Additively manufactured Ti-6Al-4V thin struts via laser powder bed fusion: Effect of building orientation on geometrical accuracy and mechanical properties

Porous metal lattice structures have a very high potential in biomedical applications, setting as innovative new generation prosthetic devices. Laser powder bed fusion (L-PBF) is one of the most widely used additive manufacturing (AM) techniques involved in the production of Ti6Al4V lattice structures. The mechanical and failure behavior of lattice structures is strongly affected by geometrical imperfections and defects occurring during L-PBF process. Due to the influence of multiple process parameters and to their combined effect, the mechanical properties of these structures are not yet properly understood. Despite the major commitment to characterize and better comprehend lattice structures, little attention has been paid to the impact that single struts have on the overall lattice properties. In this work, the authors have investigated the tensile strength and fatigue behavior of thin L-PBF Ti6Al4V lattice struts at different building orientations (0°, 15°, 45°, and 90°). This investigation has been focused on the effect that microstructural defects (particularly porosity) and actual surface geometry (including surface texture and geometrical errors such as varying cross-section shape and size) have on the mechanical performances of the struts in relation to their building direction. The results have shown that there is a tendency, particularly for low printing angles, of fatigue life to decrease with decreasing of the building angle. This is mainly due to the surge in surface texture and loss in cross-sectional regularity. On the other hand, the monotonic tensile test results have shown a low sensitivity to these factors. The strut failure behavior has been examined employing dynamic digital image correlation (DIC) of tensile tests and scanning electron imaging (SEM) of the fracture surfaces.

Pore-Scale Transport and Two-Phase Fluid Structures in Fibrous Porous Layers: Application to Fuel Cells and Beyond

We present pore-scale simulations of two-phase flows in a reconstructed fibrous porous layer. The three-dimensional microstructure of the material, a fuel cell gas diffusion layer, is acquired via X-ray computed tomography and used as input for lattice Boltzmann simulations. We perform a quantitative analysis of the multiphase pore-scale dynamics, and we identify the dominant fluid structures governing mass transport. The results show the existence of three different regimes of transport: a fast inertial dynamics at short times, characterised by a compact uniform front, a viscous-capillary regime at intermediate times, where liquid is transported along a gradually increasing number of preferential flow paths of the size of one–two pores, and a third regime at longer times, where liquid, after having reached the outlet, is exclusively flowing along such flow paths and the two-phase fluid structures are stabilised. We observe that the fibrous layer presents significant variations in its microscopic morphology, which have an important effect on the pore invasion dynamics, and counteract the stabilising viscous force. Liquid transport is indeed affected by the presence of microstructure-induced capillary pressures acting adversely to the flow, leading to capillary fingering transport mechanism and unstable front displacement, even in the absence of hydrophobic treatments of the porous material. We propose a macroscopic model based on an effective contact angle that mimics the effects of the such a dynamic capillary pressure. Finally, we underline the significance of the results for the optimal design of face masks in an effort to mitigate the current COVID-19 pandemic.

Conformation and mechanics of the polymeric cuff of artificial urinary sphincter

The surgical treatment of urinary incontinence is often performed by adopting an Artificial Urinary Sphincter (AUS). AUS cuff represents a fundamental component of the device, providing the mechanical action addressed to urethral occlusion, which can be investigated by computational approach. In this work, AUS cuff is studied with reference to both materials and structure, to develop a finite element model. Materials behavior is investigated using physicochemical and mechanical characterization, leading to the formulation of a constitutive model. Materials analysis shows that AUS cuff is composed by a silicone blister joined with a PET fiber-reinforced layer. A nonlinear mechanical behavior is found, with a higher stiffness in the outer layer due to fiber-reinforcement. The cuff conformation is acquired by Computer Tomography (CT) both in deflated and inflated conditions, for an accurate definition of the geometrical characteristics. Based on these data, the numerical model of AUS cuff is defined. CT images of the inflated cuff are compared with results of numerical analysis of the inflation process, for model validation. A relative error below 2.5% was found. This study is the first step for the comprehension of AUS mechanical behavior and allows the development of computational tools for the analysis of lumen occlusion process. The proposed approach could be adapted to further fluid-filled cuffs of artificial sphincters.

