349 research outputs found
A nanostructured look of collagen apatite porosity into human mineralized collagen fibril
Bone tissue is a hierarchical material characterized at nanoscale by the mineralized collagen fibril, a recurring structure mainly composed of apatite minerals, collagen and water. Bone nanostructure has a fundamental role in determining the mechanical behavior of the tissue and its mass transport properties. Diffusion phenomenon allows to maintain an adequate supply of metabolites in the mechanisms of bone remodeling, adaptation and repair. Several analytical and computational models have been developed to analyze and predict bone tissue behavior. However, the fine replication of the natural tissue still represents a challenge. Insights on the structural organization at nanoscale and on the influence of apatite mineral crystals on the diffusion coefficient lead to outline the functional conditions for the development of biomimetic strategies for bone tissue engineering. Thorough understanding of bone nanostructure is essential to improve longevity of bioscaffolds and to decrease the risk of failure by controlling their mechanical and biological performance
A Three-Dimensional Study of the Morphology and Topography of Pericytes in the Microvascular Bed of Skeletal Muscle
Digested tissue specimens and corrosion casts of rat soleus and tibialis anterior muscles were employed for this Scanning Electron Microscopy (SEM) study. The shape, morphology, and position of pericytes were compared to corresponding imprints on the cast surfaces. Pericytes, observed in digested tissue specimens, showed a typical morphological pattern: a central body with two primary processes that run along the capillary in opposite directions. From these primary processes, secondary ones arise and often encircle the vessel almost completely.
On the surface of corrosion casts, roundish imprints were found in the microvascular tree at the same level where digested tissue specimens showed the presence of pericyte bodies. Along and around the cast surface, shallow grooves reproduced the course of the primary and secondary processes. The peculiar tridimensional arrangement of pericytes at the level of capillary bifurcations underlines their role in red cell flow regulation. However, if the mechanical linkage of the pericytes to the endothelium and their contractability is taken into account, additional roles of these perivascular cells may be hypothesized
Restablecimiento de una nueva normalidad biomecánica en las graves deformidades de la rodilla
En las graves alteraciones morfo-estructurales de la rodilla, con inestabilidad en varusvalgus,
las prótesis vinculadas a bisagra simple, tendían a fallar. El presente trabajo se
propone evidenciar que, en tales situaciones, la prótesis vinculada a rotación representa la
solución más idónea para el restablecimiento de una nueva normalidad. 18 pacientes (13
mujeres y 5 hombres) con edad media de 68 años han sido sometidos a intervención para
colocar prótesis de rodilla. Ha sido utilizado el implante Endo-Model® de Waldemar Link®,
prótesis vinculada a rotación. El follow-up medio es de 19 meses con controles a 2, 3, 6 y
12 meses y después anuales. Los resultados han sido: óptimo para 17 pacientes y bueno
para 1 paciente, en el cual se ha verificado la ruptura post-operatoria del tendón
cuadricipital. Nuestra casuística muestra resultados comparables a los de otros autores. No
hemos tenido movilizaciones asépticas o sépticas, ni complicaciones médicas intraoperatorias
y post-operatorias. Consideramos que, en presencia de la correcta indicación
clínica, la utilización de la prótesis vinculada a rotación es preferible a la de deslizamiento
porque disminuye el riesgo de una movilización precoz del implante y del desgaste anormal
de los componentes protésicos, restableciendo una nueva normalidad biomecánica.Peer Reviewe
Is medical device regulatory compliance growing as fast as extended reality to avoid misunderstandings in the future?
