A new software scheme for scatter correction based on a simple radiographic scattering model

In common radiography, image contrast is often limited due mainly to scattered x-rays and noise, decreasing the quantitative usefulness of x-ray images. Several scatter reduction methods based on software correction schemes have been extensively investigated in an attempt to overcome these difficulties, most of which are based on measurement, mathematical-physical modeling, or a combination of both. However, those methods require special equipment, system geometry, and extra manual work to measure scatter characteristics. In this study, we investigated a new software scheme for scatter correction based on a simple radiographic scattering model where the intensity of the scattered x-rays was directly estimated from a single x-ray image using a weighted l¹-norm contextual regularization framework. We implemented the proposed algorithm and performed a systematic simulation and experiment to demonstrate its viability. We also conducted some clinical image studies using patient's image data of breast and L-spine to verify the clinical effectiveness of the proposed scheme. Our results indicate that the degradation of image characteristics by scattered x-rays and noise was effectively recovered by using the proposed software scheme, thus improving radiographic visibility considerably. Graphical abstract The schematic illustrations of scatter suppression methods by using a an antiscatter grid and b a scatter estimation algorithm.

Growth kinetics of Kr nano structures encapsulated by graphene

Graphene can acquire salient properties by the intercalated nano structures, and to functionalize the graphene as designed, understanding the growth kinetics of the nano structures is a prerequisite. In that regards, Kr atoms are selectively intercalated just below the surface graphene of C(0001) by the incidence of low energy Kr ions. The growth kinetics of the encapsulated Kr nano structures is investigated by both scanning tunneling microscopy and molecular dynamics simulations. The intercalation proceeds via defect sites, such as surface vacancies. At room temperature, the thermal diffusion of intercalated Kr is almost frustrated by the strain field of the encapsulating graphene layers, and the growth of Kr nano structures proceeds via the transient mobility of both the intercalating Kr atoms and previously intercalated Kr atoms that are mobilized by collision with the incident Kr ions. At the elevated temperatures where thermal diffusion becomes effective, some Kr nano structures disappear, releasing pressurized Kr atoms, while others coalesce to form blisters via the delamination of the adjacent graphene. Some of the larger blisters explode to leave craters of varying depths at the surface. In contrast to growth on the substrate, the growth of each encapsulated nano structure depends significantly on extrinsic variables, such as surface vacancies and local topography around the nano structure, that affect the Kr diffusion and limit the maximal Kr pressure.

Center of Mass Motion of Short-Range Correlated Nucleon Pairs studied via the A(e,e^{'}pp) Reaction

Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum (k_{F}). A fundamental characteristic of SRC pairs is having large relative momenta as compared to k_{F}, and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton (pp) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the A(e,e^{'}pp) reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to 170  MeV/c, approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω_{0}^{T}<5.58×10^{-8}, Ω_{0}^{V}<6.35×10^{-8}, and Ω_{0}^{S}<1.08×10^{-7} at a reference frequency f_{0}=25  Hz.

Efficacy and safety of etomidate-midazolam for screening colonoscopy in the elderly: A prospective double-blinded randomized controlled study

BACKGROUND AND AIMS

Recent studies have shown that etomidate is associated with fewer serious adverse events than propofol and has a noninferior sedative effect. We investigated whether etomidate-midazolam is associated with fewer cardiopulmonary adverse events and has noninferior efficacy compared to propofol-midazolam for screening colonoscopy in the elderly.

METHODS

A prospective, single-center, double-blinded, randomized controlled trial was performed. Patients aged over 65 years who were scheduled to undergo screening colonoscopy were randomized to receive either etomidate or propofol based on midazolam. The primary outcome was all cardiopulmonary adverse events. The secondary outcomes were vital sign fluctuation (VSF), adverse events disturbing the procedure, and sedation-related outcomes.

RESULTS

The incidence of cardiopulmonary adverse events was higher in the propofol group (72.6%) than in the etomidate group (54.8%) (P = .040). VSF was detected in 17 (27.4%) and 31 (50.0%) patients in the etomidate and propofol groups, respectively (P = .010). The incidence rate of adverse events disturbing the procedure was significantly higher in the etomidate group (25.8%) than in the propofol group (8.1%) (P = .008). Moreover, the incidence rate of myoclonus was significantly higher in the etomidate group (16.1%) than in the propofol group (1.6%) (P = .004). There was no statistical significance between the 2 groups with respect to sedation times and sedation-related outcomes including patients' and endoscopist's satisfaction. In the multivariate analysis, the etomidate group had significantly low odds ratio (OR) associated with VSF (OR: 0.407, confidence interval: 0.179-0.926, P = .032).

CONCLUSIONS

We recommend using etomidate-midazolam in patients with high ASA score or vulnerable to risk factors; propofol-midazolam may be used as a guideline in patients with low ASA score.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and [Formula: see text] credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5-[Formula: see text] requires at least three detectors of sensitivity within a factor of [Formula: see text] of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

Temporary work and depressive symptoms in South Korean workers

Background

In many countries, including South Korea, labour market changes have led to an increase in unstable, temporary jobs. There is evidence that workers in such jobs may experience poorer mental health than those in more stable employment.

Aims

To investigate the association between temporary employment and depressive symptoms in South Korean workers.

Methods

We analysed data from the 2010-2014 Korean Welfare Panel Study (KOWEPS). Employment type was categorized into workers paid per day of labour (day labourers), those on short-term contracts (fixed-term workers) and permanent workers. The association between employment type and depressive symptoms, measured using the Center for Epidemiological Studies Depression scale (CES-D 11), was examined using the generalized estimating equation model.

Results

A total of 3756 workers aged 20-59 were included in the 2010 baseline population. Day labourers had the highest mean CES-D 11 score, followed by fixed-term workers and permanent workers. With the day labourer group as reference, fixed-term workers (β: -1.5027, P < 0.001) and permanent workers (β: -2.1848, P < 0.001) showed statistically significant decreases in depression scores.

Conclusions

Compared with day labourers, fixed-term workers and permanent workers had progressively lower depression scores. The findings of this study suggest that mental health inequalities based on employment type exist in South Korea.