Quantification of Wear and Deformation in Different Configurations of Polyethylene Acetabular Cups Using Micro X-ray Computed Tomography

Wear is currently quantified as mass loss of the bearing materials measured using gravimetric methods. However, this method does not provide other information, such as volumetric loss or surface deviation. In this work, we validated a technique to quantify polyethylene wear in three different batches of ultrahigh-molecular-polyethylene acetabular cups used for hip implants using nondestructive microcomputed tomography. Three different configurations of polyethylene acetabular cups, previously tested under the ISO 14242 parameters, were tested on a hip simulator for an additional 2 million cycles using a modified ISO 14242 load waveform. In this context, a new approach was proposed in order to simulate, on a hip joint simulator, high-demand activities. In addition, the effects of these activities were analyzed in terms of wear and deformations of those polyethylenes by means of gravimetric method and micro X-ray computed tomography. In particular, while the gravimetric method was used for weight loss assessment, microcomputed tomography allowed for acquisition of additional quantitative information about the evolution of local wear and deformation through three-dimensional surface deviation maps for the entire cups’ surface. Experimental results showed that the wear and deformation behavior of these materials change according to different mechanical simulations.

Micro X-Ray Computed Tomography Mass Loss Assessment of Different UHMWPE: A Hip Joint Simulator Study on Standard vs. Cross-Linked Polyethylene

More than 60.000 hip arthroplasty are performed every year in Italy. Although Ultra-High-Molecular-Weight-Polyethylene remains the most used material as acetabular cup, wear of this material induces over time in vivo a foreign-body response and consequently osteolysis, pain, and the need of implant revision. Furthermore, oxidative wear of the polyethylene provoke several and severe failures. To solve these problems, highly cross-linked polyethylene and Vitamin-E-stabilized polyethylene were introduced in the last years. In in vitro experiments, various efforts have been made to compare the wear behavior of standard PE and vitamin-E infused liners. In this study we compared the in vitro wear behavior of two different configurations of cross-linked polyethylene (with and without the add of Vitamin E) vs. the standard polyethylene acetabular cups. The aim of the present study was to validate a micro X-ray computed tomography technique to assess the wear of different commercially available, polyethylene’s acetabular cups after wear simulation; in particular, the gravimetric method was used to provide reference wear values. The agreement between the two methods is documented in this paper.

A new predictive model for an improved respiratory isolation strategy in HIV-infected patients with PTB

SETTING

Luigi Sacco Hospital, Milan, Italy, 1 January 2000-31 December 2010.

OBJECTIVES

To develop a predictive score for identifying human immunodeficiency virus (HIV) infected patients with pulmonary tuberculosis (PTB).

DESIGN

Retrospective study based on the medical charts of HIV-infected patients admitted consecutively on presumption of PTB. Patients with culture-positive TB were included in the TB group. Culture-negative subjects formed the non-TB group. Risk factors for PTB were identified and a predictive model was developed. The diagnostic test accuracy of the derived score and that of previously developed scores were analysed.

RESULTS

A total of 65 patients were included in the TB group and 505 subjects in the non-TB group. An eight-variable model (age, origin, alcohol use, respiratory rate, weight loss, haemoglobin, white blood cell count, typical chest X-ray) was derived. When compared with the different scores, this model showed the greatest area under the receiver operating characteristic curve (0.880). This score was the only one to present a negative likelihood ratio of <0.2, which is the threshold for giving strong diagnostic evidence against TB.

CONCLUSIONS

This model may be useful in predicting PTB in HIV patients in low-endemic countries. A validation study is necessary.

Creutzfeldt-Jakob disease with slow progression. A mimickry of progressive supranuclear palsy

Sporadic Creutzfeldt-Jakob disease (sCJD) does not always present with typical clinical signs, such as myoclonus in association with periodic sharp-wave complexes. We present a 67-year old female patient with initial falls and vertical gaze palsy, suggesting the diagnosis of Progressive Supranuclear Palsy (PSP). EEG and MRI were not contributory. Typical clinical and paraclinical CJD signs were only seen after 17 months. The diagnosis was confirmed by autopsy. - CJD can be a neurodegenerative chameleon. The present case adds to the scare literature of slowly evolving CJD mimicking Parkinsonism related to tauopathies.