Purpose: European Extended Reality (XR) industry is expected to significantly increase by 2025 with an extreme impact on the Healthcare scenario. Considering that the transition period for the Medical Device Regulation 2017/745 (MDR 2017/745) will end in May 2024, purpose of this study is to assess whether the Medical Device Regulatory Compliance is ready to cope with the inclusion of XR and its possible social and economic impact in the world of medical device software (MDSW). Methods: XR publications patterns were evaluated since MDR 2017/745 release on different databases. European normative about MDSW are consulted, followed by the European Database of Medical Devices (EUDAMED). Results: The number of publications on XR have increased since 2017 and healthcare is the third highest-impacted subject area. Specific classes for software have been introduces in the European Nomenclature of Medical Devices (EMDN) and some XR applications have already been registered in EUDAMED classified as MDSW. Conclusions: XR will become intrinsic in everyday medical protocol and guidelines. The establishment of the IEEE Virtual Reality and Augmented Reality Working Group and the statement of VR for remoting surgery as a MDSW in MDCG 2019-11 are demonstration of the necessity of MD regulatory compliance in being able to keep up with the upcoming XR technologies. The Authors agree that the competent authorities should consider intervening in the European Regulative Compliance to cope with the revolution of Phygital in Healthcare and to regulate procedures involving the use of XR in medicine preventing future misunderstanding and criticalities especially for high risk situations
Muscle Oxygen Delivery in the Forearm and in the Vastus Lateralis Muscles in Response to Resistance Exercise: A Comparison Between Nepalese Porters and Italian Trekkers
Altitude ascending represents an intriguing experimental model reproducing physiological and pathophysiological conditions sharing hypoxemia as the denominator. The aim of the present study was to investigate fractional oxygen extraction and blood dynamics in response to hypobaric hypoxia and to acute resistance exercises, taking into account several factors including different ethnic origin and muscle groups. As part of the “Kanchenjunga Exploration & Physiology” project, six Italian trekkers and six Nepalese porters took part in a high altitude trek in the Himalayas. The measurements were carried out at low (1,450 m) and high altitude (HA; 4,780 m). Near-infrared spectroscopy (NIRS)-derived parameters, i.e., Tot-Hb and tissue saturation index (TSI), were gathered at rest and after bouts of 3-min resistive exercise, both in the quadriceps and in the forearm muscles. TSI decreased with altitude, particularly in forearm muscles (from 66.9 to 57.3%), whereas the decrement was less in the quadriceps (from 62.5 to 57.2%); Nepalese porters were characterized by greater values in thigh TSI than Italian trekkers. Tot-Hb was increased after exercise. At altitude, such increase appeared to be higher in the quadriceps. This effect might be a consequence of the long-term adaptive memory due to the frequent exposures to altitude. Although speculative, we suggest a long-term adaptation of the Nepalese porters due to improved oxygenation of muscles frequently undergoing hypoxic exercise. Muscle structure, individual factors, and altitude exposure time should be taken into account to move on the knowledge of oxygen delivery and utilization at altitude
Effect of CLIQ on training of HL-LHC quadrupole magnets
The high-luminosity LHC upgrade requires stronger than LHC low-beta
quadrupole magnets to reach the luminosity goals of the project. The project is
well advanced and HL-LHC quadrupole magnets are currently being commissioned in
US Labs (MQXFA magnets) and CERN (MQXFB magnets). Those are the first Nb3Sn
magnets to be used in any large particle accelerator. At development stages,
many Nb3Sn accelerator sub-scale models showed relatively slow training and
MQXFA magnets were projected to have low tens of quenches before reaching
operational field. Recently it was shown that dedicated capacitor-based devices
can affect Nb3Sn magnet training, and it was suggested that CLIQ, a
capacitor-based device intended for quench protection, can do too. The present
paper investigates effects on training likely induced by CLIQ, using the base
fact that only half the coils in a quadrupole experience upward current
modulation at quench because of capacitor discharge. The study encompasses all
MQXFA production magnets trained at BNL to date. No other high-statistics data
from identical magnets (series) with CLIQ protection exist so far. Implications
and opportunities stemming from data analysis are discussed and conclusions
drawn.Comment: Accepted versio
Modular versus monoblock stem in revision total hip arthroplasty: a systematic review and meta-analysis
Background: Total hip arthroplasty (THA) is estimated to grow in the following decades with a consequent increase of THA revisions (rTHA). This systematic review and meta-analysis aims to compare modular and monoblock stem in rTHA surgery, focusing on clinical and radiological outcomes and complication rates. Methods: A literature search was performed using the following search strategy: ((Modular stem) OR (monolithic stem)) AND (hip review) on PubMed, Scopus, and Cochrane. Randomized controlled trials (RCTs) and observational studies (OS) compared clinical and radiological outcomes, and complication rates for monoblock and modular revision femoral stem were included. The risk of bias was assessed through the Methodological Index for Non-Randomized Studies (MINORS) score. The Review Manager (RevMan) software was used for the meta-analysis. The rate of complications was assessed using odds ratio (OR) with 95% confidence intervals (CIs). Results: