We have used the Linac Coherent Light Source to generate solid-density aluminum plasmas at temperatures of up to 180 eV. By varying the photon energy of the x rays that both create and probe the ...plasma, and observing the K-α fluorescence, we can directly measure the position of the K edge of the highly charged ions within the system. The results are found to disagree with the predictions of the extensively used Stewart-Pyatt model, but are consistent with the earlier model of Ecker and Kröll, which predicts significantly greater depression of the ionization potential.
Matter with a high energy density (>10(5) joules per cm(3)) is prevalent throughout the Universe, being present in all types of stars and towards the centre of the giant planets; it is also relevant ...for inertial confinement fusion. Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities. With the advent of the Linac Coherent Light Source (LCLS) X-ray laser, high-intensity radiation (>10(17) watts per cm(2), previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated. An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 10(6) kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray-matter interactions, and illustrate the importance of electron-ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Gas transport properties of PIM-1, i.e., the first “polymer with intrinsic microporosity,” at 25°C and different pressures were systematically studied. Permeability coefficients of 10 gases including ...He, H2, N2, O2, CH4, CO2, C2H4, C2H6, C3H6 and C3H8 were conducted at 25°C for five different upstream pressures (from 1 to 10atm). The C2 and C3 hydrocarbons exhibited serious plasticization responses while the permeability coefficients of He, H2, O2, N2, CH4 and CO2 decreased with the trans-membrane pressure as expected from the dual-mobility model. Sorption isotherms of all 10 gases were also determined using a dual-volume sorption cell at 25°C up to a maximum pressure of 27atm. The sorption isotherms followed the dual-mode sorption model. The logarithm of the solubility coefficients increased linearly with the critical temperature of the gas and the slope of this plot (0.018) was found to be comparable with values reported for other glassy polymers. Diffusion coefficients were calculated from the permeability and solubility data; the values for He, H2, O2, N2, CH4 and CO2, increased with pressure as predicted by the dual-mobility model while those of the C2 and C3 hydrocarbon gases increased more strongly because of plasticization. Parameters from the dual mobility model, DD and DH, were significantly higher and their ratio, DH/DD was significantly smaller than those of previously reported polymers.
► Sorption isotherms for various gases in PIM-1 were measured. ► Permeability coefficients for various gases in PIM-1 were measured. ► Results were analyzed by the dual-mode model for glassy polymers.
The newly commissioned Orion laser system has been used to study dense plasmas created by a combination of short pulse laser heating and compression by laser driven shocks. Thus the plasma density ...was systematically varied between 1 and 10 g/cc by using aluminum samples buried in plastic foils or diamond sheets. The aluminum was heated to electron temperatures between 500 and 700 eV allowing the plasma conditions to be diagnosed by K-shell emission spectroscopy. The K-shell spectra show the effect of the ionization potential depression as a function of density. The data are compared to simulated spectra which account for the change in the ionization potential by the commonly used Stewart and Pyatt prescription and an alternative due to Ecker and Kröll suggested by recent x-ray free-electron laser experiments. The experimental data are in closer agreement with simulations using the model of Stewart and Pyatt.
In a prior paper gas sorption, permeation and diffusion coefficients were determined for He, H2, N2, O2, CH4, CO2, C2H4, C2H6, C3H6 and C3H8 in PIM-1, a polymer of intrinsic microporosity, at 25°C ...over a range of pressures. Here similar measurements and analyses were made at temperatures from 25 to 55°C over a wide range of pressure. In all cases, the sorption isotherms were generally consistent with the form of the dual-sorption model. For He, H2, N2, O2, CH4 and CO2, the effects of plasticization were minimal and the results could be effectively analyzed by the dual sorption-dual mobility model, and the temperature dependence of the model parameters were analyzed to obtain the energetic parameters for the sorption and diffusion processes. However, for C2H4, C2H6, C3H6 and C3H8, plasticization was quite significant and temperature dependent; as a result, a similar analysis in terms of the dual sorption-dual mobility model could not be meaningfully carried out. For all gases, a more phenomenological analysis of P, D and S was made in terms of simple Arrhenius and van't Hoff relations to obtain energetic parameters that subsequently depend on pressure because of some combination of dual mode and/or plasticization effects.
