Pcf theory and cardinal invariants of the reals

The additivity spectrum ADD(I) of an ideal I is the set of all regular cardinals kappa such that there is an increasing chain {A_alpha:alpha<kappa\} in the ideal I such that the union of the chain is not in I. We investigate which set A of regular cardinals can be the additivity spectrum of certain ideals. Assume that I=B or I=N, where B denotes the sigma-ideal generated by the compact subsets of the Baire space omega^omega, and N is the ideal of the null sets. For countable sets we give a full characterization of the additivity spectrum of I: a non-empty countable set A of uncountable regular cardinals can be ADD(I) in some c.c.c generic extension iff A=pcf(A).Comment: 9 page

Grain refining in additively manufactured titanium using boron nitride nanosheets

The functionalization of additive manufacturing (AM) powders with nucleating particles has the potential to alter the grain structure, and hence the mechanical properties of 3D printed structures. We have investigated use of hexagonal boron nitride (BN) nanosheets to modify the microstructure of Ti parts produced by laser-based powder bed fusion (PBF-LB). The components were 3D printed from commercially pure titanium (cp-Ti) powders coated with small amounts (1.5 vol% ≈ 0.77 wt%) of BN nanosheets. As a comparison, pure cp-Ti parts were also built under the same processing conditions. Small- and wide-angle X-ray scattering (SAXS-WAXS) analysis of the 3D printed test structures revealed that BN addition significantly refined the α-Ti grain size and randomized the α-Ti texture. It was observed that grain-refined Ti-BN samples were harder and more brittle than their pure cp-Ti counterparts. This research provides new insights for grain refining using functional powder feedstocks with relatively simple powder pre-processing, and may be applied more broadly in laser-based metal AM

Glueball production in radiative J/psi, Upsilon decays

Using a bound-state model of weakly bound gluons for glueballs made of two gluons and a natural generalization of the perturbative QCD formalism for exclusive hadronic processes, we present results for glueball production in radiative J/psi, Upsilon decays into several possible glueball states, including L \not= 0 ones. We perform a detailed phenomenological analysis, presenting results for the more favored experimental candidates and for decay angular distributions.Comment: RevTeX4, 26 pages, 11 eps figure

A SWEEP-PLANE ALGORITHM FOR THE SIMPLIFICATION OF 3D BUILDING MODELS IN THE APPLICATION SCENARIO OF WIND SIMULATIONS

As the number of virtual 3D city models is steadily increasing, so are the possible applications that take advantage of them. 3D models can be used for applications that range from simple graphic visualizations to complex simulations, such as air flow and acoustic simulations. The geometric requirements needed for Computer Aided Engineering (CAE) and Computational Fluid Dynamics (CFD) increase the already very high complexity of processing 3D models. If there are too many small geometric details, mesh generation may fail. In addition it will create small grid cells that consequently lead to a high computation time. So far, the necessary simplifications have been performed in a time consuming manual process. To reduce the preprocessing time for the considered simulation topic, the simplifications and modifications have to be automated. In this paper we introduce a sweep-plane algorithm designed to automatically simplify virtual 3D models (e.g. CityGML) by removing geometry information unnecessary for numerical simulations. The algorithm will search for edges whose length does not reach a predefined threshold and dissolve them by sweeping nearby faces. As a result we obtain a simplified geometry that can be meshed properly. This algorithm serves as a general basis for the creation of future simplification algorithms that may even be applicable to any simulation necessary. For this paper, one of Stuttgart’s city blocks was processed with the developed algorithm and then used in a wind simulation carried out with ANSYS Fluent

Multivalued SK-contractions with respect to b-generalized pseudodistances

A new class of multivalued non-self-mappings, called SK-contractions with respect to b-generalized pseudodistances, is introduced and used to investigate the existence of best proximity points by using an appropriate geometric property. Some new fixed point results in b-metric spaces are also obtained. Examples are given to support the usability of our main result

Single photon sources in 4H-SiC metal-oxide-semiconductor field-effect transistors

