Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser

The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a "coherent lock-in" measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.

Direct experimental observation of the gas density depression effect using a two-bunch X-ray FEL beam

The experimental observation of the depression effect in gas devices designed for X-ray free-electron lasers (FELs) is reported. The measurements were carried out at the Linac Coherent Light Source using a two-bunch FEL beam at 6.5 keV with 122.5 ns separation passing through an argon gas cell. The relative intensities of the two pulses of the two-bunch beam were measured, after and before the gas cell, from X-ray scattering off thin targets by using fast diodes with sufficient temporal resolution. At a cell pressure of 140 hPa, it was found that the after-to-before ratio of the intensities of the second pulse was about 17% ± 6% higher than that of the first pulse, revealing lower effective attenuation of the gas cell due to heating by the first pulse and subsequent gas density reduction in the beam path. This measurement is important in guiding the design and/or mitigating the adverse effects in gas devices for high-repetition-rate FELs such as the LCLS-II and the European XFEL or other future high-repetition-rate upgrades to existing FEL facilities.

Hemodynamic Changes Caused by Multiple Stenting in Vertebral Artery Fusiform Aneurysms: A Patient-Specific Computational Fluid Dynamics Study

BACKGROUND AND PURPOSE

The multiple stent placement technique has largely improved the long-term outcomes of intracranial fusiform aneurysms, but the hemodynamic mechanisms remain unclear. In this study, we analyzed the hemodynamic changes caused by different stent-placement strategies in patient-specific models using the computational fluid dynamics technique, aiming to provide evidence for clinical decision-making.

MATERIALS AND METHODS

Ten vertebral artery fusiform aneurysms were included, and their patient-specific computational fluid dynamics models were reconstructed. A fast virtual stent placement technique was used to simulate sequential multiple stent placements (from a single stent to triple stents) in the vertebral artery fusiform aneurysm models. Hemodynamic parameters, including wall shear stress, pressure, oscillatory shear index, relative residence time, and flow pattern, were calculated and compared among groups with different numbers of stents.

RESULTS

Virtual stents were deployed in all 10 cases successfully, consistent with the real stent configuration. Wall shear stress decreased progressively by 7.2%, 20.6%, and 25.8% as the number of stents increased. Meanwhile, relative residence time and pressure increased on average by 11.3%, 15.4%, and 45.0% and by 15.7%, 21.5%, and 28.2%. The oscillatory shear index showed no stable variation trend. Flow patterns improved by weakening the intensity of the vortices and displacing the vortex center from the aneurysmal wall.

CONCLUSIONS

Stent placement modifies hemodynamic patterns in vertebral artery fusiform aneurysms, which might favor thrombosis formation in the aneurysmal sac. This effect is amplified with the number of stents deployed. However, a potential risk of rupture or recanalization exists and should be considered when planning to use the multiple stent placement technique in vertebral artery fusiform aneurysms.

Generating Single-Spike Hard X-Ray Pulses with Nonlinear Bunch Compression in Free-Electron Lasers

A simple method for generating single-spike hard x-ray pulses in free-electron lasers (FELs) has been developed at the Linac Coherent Light Source (LCLS). This is realized by nonlinear bunch compression using 20-pC bunch charge, demonstrated in the hard x-ray regime at 5.6 and 9 keV, respectively. Measurements show about half of the FEL shots containing a single-spike spectrum. At 5.6-keV photon energy, the single-spike shots have a mean pulse energy of about 10  μJ with 70% intensity fluctuation and the pulse full width at half maximum is evaluated to be at 200-as level.

Heterodyne x-ray diffuse scattering from coherent phonons

Here, we report Fourier-transform inelastic x-ray scattering measurements of photoexcited GaAs with embedded ErAs nanoparticles. We observe temporal oscillations in the x-ray scattering intensity, which we attribute to inelastic scattering from coherent acoustic phonons. Unlike in thermal equilibrium, where inelastic x-ray scattering is proportional to the phonon occupation, we show that the scattering is proportional to the phonon amplitude for coherent states. The wavevectors of the observed phonons extend beyond the excitation wavevector. The nanoparticles break the discrete translational symmetry of the lattice, enabling the generation of large wavevector coherent phonons. Elastic scattering of x-ray photons from the nanoparticles provides a reference for heterodyne mixing, yielding signals proportional to the phonon amplitude.

