1,556 research outputs found
Determinants of fibrinogen in an Italian population suffering from claudication. Lower fibrinogen in the south compared to middle and north of Italy. The ADEP Group.
Prospective studies have shown that high plasma levels of fibrinogen are independently associated with the risk of cardiovascular complications. In patients suffering from peripheral vascular disease (PVD) fibrinogen has been shown to be an independent predictor of cardiovascular disease but its determinants have never been examined in this clinical setting. DESIGN AND METHODS: Fibrinogen levels were related to clinical and laboratory variables in 2,111 patients suffering from PVD. We also analyzed whether there was a regional distribution of risk factors. RESULTS: The median values of fibrinogen was 312 mg/dL. The clinical variables examined did not differentiate patients with elevated or normal fibrinogen levels. In particular, patients with ankle/arm pressure ratio < 0.8 did not show a higher prevalence of fibrinogen > 312 mg/dL. Conversely, white blood cell (WBC) count and serum cholesterol levels were significantly associated with high fibrinogen levels (p < 0.0001). Multiple logistic regression analysis demonstrated that areas of Italy were differently associated with high plasma fibrinogen levels (p < 0.03): subjects in the north and middle of Italy having significantly higher values of fibrinogen than subjects in the south of Italy (p < 0.01). A similar regional distribution was observed for WBC count and serum cholesterol levels. INTERPRETATION AND CONCLUSIONS: The regional distribution of risk factors raises the question as to whether the already reported large variability of cardiovascular events so in PVD may be attributed to a non homogeneous distribution of risk factors
Shock models governed by an inverse gamma mixed Poisson process
We study three classes of shock models governed by an inverse gamma mixed Poisson process (IGMP), namely a mixed Poisson process with an inverse gamma mixing distribution. In particular, we analyze (1) the extreme shock model, (2) the delta-shock model, and the (3) cumulative shock model. For the latter, we assume a constant and an exponentially distributed random threshold and consider different choices for the distribution of the amount of damage caused by a single shock. For all the treated cases, we obtain the survival function, together with the expected value and the variance of the failure time. Some properties of the inverse gamma mixed Poisson process are also disclosed
On the Telegraph Process Driven by Geometric Counting Process with Poisson-Based Resetting
We investigate the effects of the resetting mechanism to the origin for a random motion on the real line characterized by two alternating velocities v1 and v2 . We assume that the sequences of random times concerning the motions along each velocity follow two independent geometric counting processes of intensity λ , and that the resetting times are Poissonian with rate ξ> 0 . Under these assumptions we obtain the probability laws of the modified telegraph process describing the position and the velocity of the running particle. Our approach is based on the Markov property of the resetting times and on the knowledge of the distribution of the intertimes between consecutive velocity changes. We obtain also the asymptotic distribution of the particle position when (i) λ tends to infinity, and (ii) the time goes to infinity. In the latter case the asymptotic distribution arises properly as an effect of the resetting mechanism. A quite different behavior is observed in the two cases when v2< 0 < v1 and 0 < v2< v1 . Furthermore, we focus on the determination of the moment-generating function and on the main moments of the process describing the particle position under reset. Finally, we analyse the mean-square distance between the process subject to resets and the same process in absence of resets. Quite surprisingly, the lowest mean-square distance can be found for ξ= 0 , for a positive ξ , or for ξ→ + ∞ depending on the choice of the other parameters
Control of Molecular Packing in Crystal and Electron Communication of Two Ferrocenyl Moieties across Chiral Isomannide or Isosorbide Bridge
Intramolecular electronic communication between electrochemically active groups connected by a bridging moiety can be modified through small changes in the spatial disposition of the redox active moieties and/or by the nature of the central core. In this study, chiral bio-based compounds, namely isomannide and isosorbide, were employed as cheap and easy-to-functionalize chiral scaffolds to bridge two ferrocenyl electroactive moieties. The crystal structures of both bis-ferrocenyl diester complexes were studied and they showed that the chirality of the bridge results in an open or tight helical crystal packing. The electron communication between the two electroactive units in the mixed valent monocations was also investigated using electrochemistry (cyclic voltammetry and differential pulsed voltammetry), and spectroelectrochemistry in the UV-Vis NIR. A computational study through time-dependent DFT was also employed to gain greater insight into the results obtained
Photopolymerization of Ceramic Resins by Stereolithography Process: A Review
Stereolithography is known as one of the best Additive Manufacturing technologies in terms of geometrical and dimensional precision for polymeric materials. In recent years, a lot of studies have shown that the creation of ceramic resins, through a particular combination of monomeric components and ceramic powders, allows to obtain complex shape geometries thanks to the photopolymerization process. This review highlights the characteristics and properties of ceramic resins, peculiarities of the ceramic stereolithography processes, up to the relationship between the composition of the ceramic resin and the complexity of the post-processing phases. The comparison of different studies allows outlining the most common steps for the production of ceramic resins, as well as the physical and chemical compatibility of the different compounds that must be studied for the good feasibility of the process