Diffusivity and permeability of hydrocarbons in PIM-1 have an inverted temperature dependence due to plasticization Display omitted .
•Sorption, diffusion and permeation isotherms for PIM-1 were measured.•Temperature and pressure dependence of P, D, and S were evaluated.•Energies of sorption, diffusion and permeation were quantified.
Objective To evaluate treatment outcomes of in situ abdominal aortic reconstruction with cryopreserved arterial allograft (CAA) for patients with abdominal aortic infection. Materials and methods A ...retrospective review of prospectively collected data was conducted of patients who underwent in situ aortic reconstruction using CAA for primary, secondary, or prosthetic infection of the abdominal aorta between May 2006 and July 2015, at a single institution. Clinical presentation, indications for treatment, procedural details, early post-operative mortality and morbidity, late death, and graft related complications during the follow up period were investigated. Patient survival and event free survival (any death or re-operation) were calculated using the Kaplan-Meier method. Results Twenty-five patients (male, n = 20, 80%; mean age, 70.2 ± 8.7 years) underwent in situ abdominal aortic reconstruction (48% aortic, 52% aorto-bi-iliac) with vessel size and ABO matched CAA for treatment of abdominal aortic infection caused by infected abdominal aortic aneurysm ( n = 15), aortic prosthesis infection ( n = 7), aortic reconstruction with concomitant colon resection ( n = 2), and primary suppurative aortitis ( n = 1). The median follow up was 19.1 months (range 1–73 months). There were seven post-operative deaths including two (8%) early (<30 days) and five (20%) late deaths There were three (12%) graft related complications including thrombotic occlusion of the CAA, aneurysmal dilatation, and aorto-enteric fistula. Three years after CAA implantation, patient survival was 74% and the event free survival was 58%. Conclusions It is believed that in situ abdominal aortic reconstruction with CAA is a useful option for treating primary, secondary, or prosthetic infection of the abdominal aorta.
Colorectal cancer (CRC) is a leading cause of death in the United States. Increased level of interleukin-8 (IL-8) and CXCR2 on tumours and in the tumour microenvironment has been associated with CRC ...growth, progression and recurrence in patients. Here, we aimed to evaluate the effects of tissue microenvironment-encoded IL-8 and CXCR2 on colon cancer progression and metastasis.
A novel immunodeficient, skin-specific IL-8-expressing transgenic model was generated to evaluate colon cancer growth and metastasis. Syngeneic mouse colon cancer cells were grafted in CXCR2 knockout (KO) mice to study the contribution of CXCR2 in the microenvironment to cancer growth.
Elevated levels of IL-8 in the serum and tumour microenvironment profoundly enhanced the growth of human and mouse colon cancer cells with increased peri-tumoural angiogenesis, and also promoted the extravasation of the cancer cells into the lung and liver. The tumour growth was inhibited in CXCR2 KO mice with significantly reduced tumour angiogenesis and increased tumour necrosis.
Increased expression of IL-8 in the tumour microenvironment enhanced colon cancer growth and metastasis. Moreover, the absence of its receptor CXCR2 in the tumour microenvironment prevented colon cancer cell growth. Together, our study demonstrates the critical roles of the tumour microenvironment-encoded IL-8/CXCR2 in colon cancer pathogenesis, validating the pathway as an important therapeutic target.