InGaN µLEDs integrated onto colloidal quantum dot functionalized ultra-thin glass

Red-, orange-, and green-emitting integrated optoelectronic sources are demonstrated by transfer printing blue InGaN µLEDs onto ultra-thin glass platforms functionally enhanced with II-VI colloidal quantum dots (CQDs). The forward optical power conversion efficiency of these heterogeneously integrated devices is, respectively, 9%, 15%, and 14% for a blue light absorption over 95%. The sources are demonstrated in an orthogonal frequency division multiplexed (OFDM) visible light communication link reaching respective data transmission rates of 46 Mbps, 44 Mbps and 61 Mbps.

High-flow Nasal Cannula Versus Noninvasive Ventilation for Treatment of Acute Hypoxemic Respiratory Failure in Renal Transplant Recipients

OBJECTIVE

This study aimed to evaluate the outcomes of high-flow nasal cannula (HFNC) oxygen therapy compared with noninvasive ventilation (NIV) for the treatment of acute hypoxemic respiratory failure in renal transplant recipients.

METHODS

Data were retrospectively collected from a tertiary intensive care unit (ICU) from July 1, 2011, to September 31, 2015. All renal recipients who had acute respiratory failure at that period of time were classified into the HFNC or NIV group depending on the initial form of respiratory support.

RESULTS

A total of 38 patients were enrolled in this study. Twenty patients received HFNC and the other 18 received NIV as the initial respiratory support. The ICU mortality in the HFNC group was 5% (1 patient), compared with 22.2% (4 patients) in the NIV group (P = .083). The median length of the ICU stay was 12 days in the HFNC group, compared with 14 days in the NIV group (P = .297). The number of ventilator-free days at day 28 was significantly higher in the HFNC group than in the NIV group (26 ± 3 vs 21 ± 3; P < .001). The incidences of both pneumothorax (0% vs 22.2%; P = .042) and skin breakdown (0% vs 22.2%; P = .042) were significantly lower in the HFNC group.

CONCLUSIONS

In renal transplant recipients with acute hypoxemic respiratory failure secondary to severe pneumonia, HFNC achieved outcomes similar to NIV. In addition, HFNC was associated with an increased number of ventilator-free days at day 28 and fewer complications.

Multicentre randomized controlled trial with sensor-augmented pump vs multiple daily injections in hospitalized patients with type 2 diabetes in China: Time to reach target glucose

AIM

Sensor-augmented pump (SAP) technology, which combines continuous subcutaneous insulin infusion (CSII) and real-time continuous glucose monitoring (RT-CGM), has been available for several years in China. In this study, the time required to reach predefined glycaemic targets with SAP vs multiple daily injection (MDI) therapy was compared in hospitalized patients with type 2 diabetes mellitus (T2DM).

METHODS

Adults (aged 18-65 years) with T2DM treated with insulin and admitted to hospital for glucose management were randomized to either SAP (Medtronic MiniMed™ Paradigm™ 722 system) or MDI with blinded CGM (Medtronic MiniMed CGMS System Gold™) for a 2-week period. Glycaemic targets were defined as three preprandial measurements between 80 and 130mg/dL (4.4 and 7.2mmol/L) and three 2-h postprandial measurements between 80 and 180mg/dL (4.4 and 10.0mmol/L) within the same day.

RESULTS

When data from 81 patients (40 SAP, 41 MDI) were analysed, 21 patients using SAP therapy, compared with six using MDI therapy, achieved their glycaemic targets within 3 days, and their time to reach their glucose targets was significantly shorter (3.7±1.1 vs 6.3±3.1 days for MDI; P<0.001), while three MDI patients failed to reach glycaemic targets within 14 days. SAP vs MDI patients experienced significantly less hypoglycaemia [sensor glucose<50mg/dL (2.8mmol/L): 0.04% vs 0.32%, respectively; P<0.05] and significantly less hyperglycaemia [sensor glucose>180mg/dL (10mmol/L): 21.56% vs 35.03%, respectively; P<0.05].

CONCLUSION

SAP vs MDI therapy in hospitalized patients with T2DM significantly reduced the time required to achieve glycaemic targets, and such systems may be a cost-effective way to improve glucose control and reduce hospital stays in T2DM patients.