Renewable Resources for Enantiodiscrimination: Chiral Solvating Agents for NMR Spectroscopy from Isomannide and Isosorbide
A new family of chiral selectors was synthesized in a single synthetic step with yields up to 84% starting from isomannide and isosorbide. Mono- or disubstituted carbamate derivatives were obtained by reacting the isohexides with electron-donating arylisocyanate (3,5-dimethylphenyl- or 3,5-dimethoxyphenyl-) and electron-withdrawing arylisocyanate (3,5-bis(trifluoromethyl)phenyl-) groups to test opposite electronic effects on enantiodifferentiation. Deeper chiral pockets and derivatives with more acidic protons were obtained by derivatization with 1-naphthylisocyanate and p-toluenesulfonylisocyanate, respectively. All compounds were tested as chiral solvating agents (CSAs) in H-1 NMR experiments with rac-N-3,5-dinitrobenzoylphenylglycine methyl ester in order to determine the influence of different structural features on the enantiodiscrimination capabilities. Some selected compounds were tested with other racemic analytes, still leading to enantiodiscrimination. The enantiodiscrimination conditions were then optimized for the best CSA/analyte couple. Finally, a 2D- and 1D-NMR study was performed employing the best performing CSA with the two enantiomers of the selected analyte, aiming to determine the enantiodiscrimination mechanism, the stoichiometry of interaction, and the complexation constant
Accuracy of complex internal channels produced by laser powder bed fusion process
Additive manufacturing (AM) technology has great potential in manufacturing complex internal channels for several applications such as satellite-communication microwave systems. These systems can have complex shapes and make traditional finishing processes a challenge for additive parts. Therefore, it is desirable that the internal surfaces are as close as possible to the tolerance of the field of application. In this study, a complex component, a unique waveguide device with bending, twisting and filtering functionalities, has been designed and manufactured in AlSi10Mg alloy through laser powder bed fusion (L-PBF) process. Three different prototypes with three different curvature (R of 50 mm, 40 mm and 30 mm), operating in Ku/K band, have been manufactured and tested showing a very good agreement with the desired performances. Using 3D scan data, the internal deviations from the CAD model have been evaluated showing an average deviation of the internal areas of about 0.08 mm, 0.046 mm and 0.023 mm from the CAD model for the R of 50 mm, 40 mm and 30 mm respectively The surface roughness measured in the internal channel is about Ra (arithmetic average roughness) of 8 μm ± 1.3 μm and Rz (average maximum height of the roughness profile) of 62.3 μm ± 0.34 μm
Recent Progress in Beam-Based Metal Additive Manufacturing from a Materials Perspective: A Review of Patents
Over the last decade, the enormous potential of metal additive manufacturing (AM) processes has led these technologies to establish their position in many industries. Much effort is being made toward their widespread application; however, much remains to be done to achieve full industrialization of these processes. Therefore, many companies, research centers and universities are investing in comprehensive research and development activities in order to further promote the industrialization of metal AM. This review traces the progress of metal AM technologies through an investigation of patents. In the present study, beam-based metal AM patents were searched through the Orbit Intelligence database. First, the number of patents per year was studied, indicating that, as expected, there is strong growth in AM patenting activities. The patents were afterward examined in order to highlight the key players in the field, and it was found that the main players investing in this market are: multidisciplinary companies, AM machine producers, end users working, especially in the aerospace sector, universities and research centers. The patents were then analyzed to understand the technology domains covered by each key player and their trend of investments. Finally, the patents in the field of Materials and Metallurgy were studied individually to identify the main topics faced by the most used alloy classes: Al-, Ni- and Ti-based alloys and steels. The extensive study of these patents clearly indicated that the main gaps to fill in metal AM are strongly material dependent and that it is possible to find correlations between the alloy classes, their main industrial applications and their specific AM processability issues. The current study provides insights into global trends that can help industrial markets to identify the right investment direction and research to identify topics for future investigation
Radiolabeled native low-density lipoprotein injected into patients with carotid stenosis accumulates in macrophages of atherosclerotic plaque
BACKGROUND:
Accumulation of LDL within the arterial wall appears to play a crucial role in the initiation and progression of . The dynamic sequence of this event has not been fully elucidated in humans.
METHODS AND RESULTS:
In 7 with previous transient ischemic attack or stroke and critical (>70%) , autologous [(125)I]-labeled LDL or [(125)I]-labeled human serum albumin were 24 to 72 hours before endarterectomy. specimens obtained at endarterectomy were analyzed by autoradiography and immunohistochemistry. Autoradiographic study showed that LDL was localized prevalently in the foam cells of plaques, whereas the accumulation in the lipid core was negligible. Immunohistochemistry revealed that foam cells that had accumulated LDL were mostly CD68 positive, whereas a small number were alpha-actin positive. No accumulation of the radiotracer was detected in plaques after injection of human serum albumin. In 3 treated for 4 weeks with vitamin E (900 mg/d), an almost complete suppression of LDL uptake by was observed.
CONCLUSIONS:
This study shows that circulating LDL rapidly in human . The prevalent accumulation of LDL by provides strong support to the hypothesis that these cells play a crucial role in the pathogenesis of atherosclerosis
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