Fibre behaviour in the spunbonding process. Part II: Modelling fibre dynamics in the diffuser

The behaviour of a fibre subject to the turbulent air flow in the diffuser in the spunbonding process is studied using a three-dimensional dynamics model in which the fibre is discretised as a chain of beads connected by linear and rotational springs. The turbulent air drag acting on the fibre is modelled as a random force, as a function of the mean air velocity, the turbulence intensity, and the spectrum of turbulence. The effect of the air flow parameters and the fibre diameter on the amplitude and the frequency of the fibre oscillations is analysed to understand how the fibre position at the exit of the diffuser is controlled by the turbulent air flow in spunbonding. This in turn will affect fibre laydown and the associated web formation. The authors are grateful to Fitesa Germany GmbH for the financial support.This is the author accepted manuscript. The final version is available from SAGE via http://dx.doi.org/10.1177/095440621561698

Fibre behaviour in the spunbonding process. Part I: Characterisation of air flow and fibre motion in the diffuser

This is the author accepted manuscript. The final version is available from SAGE via https://doi.org/10.1177/0954406215616983 The random fibre oscillatory behaviour induced by turbulence in the diffuser of an industrial spunbonding rig is measured experimentally. The turbulent air flow is firstly characterised by constant temperature hot-wire anemometry: averaged flow quantities, such as the mean velocity and the turbulent kinetic energy, as well as time dependent quantities, such as the integral time and the energy spectrum, are measured. The influence of the turbulent flow on the dynamics of a nylon fibre of diameter 200 µm and a spunbonding fibre of diameter 18 µm in the diffuser is then investigated by extracting the transverse displacement from images acquired by a digital camera. The authors are grateful to Fitesa Germany GmbH for the financial support

Modelling fibre laydown and web uniformity in nonwoven fabric

The mechanical and functional performance of nonwoven fabric critically depends on the fibre architecture. The fibre laydown process plays a key role in controlling this architecture. The fibre dynamic behaviour during laydown is studied through a finite element model which describes the role of the parameters in defining the area covered by a single fibre when deposited on the conveyor belt. The path taken by a fibre is described in terms of the radius of gyration, which characterises the area covered by the fibre in the textile, and the spectrum of curvature, which describes the degree of fibre looping as a function of the arc length. Starting from deterministic and idealised fibre curvature spectra, stochastic Monte Carlo simulations are undertaken to generate full nonwoven web samples and reproduce the uniformity of fibre density. A novel image analysis technique that allows measurement of the uniformity of real spunbonded nonwoven samples from images of textiles is used to confirm the validity of the model. It is shown that the main parameter that governs the fibre density uniformity is the ratio of the fibre spinning velocity to the velocity of conveyor belt, while fibre oscillations prior to deposition play a secondary role.Fitesa Germany gmb

Urgent Carotid Surgery: Is It Still out of Debate?

Patients with symptomatic tight carotid stenosis have an increased short-time risk of stroke and an increased long-term risk of ischaemic vascular events compared with the general population. The aim of this study is to assess the safety, efficacy, and limitations of urgent CEA or CAS, in patients with carotid stenosis greater than 70% and clinically characterized by recurrent TIA or brain damage following a stroke (<2.5 cm). This study involved 28 patients divided into two groups. Group A consisted of sixteen patients who had undergone CEA, and group B consisted of twelve patients who had undergone CAS. Primary endpoints were mortality, neurological morbidity (by NIHSS) and postoperative hemorrhagic cerebral conversion, at 30 days. Ten patients (62.5%) of group A experienced an improvement in their initial neurological deficit while in 4 cases (26%) the deficit remained stable. Two cases of neurologic mortality are presented. At 1 month, 9 patients (75%) of group B experienced an improvement in their initial neurological deficit while 3 patients (25%) had a neurological impairment. Urgent or deferred surgical or endovascular treatment have a satisfactory outcome considering the profile in very high-risk patient population. Otherwise in selected patients CEA seems to be preferred to CAS

Comparison between Cloprostenol-induced and Spontaneous Oestrus Fertility in Dairy Cows

A short calving to conception interval is of main importance to achieve high economic efficiency in dairy cow industry. In order to reduce this interval, several hormonal treatments have been put on the market, in which cloprostenol, a synthetic analogue of prostaglandin F2 (PGF2). The aim of this study was to compare fertility of cloprostenol-induced oestrus to that of spontaneous oestrus in dairy cows. In a group of 525 cows, 280 (treated group) were administered 0.5 mg cloprostenol i.m. after transrectal corpus luteum (CL) detection, and inseminated at detected oestrus during the following week. The other 245 cows (control group) were inseminated during spontaneous oestrus. Whey progesterone concentrations were checked at treatment and at insemination in order to remove from the study cows whose P4 levels indicate a non-functional CL, or a lack of luteolysis respectively. Moreover, cows that were not inseminated due to genital problems were also excluded from this study. Conception (59% vs 54.5%) and calving rates (93.7% vs 93%) were not significantly different between the two groups

Noble metal nanoparticles networks stabilized by rod-like organometallic bifunctional thiols

Rod-like organometallic dithiol containing square-planar Pt(II) centers, i. e., trans,trans-[(H3COCS)Pt(PBu3)(2)(C equivalent to C-C6H4-C6H4-C equivalent to C)(PBu3)(2)Pt(SCOCH3)] was used as bifunctional stabilizing agent for the synthesis of Pd-, Au-, and AgNPs (MNPs). All the MNPs showed diameters of about 4 nm, which can be controlled by carefully modulating the synthesis parameters. Covalent MNPs stabilization occurred through a single S bridge between Pt(II) and the noble metal nanocluster surfaces, leading to a network of regularly spaced NPs with the formation of dyads, as supported by SR-XPS data and by TEM imaging analysis. The chemical nature of NPs systems was also confirmed by EDS and NMR. Comparison between SR-XPS data of MNPs and self-assembled monolayers and multilayers of pristine rod-like dithiols deposited onto polycrystalline gold surfaces revealed an electronic interaction between Pt(II) centers and biphenyl moieties of adjacent ligands, stabilizing the organic structure of the network. The possibility to obtain networks of regularly spaced MNPs opens outstanding perspectives in optoelectronics