Search results for "force"

Coexistence of structural and magnetic phases in van der Waals magnet CrI3

2021

CrI3 has raised as an important system to the emergent field of two-dimensional van der Waals magnetic materials. However, it is still unclear why CrI3 which has a ferromagnetic rhombohedral structure in bulk, changed to anti-ferromagnetic monoclinic at thin layers. Here we show that this behaviour is due to the coexistence of both monoclinic and rhombohedral crystal phases followed by three magnetic transitions at TC1 = 61 K, TC2 = 50 K and TC3 = 25 K. Each transition corresponds to a certain fraction of the magnetically ordered volume as well as monoclinic and rhombohedral proportion. The different phases are continuously accessed as a function of the temperature over a broad range of mag…

Multiscale microstructural characterization of particulate-reinforced composite with non-destructive X-ray micro- and nanotomography

2018

Abstract Methods based on X-ray tomography are developed to study the relevant statistical quantities describing the microstructural inhomogeneity of particulate reinforced composites. The developed methods are applied in estimating microstructural inhomogeneity parameters of composites containing metallic glass particles in metal matrix, extruded in varying pressure loads. This study indicates that the critical characteristics with regard to the effect of particle clustering are cluster size and shape, local volume fraction of particles in the cluster and the distance between clusters. The results demonstrate that the spatial distribution of reinforcement is very uneven and the amount of p…

Association between climate and new daily diagnoses of COVID-19

2020

AbstractBackgroundAlthough evidence is accumulating that climate conditions may positively or negatively influence the scale of coronavirus disease 2019 (COVID-19) outbreaks, uncertainty remains concerning the real impact of climate factors on viral transmission. Methods. The number of new daily cases of COVID-19 diagnosed in Verona (Italy) was retrieved from the official website of Veneto Region, while information on daily weather parameters in the same area was downloaded from IlMeteo website, a renowned Italian technological company specialized in weather forecasts. The search period ranged between March 1 to November 11, 2020. The number of new daily COVID-19 cases and meteorological da…

Slower Walking Speed in Older Men Improves Triceps Surae Force Generation Ability

2016

Purpose \ud Older adults walk slower than young adults, but it is not known why. Previous research suggests that ankle plantarflexors may have a crucial role in the reduction of walking speed. The purpose of this study was to investigate age-related differences in triceps surae muscle–tendon function during walking to further investigate the role of plantarflexors in the age-related reduction of walking speed.\ud \ud Methods \ud Medial gastrocnemius and soleus muscle fascicle lengths were measured using ultrasound imaging during walking from 13 young (25 ± 4 yr) men at preferred walking speed and from 13 older (73 ± 5 yr) men at preferred speed and at the young men’s preferred speed. Muscle…

Contribution of musculoskeletal pain to postural balance in community-dwelling people aged 75 years and older.

2010

Background. Balance is among the most important prerequisites for safe and independent mobility. Whether musculoskeletal pain is related to standing balance impairment has received limited attention. The aim of this study was to examine the association of musculoskeletal pain with the control of balance in older people. Methods. A total of 605 participants aged 75 years and older (mean age 80.4, 71 % women) were interviewed about presence and severity of musculoskeletal pain. Balance was measured by a force platform, and impaired balance was defined as a high sway velocity moment or inability to maintain semitandem standing. Results. Musculoskeletal pain was reported by 48% of the participa…

2019

Post-activation potentiation (PAP) is a well-described phenomenon with a short half-life (~28 s) that enhances muscle force production at submaximal levels of calcium saturation (i.e., submaximal levels of muscle activation). It has been largely explained by an increased myosin light chain phosphorylation occurring in type II muscle fibers, and its effects have been quantified in humans by measuring muscle twitch force responses to a bout of muscular activity. However, enhancements in (sometimes maximal) voluntary force production detected several minutes after high-intensity muscle contractions are also observed, which are also most prominent in muscles with a high proportion of type II fi…

Organocatalytic enantioselective synthesis of quinolizidine alkaloids (+)-myrtine, (-)-lupinine, and (+)-epiepiquinamide

2011

The organocatalytic synthesis of quinolizidine alkaloids (+)-myrtine, (-)-lupinine, and (+)-epiepiquinamide is described. It involved, as the key step, an enantioselective intramolecular aza-Michael reaction (IMAMR) catalyzed by Jorgensen catalyst I, affording the common precursor with high enantioselectivity. This compound was subsequently transformed into the three alkaloids in a highly diastereoselective manner. (C) 2011 Elsevier Ltd. All rights reserved.

Misja Baltic Air Policing jako sprawdzian sojuszniczej odpowiedzialności NATO w XXI wieku

2016

Autor artykułu podejmuje się analizy Misji Air Policing w odniesieniu do wypełnienia zobowiązań sojuszniczych państw członkowskich NATO, ze szczególnym naciskiem na polskie zaangażowanie w misję. Tekst przedstawia rys historyczny Misji Air Policing, jej wymiar instytucjonalny, ponadnarodowy i narodowy. Przeprowadzono też syntetyczną próbę ukazania problemu wynikającego z implementacji doktryny sojuszniczej NATO ze szczególnym naciskiem na koncepcję inteligentnej obrony.

A New Entry to the Substituted Pyrrolo[3,2-c]quinoline Derivatives of Biological Interest by Intramolecular Heteroannulation of Internal Imines.

2004

New 1,3,4-substituted pyrrolo[3,2-c]quinoline derivatives were synthesised in good yields by oxidative heteroannulation of internal imines starting from easily prepared substituted 5-(2-aminophenyl)pyrroles and commercially available aryl and heteroaryl aldehydes. The reaction occurs as a one-pot process involving an intramolecular acid catalysed reaction.

Formation and Evolution of Nanoscale Metal Structures on ITO Surface by Nanosecond Laser Irradiations of Thin Au and Ag Films

2012

The effect of nanosecond laser irradiations on 5 nm thick sputter-deposited Au and Ag films on Indium-Tin-Oxide surface is investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). After 500, 750, and 1000 mJ/cm 2 fluence irradiations, the breakup of the Au and Ag films into nanoscale islands is observed as a consequence of fast melting and solidification processes. The mean nanoparticles size and surface density are quantified, as a function of the laser fluence, by the AFM and SEM analyses. In particular, the comparison between the Au and Ag islands reveals the formation of larger islands in the case of Ag for each fixed fluence. The mechanism of the nanoscale …