The development of robust nano‐ and microstructured catalysts on highly conductive substrates is an effective approach to produce highly active binder‐free electrodes for energy conversion and ...storage applications. As a result, nanostructured electrodes with binder‐free designs have abundant advantages that provide superior electrocatalytic performance; these include more exposed active sites, large surface area, strong adhesion to substrates, facile charge transfer, high conductivity, high intrinsic catalytic activity, and fine‐tuning of its electronic nature through nanostructure modification. Notably, the interface chemistry of an electrocatalyst plays a significant role in their optimized electrocatalytic activity and stability. This review provides an overview of recent progress in nano‐ and microstructured catalysts, such as one, two, and 3D catalysts as binder‐free electrodes for electrocatalytic water splitting via the hydrogen evolution reaction and oxygen evolution reaction, and beyond. Furthermore, this review focuses on the current challenges and synthesis strategies of binder‐free electrodes, with a focus on the impact of nanostructure on their functional property relationships and enhanced bifunctional electrocatalytic performance. Finally, an outlook for their future advances in energy conversion and storage is provided.
The development of robust 1D, 2D, and 3D structured binder‐free electrodes with designed properties and architectures has led to advances in bifunctional electrocatalytic water splitting, photoelectrochemical water splitting, and photocatalysis. This review highlights the state‐of‐the‐art of binder‐free nano‐ and microstructures, from approaches based on well‐regulated fabrication to their successful application for electrocatalytic hydrogen evolution reaction/oxygen evolution reaction and photocatalysis.
South Asian emissions of fossil fuel SO2and black carbon increased ≈6-fold since 1930, resulting in large atmospheric concentrations of black carbon and other aerosols. This period also witnessed ...strong negative trends of surface solar radiation, surface evaporation, and summer monsoon rainfall. These changes over India were accompanied by an increase in atmospheric stability and a decrease in sea surface temperature gradients in the Northern Indian Ocean. We conducted an ensemble of coupled ocean-atmosphere simulations from 1930 to 2000 to understand the role of atmospheric brown clouds in the observed trends. The simulations adopt the aerosol radiative forcing from the Indian Ocean experiment observations and also account for global increases in greenhouse gases and sulfate aerosols. The simulated decreases in surface solar radiation, changes in surface and atmospheric temperatures over land and sea, and decreases in monsoon rainfall are similar to the observed trends. We also show that greenhouse gases and sulfates, by themselves, do not account for the magnitude or even the sign in many instances, of the observed trends. Thus, our simulations suggest that absorbing aerosols in atmospheric brown clouds may have played a major role in the observed regional climate and hydrological cycle changes and have masked as much as 50% of the surface warming due to the global increase in greenhouse gases. The simulations also raise the possibility that, if current trends in emissions continue, the subcontinent may experience a doubling of the drought frequency in the coming decades.
Conventional surgical site infection (SSI) surveillance is labour-intensive. We aimed to develop machine learning (ML) models for the surveillance of SSIs for colon surgery and to assess whether the ...ML could improve surveillance process efficiency.
This study included cases who underwent colon surgery at a tertiary center between 2013 and 2014. Logistic regression and four ML algorithms including random forest (RF), gradient boosting (GB), and neural networks (NNs) with or without recursive feature elimination (RFE) were first trained on the entire cohort, and then re-trained on cases selected based on a previous rule-based algorithm. We assessed model performance based on the area under the curve (AUC), sensitivity, and positive predictive value (PPV). The estimated proportion of reduction in workload for chart review based on the ML models was evaluated and compared with the conventional method.
At a sensitivity of 95%, the NN with RFE using 29 variables had the best performance with an AUC of 0.963 and PPV of 21.1%. When combining both the rule-based algorithm and ML algorithms, the NN with RFE using 19 variables had a higher PPV (28.9%) than with the ML algorithm alone, which could decrease the number of cases requiring chart review by 83.9% compared with the conventional method.
We demonstrated that ML can improve the efficiency of SSI surveillance for colon surgery by decreasing the burden of chart review while providing high sensitivity. In particular, the hybrid approach of ML with a rule-based algorithm showed the best performance in terms of PPV.
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