMR and ISGQR are in agreement with those obtained with 240 MeV α scattering, however the agreement for the ISGDR and HEOR is not so good, indicating the uncertainty in extracting these strengths. This work has shown that 240 MeV 6Li scattering is a viable way to study the ISGMR and ISGQR and can be particularly useful in rare isotope studies where 6Li can be used as the target

Fog Formation in Cold Season in Ji’nan, China: Case Analyses with Application of HYSPLIT Model

Fog events almost happened every year in cold season in North China Plain. In this study, hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model was applied to analyze the formation of four fog events occurring in Ji’nan, China, during the period from March 2012 to February 2014. Three types of fog have been distinguished, including radiation fog, advection fog, and frontal fog. When fog events happened, the average surface temperature ranged from near zero to 10°C and the relative humidity was around 90%. Fog events often happened immediately after haze episodes (i.e., fog-haze) and sometimes after light rain. Back trajectory analyses show that the air masses during the fog events mostly came from the local Shandong areas and moved in very slow speed (4–24 km h−1). During the fog events, the humidity along the air trajectories always gradually increased to saturation. The mixed layer depth was small, generally below 400 m at noon and around 100 m at midnight. However, the air temperature exhibited complex variations—sometimes decreased and sometimes kept stable or even increased

Enrollment-stage Backdoor Attacks on Speaker Recognition Systems via Adversarial Ultrasound

Automatic Speaker Recognition Systems (SRSs) have been widely used in voice applications for personal identification and access control. A typical SRS consists of three stages, i.e., training, enrollment, and recognition. Previous work has revealed that SRSs can be bypassed by backdoor attacks at the training stage or by adversarial example attacks at the recognition stage. In this paper, we propose TUNER, a new type of backdoor attack against the enrollment stage of SRS via adversarial ultrasound modulation, which is inaudible, synchronization-free, content-independent, and black-box. Our key idea is to first inject the backdoor into the SRS with modulated ultrasound when a legitimate user initiates the enrollment, and afterward, the polluted SRS will grant access to both the legitimate user and the adversary with high confidence. Our attack faces a major challenge of unpredictable user articulation at the enrollment stage. To overcome this challenge, we generate the ultrasonic backdoor by augmenting the optimization process with random speech content, vocalizing time, and volume of the user. Furthermore, to achieve real-world robustness, we improve the ultrasonic signal over traditional methods using sparse frequency points, pre-compensation, and single-sideband (SSB) modulation. We extensively evaluate TUNER on two common datasets and seven representative SRS models. Results show that our attack can successfully bypass speaker recognition systems while remaining robust to various speakers, speech content, e

Inaudible Adversarial Perturbation: Manipulating the Recognition of User Speech in Real Time

Automatic speech recognition (ASR) systems have been shown to be vulnerable to adversarial examples (AEs). Recent success all assumes that users will not notice or disrupt the attack process despite the existence of music/noise-like sounds and spontaneous responses from voice assistants. Nonetheless, in practical user-present scenarios, user awareness may nullify existing attack attempts that launch unexpected sounds or ASR usage. In this paper, we seek to bridge the gap in existing research and extend the attack to user-present scenarios. We propose VRIFLE, an inaudible adversarial perturbation (IAP) attack via ultrasound delivery that can manipulate ASRs as a user speaks. The inherent differences between audible sounds and ultrasounds make IAP delivery face unprecedented challenges such as distortion, noise, and instability. In this regard, we design a novel ultrasonic transformation model to enhance the crafted perturbation to be physically effective and even survive long-distance delivery. We further enable VRIFLE's robustness by adopting a series of augmentation on user and real-world variations during the generation process. In this way, VRIFLE features an effective real-time manipulation of the ASR output from different distances and under any speech of users, with an alter-and-mute strategy that suppresses the impact of user disruption. Our extensive experiments in both digital and physical worlds verify VRIFLE's effectiveness under various configurations, robustness against six kinds of defenses, and universality in a targeted manner. We also show that VRIFLE can be delivered with a portable attack device and even everyday-life loudspeakers.Comment: Accepted by NDSS Symposium 202

Expansion of Breast Cancer Stem Cells with Fibrous Scaffolds

Cancer stem cells (CSCs) are hypothesized as tumor-initiating cells within tumors and main contributors of tumor growth, metastasis and recurrence. Mammary cancer cells, MCF-7 cells, were cultured on 3D polycaprolactone (PCL) fibrous scaffolds, showing an increased proportion of CSCs. The expression of stem cell markers, including OCT3/4 and SOX2, and breast CSC-specific markers, SOX4 and CD49f, was significantly upregulated, and the mammosphere-forming capability in cells cultured on PCL fibrous scaffolds increased. The fibrous scaffolds also induced the elongation of MCF-7 cells and extended cell proliferation. The increase of CSC properties after being cultured on fibrous scaffolds was further confirmed with two luminal-type mammary cell lines, T47D and SK-BR-3, and a basal-type cell line, MDA-MB-231, by ALDEFLUOR assay and mammosphere formation assay. Moreover, we observed the upregulation of epithelial to mesenchymal transition and increased invasive capability in cells cultured on PCL fibrous scaffolds. These data suggest that the increase of CSC proportion in a 3D culture system may account for the enhanced malignancy. Therefore, our PCL fibrous scaffolds can potentially be used for CSCs enrichment and anti-cancer drug screening