We present single photon sources (SPSs) embedded in 4H-SiC metal-oxide-semiconductor fieldeffect transistors (MOSFETs). They are formed in the SiC/SiO2 interface regions of wet-oxidation C-face 4H-SiC MOSFETs and were not found in other C-face and Si-face MOSFETs. Their bright room-temperature photoluminescence (PL) was observed in the range from 550 to 750 nm andrevealed variable multi-peak structures as well as variable peak shifts. We characterized a wide variety of their PL spectra as the inevitable variation of local atomic structures at the interface. Their polarization dependence indicates that they are formed at the SiC side of the interface. We also demonstrate that it is possible to switch on/off the SPSs by a bias voltage of the MOSFET

Diagnosis and outcome of acute respiratory failure in immunocompromised patients after bronchoscopy

Objective: We wished to explore the use, diagnostic capability and outcomes of bronchoscopy added to noninvasive testing in immunocompromised patients. In this setting, an inability to identify the cause of acute hypoxaemic respiratory failure is associated with worse outcome. Every effort should be made to obtain a diagnosis, either with noninvasive testing alone or combined with bronchoscopy. However, our understanding of the risks and benefits of bronchoscopy remains uncertain. Patients and methods: This was a pre-planned secondary analysis of Efraim, a prospective, multinational, observational study of 1611 immunocompromised patients with acute respiratory failure admitted to the intensive care unit (ICU). We compared patients with noninvasive testing only to those who had also received bronchoscopy by bivariate analysis and after propensity score matching. Results: Bronchoscopy was performed in 618 (39%) patients who were more likely to have haematological malignancy and a higher severity of illness score. Bronchoscopy alone achieved a diagnosis in 165 patients (27% adjusted diagnostic yield). Bronchoscopy resulted in a management change in 236 patients (38% therapeutic yield). Bronchoscopy was associated with worsening of respiratory status in 69 (11%) patients. Bronchoscopy was associated with higher ICU (40% versus 28%; p<0.0001) and hospital mortality (49% versus 41%; p=0.003). The overall rate of undiagnosed causes was 13%. After propensity score matching, bronchoscopy remained associated with increased risk of hospital mortality (OR 1.41, 95% CI 1.08-1.81). Conclusions: Bronchoscopy was associated with improved diagnosis and changes in management, but also increased hospital mortality. Balancing risk and benefit in individualised cases should be investigated further

The Effects of Mechanical Stress on the Growth, Differentiation, and Paracrine Factor Production of Cardiac Stem Cells

Stem cell therapies have been clinically employed to repair the injured heart, and cardiac stem cells are thought to be one of the most potent stem cell candidates. The beating heart is characterized by dynamic mechanical stresses, which may have a significant impact on stem cell therapy. The purpose of this study is to investigate how mechanical stress affects the growth and differentiation of cardiac stem cells and their release of paracrine factors. In this study, human cardiac stem cells were seeded in a silicon chamber and mechanical stress was then induced by cyclic stretch stimulation (60 cycles/min with 120% elongation). Cells grown in non-stretched silicon chambers were used as controls. Our result revealed that mechanical stretching significantly reduced the total number of surviving cells, decreased Ki-67-positive cells, and increased TUNEL-positive cells in the stretched group 24 hrs after stretching, as compared to the control group. Interestingly, mechanical stretching significantly increased the release of the inflammatory cytokines IL-6 and IL-1β as well as the angiogenic growth factors VEGF and bFGF from the cells in 12 hrs. Furthermore, mechanical stretching significantly reduced the percentage of c-kit-positive stem cells, but increased the expressions of cardiac troponin-I and smooth muscle actin in cells 3 days after stretching. Using a traditional stretching model, we demonstrated that mechanical stress suppressed the growth and proliferation of cardiac stem cells, enhanced their release of inflammatory cytokines and angiogenic factors, and improved their myogenic differentiation. The development of this in vitro approach may help elucidate the complex mechanisms of stem cell therapy for heart failure