The authors included 11 OS and one RCT with 3,671 participants (mean age: 68.4 years old). The mean follow-up was 46.9 months. There was no prevalence of subsidence for one type of stem. Mean subsidence was from 0.92 to 10 mm for modular stem and from 1 to 15 mm for monoblock stem. Postoperative Harris Hip Score (HHS) showed better results with modular stems without statistical significance [mean difference (MD) =1.32; 95% CI: −1.62 to 4.27; P=0.38]. No statistically significant difference was found for dislocations (OR =2.48; 95% CI: 0.67 to 9.14; P=0.17), infections (OR =1.07; 95% CI: 0.51 to 2.23; P=0.86), intraoperative fractures (OR =1.62; 95% CI: 0.42 to 6.21; P=0.48), and postoperative fractures (OR =1.60; 95% CI: 0.55 to 4.64; P=0.39). Conclusions: Modular and monoblock stems show comparable and satisfactory clinical and radiological outcomes for rTHA. Both stems are valid and effective options for managing femoral bone deficit in hip revision surgery. The main limitation of this study is the small number and low quality of enclosed studies that compared the two stems. Moreover, the modular stem is usually used for more complex cases with lower quality femoral bone stock
Visuomotor Integration for Coupled Hand Movements in Healthy Subjects and Patients With Stroke
Many studies have investigated the bilateral upper limb coordination during movements under different motor and visual conditions. Bilateral training has also been proposed as an effective rehabilitative protocol for patients with stroke. However, the factors influencing in-phase vs. anti-phase coupling have not yet been fully explored. In this study, we used a motion capture device based on two infrared distance sensors to assess whether the up and down oscillation of the less functional hand (the non-dominant one in healthy younger and older subjects and the paretic one in patients with stroke) could be influenced by in-phase or anti-phase coupling of the more functional hand and by visual feedback. Similar patterns were found between single hand movements and in-phase coupled movements, whereas anti-phase coupled movements were less ample, less sinusoidal, but more frequent. These features were particularly evident for patients with stroke who showed a reduced waveform similarity of bilateral movements in all conditions but especially for anti-phase movements under visual control. These results indicate that visuomotor integration in patients with stroke could be less effective than in healthy subjects, probably because of the attentional overload required when moving the two limbs in an alternating fashion
Status of the High Field Cable Test Facility at Fermilab
Fermi National Accelerator Laboratory (FNAL) and Lawrence Berkeley National
Laboratory (LBNL) are building a new High Field Vertical Magnet Test Facility
(HFVMTF) for testing superconducting cables in high magnetic field. The
background magnetic field of 15 T in the HFVMTF will be produced by a magnet
provided by LBNL. The HFVMTF is jointly funded by the US DOE Offices of
Science, High Energy Physics (HEP), and Fusion Energy Sciences (FES), and will
serve as a superconducting cable test facility in high magnetic fields and a
wide range of temperatures for HEP and FES communities. This facility will also
be used to test high-field superconducting magnet models and demonstrators,
including hybrid magnets, produced by the US Magnet Development Program (MDP).
The paper describes the status of the facility, including construction,
cryostat designs, top and lambda plates, and systems for powering, and quench
protection and monitoring
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On unsupervised methods for medical image segmentation: Investigating classic approaches in breast cancer dce-mri
Unsupervised segmentation techniques, which do not require labeled data for training and can be more easily integrated into the clinical routine, represent a valid solution especially from a clinical feasibility perspective. Indeed, large-scale annotated datasets are not always available, undermining their immediate implementation and use in the clinic. Breast cancer is the most common cause of cancer death in women worldwide. In this study, breast lesion delineation in Dynamic Contrast Enhanced MRI (DCE-MRI) series was addressed by means of four popular unsupervised segmentation approaches: Split-and-Merge combined with Region Growing (SMRG), k-means, Fuzzy C-Means (FCM), and spatial FCM (sFCM). They represent well-established pattern recognition techniques that are still widely used in clinical research. Starting from the basic versions of these segmentation approaches, during our analysis, we identified the shortcomings of each of them, proposing improved versions, as well as developing ad hoc pre- and post-processing steps. The obtained experimental results, in terms of area-based—namely, Dice Index (DI), Jaccard Index (JI), Sensitivity, Specificity, False Positive Ratio (FPR), False Negative Ratio (FNR)—and distance-based metrics—Mean Absolute Distance (MAD), Maximum Distance (MaxD), Hausdorff Distance (HD)—encourage the use of unsupervised machine learning techniques in medical image segmentation. In particular, fuzzy clustering approaches (namely, FCM and sFCM) achieved the best performance. In fact, for area-based metrics, they obtained DI = 78.23% ± 6.50 (sFCM), JI = 65.90% ± 8.14 (sFCM), sensitivity = 77.84% ± 8.72 (FCM), specificity = 87.10% ± 8.24 (sFCM), FPR = 0.14 ± 0.12 (sFCM), and FNR = 0.22 ± 0.09 (sFCM). Concerning distance-based metrics, they obtained MAD = 1.37 ± 0.90 (sFCM), MaxD = 4.04 ± 2.87 (sFCM), and HD = 2.21 ± 0.43 (FCM). These experimental findings suggest that further research would be useful for advanced fuzzy logic techniques specifically tailored to medical image segmentation.</jats:p
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