Monitoring of the heavy-metal hyperaccumulation in vegetal tissues by X-ray radiography and by femto-second laser induced breakdown spectroscopy

This article reports on the utilization of X-ray microradiography and laser induced breakdown spectroscopy (LIBS) techniques for investigation of the metal accumulation in different part of leaf samples. The potential of the LIBS-analysis for finding the proper plant species for phytoremediation is compared with the results of microradiography measurements at the HERCULES source at ENEA, Rome (Italy) and X-ray microradiography experiments at the ELETTRA Synchrotron, Trieste (Italy).

Strain characterization of Echinococcus granulosus protoscoleces of cattle origin using the in vitro vesicular development

The aim of this work was to characterize the strain of protoscoleces of E. granulosus of cattle origin using the in vitro vesicular development. The in vitro development of these samples was compared to samples of sheep origin determined previously by genetic analyses as common sheep strain (G1). There were similarities between sheep and cattle samples not only in the time of microcysts formation, but also in the development process. Vesiculated protoscoleces and protoscoleces with posterior bladders appeared during the first week of incubation. After 14 days of culture, a laminated layer appeared like a fine membrane in one of the extremes of the protoscoleces. In the sheep samples, microcysts were observed between 19 and 20 days. In the cattle samples, microcysts appeared between 20 and 23 days. The coincidence between the development times and physiological characteristics found in the present study may indicate that the parasites from cattle and sheep were of the same strain.

The beamlines of ELETTRA and their application to structural biology

Protein crystallographers are nowadays regular users of synchrotron radiation (SR) facilities for several applications. The goal of majority of users is simply to extract more accurate, higher resolution data from existing crystals; they use monochromatic radiation and the rotation method, in order to get a complete survey of the reciprocal space in a short time. In fact the brilliance of SR is essential, due to the weak scattering power of the samples, and because of their sensibility to radiation damage. Over the last few years, however, a general increase of interest for measurements at multiple wavelengths, which exploit the anomalous dispersion for the phase problem (multiwavelength anomalous diffraction--MAD), has generated the need of intense tuneable sources. For these applications, the emphasis is on accurate measurements of the small differences between the intensities of Bragg reflections at various energies across the absorption edge of an element present in the sample. The macromolecular diffraction beamline at ELETTRA, which is now running routinely since spring 1995, has been designed to provide a high flux--highly collimated tuneable X-rays source in the spectral range between 4 and 25 keV. The radiation source is the 57-pole wiggler, which delivers a very intense radiation up to 25 keV, and is shared and used simultaneously with the small angle X-ray scattering (SAXS) beamline. The front-end filter system has a cut-off energy at about 4 keV. The beamline optics consists of a pseudo-channel-cut double-crystal monochromator followed by a double focusing toroidal mirror. The tunability and the stability of the monochromator allows the user to perform MAD experiments, and for this purpose, a fluorescence probe for the exact calibration of the absorption edge is available on-line. The experimental station is based on an imaging plate area detector from MarResearch, with a sensible area of 345 mm in diameter. A cooled N2-stream is available to cool the sample crystal in order to reduce the radiation damage. SAXS is an experimental technique used to derive structural information about supra-molecular assemblies, amorphous materials and partly ordered systems (e.g. size and shape of large molecules). The high-flux SAXS beamline at ELETTRA is mainly intended for time-resolved studies on fast structural transitions in the sub-millisecond time region in solutions and in partly ordered systems, triggered by external or process parameters, with a SAXS resolution between 10 and 1400 A in real space. The source is the already mentioned 57-pole and the SAXS beamline accepts three discrete energies of its spectrum, namely 5.4, 8 and 16 keV. The beamline optics consists of a flat double-crystal monochromator and a double focusing toroidal mirror. A multi-purpose sample stage, movable along an optical table in order to optimise the sample to detect distance, allows to perform fast time-resolved relaxation studies based on temperature- or pressure-jumps as well as stopped flow experiments. Moreover, the users have option to install their own specialised sample surrounding equipment. The optimisation of the beamline with respect to high-flux and consequently high-flux density, allows to perform the following experiments: low contrast solution scattering, grazing incidence surface diffraction, micro-spot scanning, X-ray fluorescence analysis, time-resolved studies > or = 11 microseconds, simultaneous small- and wide-angle measurements on gels, liquid crystals, biopolymers, amorphous materials, muscles.