Results from the Survey of Antibiotic Resistance (SOAR) 2009-11 and 2013-14 in China

OBJECTIVES

To compare antibiotic susceptibility of community-acquired respiratory bacteria in China during 2009-11 and 2013-14.

METHODS

Susceptibility was determined by Etest(®) (bioMérieux) or disc diffusion according to CLSI, EUCAST and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints, except for azithromycin where Etest(®) breakpoints (in CO2 incubation) were used in place of standard CLSI breakpoints. Statistical significance of differences in susceptibility across time periods was evaluated using Fisher's exact test.

RESULTS

During 2009-11, 434 Streptococcus pneumoniae, 307 Haemophilus influenzae and 140 Moraxella catarrhalis were collected from eight centres and during 2013-14, 208 S. pneumoniae, 185 H. influenzae and 80 M. catarrhalis were collected from five centres. Penicillin-non-susceptible isolates remained stable at ∼66% over both time periods but susceptibility decreased significantly for amoxicillin/clavulanic acid (or amoxicillin) and cefaclor. For H. influenzae, the proportion of β-lactamase-positive isolates and β-lactamase-negative ampicillin-resistant strains (CLSI definition) was higher in 2013-14 (25.4% and 7.0%, respectively) than in 2009-11 (16.3% and 3.6%, respectively), with decreased ampicillin and cephalosporin susceptibility. By 2009-11 and 2013-14, only amoxicillin/clavulanic acid (amoxicillin), levofloxacin, penicillin (intravenously) and chloramphenicol inhibited >70% of S. pneumoniae. During 2013-14, M. catarrhalis showed increasing resistance, with cefaclor and levofloxacin susceptibility decreasing significantly. However, amoxicillin/clavulanic acid, cefuroxime and levofloxacin continued to inhibit >90% of isolates.

CONCLUSIONS

On the whole, antimicrobial susceptibility decreased in China between 2009-11 and 2013-14. In 2013-14, amoxicillin/clavulanic acid, levofloxacin and chloramphenicol were the most active antibacterial agents tested against community-acquired respiratory pathogens when assessed by CLSI, EUCAST or PK/PD breakpoints. Resistance to other antibacterials in China was generally high. Our data demonstrate the need to harmonize breakpoints for these pathogens.

Elk-1-mediated 15-lipoxygenase expression is required for hypoxia-induced pulmonary vascular adventitial fibroblast dynamics

AIM

15-Lipoxygenase (15-LO) is an important factor in the pathogenesis of pulmonary artery hypertension (PAH). However, the role of 15-LO in the adventitia of the pulmonary arterial wall is unclear. The aim of this study was to explore the role of 15-LO in the modulation of pulmonary adventitial fibroblast (PAF) dynamics.

METHODS

Rats were exposed to normoxic or hypoxic (fraction of inspired O₂  = 0.12) treatments for 7 days. PAF proliferation and cell cycle alterations were measured by MTT assay, cell immunofluorescence, flow cytometry and Western blot analysis. The 15-LO promoter was analysed by luciferase reporter and ChIP assays.

RESULTS

Our results showed that hypoxia induced 15-LO expression in PAFs both in vivo and in vitro. In addition, hypoxia stimulated JNK phosphorylation in PAFs. Blocking 15-LO or JNK suppressed 15-LO-induced PAF proliferation and cell cycle alterations. The inhibition of p27^kipl by gene silencing attenuated 15-LO-induced PAF proliferation and cell cycle alterations. Furthermore, JNK inhibition or Elk-1 knockdown suppressed hypoxia-induced 15-LO expression in PAFs. Luciferase reporter and ChIP assays revealed that the 15-LO promoter contains Elk-1-binding sites and also that Elk-1 increased the hypoxia-induced activity of the 15-LO promoter.

CONCLUSION

These results suggest that hypoxia promotes changes in the cellular dynamics of PAFs by inducing 15-LO expression, which leads to vascular adventitial remodelling. The modulation of p27^kipl expression by 15-LO enhances PAF proliferation and cell cycle alterations. Furthermore, the JNK-dependent increase in Elk-1 signalling is required for hypoxia-induced 15-LO expression in PAFs.