Determination by MAD-DM of the structure of the DNA duplex d[ACGTACG(5-BrU)]2 at 1.46 A and 100 K

A four-wavelength MAD experiment on a new brominated octanucleotide is reported here. d[ACGTACG(5-BrU)], C77H81BrN30O32P7, Mr (DNA) = 2235, tetragonal, P43212 (No. 96), a = 43.597, c = 26.268 A, V = 49927.5 A3, Z = 8, T = 100 K, R = 10.91% for 4312 reflections between 15.0 and 1.46 A resolution. The self-complementary brominated octanucleotide d[ACGTACG(5-BrU)]2 has been crystallized and data measured to 1.45 A at both 293 K and a second crystal flash frozen at 100 K. The latter data collection was carried out to the same resolution at the four wavelengths 0.9344, 0.9216, 0.9208 and 0.9003 A, around the Br K edge at 0.92 A and the structure determined from a map derived from a MAD data analysis using pseudo-MIR methodology, as implemented in the program MLPHARE. This is one of the first successful MAD phasing experiments carried out at Sincrotrone Elettra in Trieste, Italy. The structure was refined using the data measured at 0.9003 A, anisotropic temperature factors and the restrained least-squares refinement implemented in the program SHELX96, and the helical parameters are compared with those previously determined for the isomorphous d(ACGTACGT)2 analogue. The asymmetric unit consists of a single strand of octamer with 96 water molecules. No countercations were located. The A-DNA helix geometry obtained has been analysed using the CURVES program.

[An epidemiological study of childhood accidents in the Alto Mantovano area of the Lombardy Region]

BACKGROUND

As part of the regional programme for accident prevention, as much detailed information as possible was collected on the epidemiology of accidents involving children in our local Public Health area. A prospective survey was started of accidents reported to the Emergency Wards of the two hospitals in our Local Public Health area and the outpatient clinics of the pediatricians collaborating with the study. The survey was performed from 1 March to 31 August 1996.

METHODS

A total of 737 reports of accidents involving children aged between 0 and 15 years old (483 males and 254 females) were collected and compared to other series available in the literature. Data were collected using standard forms containing personal details, date, time, place. The form also recorded how the accident occurred, the injuries it caused, the results and the place where First Aid treatment was provided. The causes of accidents were classified using the ICD 9 classification.

RESULTS

Males were the most frequently affected (male-female ratio: 1.9:1) and the ages most frequently involved were 1-5 and over 10 years old; moreover, it was observed that accidents occurred during two peak times: 10-12 a.m. and 4-8 p.m. The most frequent accidents were falls, followed by road accidents and wounds. Among both males and females, the most frequent injuries were those to limbs, followed by cranio-facial injuries; wounds were predominantly surface rather than deep. 13.3% of the cases reported were admitted to hospital.

CONCLUSIONS

These findings underline the importance of the problem even in a non-metropolitan area and the need to make every effort to ensure a safe and serene future for our children.

[Epidemiological study of a primary fibromyalgia in pediatric age]

BACKGROUND

The aim of the present epidemiological research was to select paediatric subjects who were suspicious of Primary Fibromyalgia (PF) and estimate its incidence in the students of the schools of Castiglione delle Stiviere (Mantova).

METHODS

The students had to answer Campbell's questionnaire which was varied and simplified in order to make it comprehensive to everybody even if the key answers were unchanged. The questionnaire was distributed in primary schools (3dr up to 5th class), secondary schools and high schools and its compilation was carried out with a doctor's help. The authors collected and examined 2408 forms. After this evaluation 66 subjects, corresponding to 2.74%, had been considered suspected of PF and had been called to our Paediatric Department to continue the study. In the second phase of the research these 66 students have been submitted to a deep anamnesis, a careful clinical evaluation, a test of tender-points with a digital pressure algometer and some laboratory tests to exclude other rheumatic diseases. The map of the American College of Rheumatology adapted by Wolfe et al. (1990) was used to evaluate tender-points.

RESULTS

After this phase 29 students (1.20%) proved to be affected by primary fibromyalgia.

[An epidemiological study of breast-feeding practice in the referral population of USSL 46 "Alto Mantovano", the Lombardy region. Unità di servizio screening locale]

The aim of this study is to assess the prevalence of breast feeding in the children population of familial advisory bureau in our territory, the reasons for the choice of this kind of nutrition and its duration. The authors also researched if there is some relationship between the choice of feeding and the kind of parturition, mother age, her education and job. The possible influence of the preparatory course of childbirth attendance, mass media and family on this choice was researched to complete the study.

[Echography of the hip in dislocation disease in newborns and infants]

At present, ultrasounds represent the most reliable investigation with images for early C.H.D. diagnosis. This test is innocuous so it can be repeated and furnishes, especially in the first months of life, all those informations the traditional radiology cannot give us. In this work the authors report a clinical and ultrasonographic study of 1116 children (2232 hips); 127 of these were newborns and they have been followed-up from their birth to 7th month of life with ultrasound test at 1.-3.-5.-7. month of life. U.S. investigation has proved itself very sensitive and specific.

[Controlled study on the prevention of respiratory distress syndrome with betamethasone in pregnancy and ACTH and cortisol levels in the premature newborn infant]

The influence of maternal corticosteroid administration was studied on the ACTH and cortisol concentrations in neonatal blood of 24 premature infants whose mothers received betamethasone for prevention of RDS, compared with 11 untreated subjects. Cord blood was taken at birth and from venous sample in 5th day. All samples were analyzed for ACTH and Cortisol by radioimmunoassay. No statistically significant differences between these groups were noted. Additional analysis of ACTH and Cortisol levels in 9 RDS premature infants versus 26 control ones failed to demonstrate any deficiency of corticosteroids in newborn infants with RDS. The findings provide a justification for the prepartum treatment of respiratory distress syndrome with glucocorticoids because this dose of betamethasone does not expose the newborn to potentially harmful effects.

[Current role of acupuncture in analgesic therapy]

After a brief introduction dealing with the great development of acupuncture in management of various painful conditions in the West today, its increased importance, use and role in acute and chronic pain, benign and intractable pain, are discussed. Recent acquisitions about known and yet unknown neurophysiological parameters (evoked cns potentials, endorphines, action of acupuncture in "regulation" of many functions--so called homeostasis--milieu) in connection with good pain relief properties of acupuncture, are referred. The main methods of acupuncture in pain treatment (acupuncture as reflexotherapy--so called electroacupuncture and the very effective auriculotherapy, in comparison with traditional acupuncture as "regulating" method of homeostasis and others minor methods, with our casuistry and positive results in 724 cases of various pain conditions are stressed. Own conclusions about the positive results and the great significance of physician-patient relations in delicate field of pain therapy are referred.

[Prognosis for newborns of very low birthweight (author's transl)]

During the 5 years, 1975-1979, 144 infants weighing less than or equal to 1500 g (ranging from 400 to 1500 g) were admitted to the Neonatal Intensive Care Unit of Mantua. 57 (40%) survived the neonatal period. The principal cause of death was hypoxia and hyaline membrane disease. After leaving the hospital, all the children were seen regularly to 1 year of age and 47 (82%) to 5 years of age. The infants received a neurological and physical evaluation at variable intervals; severe neurological handicaps were found in 2 (3,5%) infants, mild handicaps were observed in 6 (10,5%) infants. Pathological EEG was found in 1 (1,7%) case. The DQ was evaluated by the Gesell test; the DQ was below 80 in 1 child, between 80 and 89 in 2 infants and above 89 in the remaining cases. Three children had strabismus, none had retrolental fibroplasia. Follow-up audiometry was normal in all the subjects. The Authors conclude that intensive care increases the survival and reduces the incidence of serious handicaps in the newborns of very low birthweight.

[Recent acquisitions in reflexo-anesthesia]

Experimental data about the great analgetic value of electro ear-acupuncture stimulation in the cat (by prof. Durinjan--Central Research Institute for reflex-therapy--Moscow) are referred. The mechanism of analgesia by ear electro-stimulation is periacqueductal gray matter (PGM) activation. Trigeminal system as main center involved in this type of acupuncture analgesia is discussed. Up to date parameters for better analgetic results are foreseen.

[Acupunctural electric anesthesia. Comparison between the traditional Chinese technic and combined technic. Preliminary notes]

This preliminary note presents the anaesthetic results obtained in a series of general surgical operations using electro-acupuncture. Comparison between operations carried out under pure acupuncture analgesia of Chinese type and those under combined or mixed electroacupunctural anaesthesia (which involves induction with low doses of drugs and maintenance only by means of acupuncture), shows the evident advantages of the second type in almost all operations.