Identification of sex-specific urinary biomarkers for major depressive disorder by combined application of NMR- and GC-MS-based metabonomics

Women are more vulnerable to major depressive disorder (MDD) than men. However, molecular biomarkers of sex differences are limited. Here we combined gas chromatography-mass spectrometry (GC-MS)- and nuclear magnetic resonance (NMR)-based metabonomics to investigate sex differences of urinary metabolite markers in MDD, and further explore their potential of diagnosing MDD. Consequently, the metabolite signatures of women and men MDD subjects were significantly different from of that in their respective healthy controls (HCs). Twenty seven women and 36 men related differentially expressed metabolites were identified in MDD. Fourteen metabolites were changed in both women and men MDD subjects. Significantly, the women-specific (m-Hydroxyphenylacetate, malonate, glycolate, hypoxanthine, isobutyrate and azelaic acid) and men-specific (tyrosine, N-acetyl-d-glucosamine, N-methylnicotinamide, indoxyl sulfate, citrate and succinate) marker panels were further identified, which could differentiate men and women MDD patients from their respective HCs with higher accuracy than previously reported sex-nonspecific marker panels. Our findings demonstrate that men and women MDD patients have distinct metabonomic signatures and sex-specific biomarkers have promising values in diagnosing MDD.

[BEDT-TTF][Fe(C2O4)Cl2]: an organic-inorganic hybrid semiconductive antiferromagnet

A radical cation salt composed of an organic donor, BEDT-TTF^1.0+, and a one-dimensional inorganic anion, [Fe(C₂O₄)Cl₂^-]_n, was obtained by electrocrystallization, and was identified as a semiconductor with values of σ_300K = 3.0 × 10^-5 S cm^-1. Spin-canted antiferromagnetic long-range ordering was observed at 5.5 K from ZFCM/FCM/RM measurement and confirmed using AC measurement.

Development Of A Cathode Designing Method To Avoid Electrodes’ Interference During Blisk Electrochemical Machining

<p>Electrochemical machining plays a prominent role in blisk (bladed integrated disk) construction process. Since blisk channel is narrow and twisted, interference between electrodes may happen during electrochemical machining. Therefore, this paper develops a cathode designing method to avoid interference. Firstly, according to theory of electrochemical machining, machined channel is predicted by calculation. Second, with this channel, interference analysis is carried out and a cathode is designed. Finally, the cathode is employed in experiment and no interference appears.</p>

Self-Referenced Coherent Diffraction X-Ray Movie of Ångstrom- and Femtosecond-Scale Atomic Motion

Time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine are used to create a movie of intramolecular motion with a temporal and spatial resolution of 30 fs and 0.3 Å. This high fidelity is due to interference between the nonstationary excitation and the stationary initial charge distribution. The initial state is used as the local oscillator for heterodyne amplification of the excited charge distribution to retrieve real-space movies of atomic motion on ångstrom and femtosecond scales. This x-ray interference has not been employed to image internal motion in molecules before. Coherent vibrational motion and dispersion, dissociation, and rotational dephasing are all clearly visible in the data, thereby demonstrating the stunning sensitivity of heterodyne methods.

Ultrafast dynamics of localized magnetic moments in the unconventional Mott insulator Sr2IrO4

We report a time-resolved study of the ultrafast dynamics of the magnetic moments formed by the [Formula: see text] states in Sr2IrO4 by directly probing the localized iridium 5d magnetic state through resonant x-ray diffraction. Using optical pump-hard x-ray probe measurements, two relaxation time scales were determined: a fast fluence-independent relaxation is found to take place on a time scale of 1.5 ps, followed by a slower relaxation on a time scale of 500 ps-1.5 ns.

Photoinduced Enhancement of the Charge Density Wave Amplitude

Symmetry breaking and the emergence of order is one of the most fascinating phenomena in condensed matter physics. It leads to a plethora of intriguing ground states found in antiferromagnets, Mott insulators, superconductors, and density-wave systems. Exploiting states of matter far from equilibrium can provide even more striking routes to symmetry-lowered, ordered states. Here, we demonstrate for the case of elemental chromium that moderate ultrafast photoexcitation can transiently enhance the charge-density-wave (CDW) amplitude by up to 30% above its equilibrium value, while strong excitations lead to an oscillating, large-amplitude CDW state that persists above the equilibrium transition temperature. Both effects result from dynamic electron-phonon interactions, providing an efficient mechanism to selectively transform a broad excitation of the electronic order into a well-defined, long-lived coherent lattice vibration. This mechanism may be exploited to transiently enhance order parameters in other systems with coupled degrees of freedom.