Human Bone Samples Research Articles

An explicit micro-FE approach to investigate the post-yield behaviour of trabecular bone under large deformations.

Homogenised finite element (FE) analyses are able to predict osteoporosis-related bone fractures and become useful for clinical applications. The predictions of FE analyses depend on the apparent, heterogeneous, anisotropic, elastic, and yield material properties, which are typically determined by implicit micro-FE (μFE) analyses of trabecular bone. The objective of this study is to explore an explicit μFE approach to determine the apparent post-yield behaviour of trabecular bone, beyond the elastic and yield properties. The material behaviour of bone tissue was described by elasto-plasticity with a von Mises yield criterion closed by a planar cap for positive hydrostatic stresses to distinguish the post-yield behaviour in tension and compression. Two ultimate strains for tension and compression were calibrated to trigger element deletion and reproduce damage of trabecular bone. A convergence analysis was undertaken to assess the role of the mesh. Thirteen load cases using periodicity-compatible mixed uniform boundary conditions were applied to three human trabecular bone samples of increasing volume fractions. The effect of densification in large strains was explored. The convergence study revealed a strong dependence of the apparent ultimate stresses and strains on element size. An apparent quadric strength surface for trabecular bone was successfully fitted in a normalised stress space. The effect of densification was reproduced and correlated well with former experimental results. This study demonstrates the potential of the explicit FE formulation and the element deletion technique to reproduce damage in trabecular bone using μFE analyses. The proper account of the mesh sensitivity remains challenging for practical computing times.

Fast quantitative 3D ultrashort echo time MRI of cortical bone using extended cones sampling.

To investigate the effect of stretching sampling window on quantitative 3D ultrashort TE (UTE) imaging of cortical bone at 3 T. Ten bovine cortical bone and 17 human tibial midshaft samples were imaged with a 3T clinical MRI scanner using an 8-channel knee coil. Quantitative 3D UTE imaging biomarkers, including T1 , , magnetization transfer ratio and magnetization transfer modeling, were performed using radial or spiral Cones sampling trajectories with various durations. Errors in UTE-MRI biomarkers as a function of sampling time were evaluated using radial sampling as a reference standard. For both bovine and human cortical bone samples, no significant differences were observed for all UTE biomarkers (single-component , bicomponent and relative fractions, T1 , magnetization transfer ratio, and magnetization transfer modeling of macromolecular fraction) for spiral sampling windows of 992 µs to 1600 µs compared with a radial sampling window of 688 µs. The total scan time can be reduced by 76% with quantification errors less than 5%. Quantitative UTE-MRI techniques can be greatly accelerated using longer sampling windows without significant quantification errors.

Effect of Calcination on Microstructure Development and Properties of Hydroxyapatite Powders Extracted from Human and Bovine Bones

ABSTRACTThis study represents a comprehensive discussion of hydroxyapatite (HAp) formation from human and bovine bones. The phase formation and surface morphologies of prepared HAp powders were determined by XRD and SEM analyses, respectively. TEM was employed to understand the internal compositions with high magnifications and particle size. FT-IR characterizations provided information about molecular interactions and structures. In order to understand the effect of heat treatment at different temperatures and ultimately to get the desired morphology/particle size of the HAp powders derived from human and bovine, the powder samples were calcined at 700° to 1100°C with an interval of 100°C. At 700°C, the organic components were removed and finally, a carbonate apatite was obtained. The degree of crystallinity and crystallite size were noticed to increase progressively with calcination temperature. The overall results showed that the calcination temperature highly influenced the properties of HAp powders derived from human and bovine bone samples. As expected, higher temperatures led to more pure form of HAp with higher degree of crystallinity, larger crystallite size, and a less porous structure. Besides, the human bone structure, in contrary to the bovine bone, did not show temperature sensitivity by means of crystallite size increase.

The comparison of DNA extraction techniques in human bone and tooth samples exposed to high heat

In the identification of forensic cases, it is critical to obtain information to identify the victimÂ’s identity from burnt bone and tooth remains. When bone and tooth are burned, both their physical and chemical properties change significantly, which prevents anthropological evaluations and successful DNA profiling for identification purposes. Heat causes difficulties in the identification techniques in which bones and teeth are used, depending on the degree of heat exposure. For this reason, with the changes occurring in bone and tooth during combustion, it is necessary to evaluate the results of observation and analysis, and to be used the information obtained in a certain order. It is very difficult to extract DNA from the samples obtained from fire, explosion, motor vehicle and aircraft accidents and other traumatic events by traditional methods. The only biological material available to determine the typing and the identification of missing persons or unknown remains in different situations, such as mass fatality events, wars or socio-political events, is often only human remains. Effective DNA extraction procedures are critical steps in successful DNA analysis of skeletal remains. Due to variations in DNA and heterogeneity within the bone, unfortunately, the only reliable method for obtaining DNA from overly degraded specimens such as burnt bones and teeth in the literature, is still not available. In the study, present extraction methods are compared and as a result it was suggested that phenol-chloroform and Qiagen DNA Mini Kit could be used in routine with a newly developed modified procedure in order to increase efficiency and efficiency in forensic genetic identification.

Bone diagenesis study of the burials from the Pedra do Alexandre archaeological site, Carnaúba dos Dantas, RN

The Pedra do Alexandre archaeological site was a target of several archaeological campaigns, the bone remains from at least 36 human individuals, and charcoal fragments associated to these burials were among the archaeological findings of the campaigns. The radiocarbon dating provided values between 9400±90 BP and 2620±60 BP. However, attempts to dating the bone remain proved fruitless due to the loss of collagen caused by taphonomic processes. From that finding, this research was initiated to assess the degree of diagenetic alteration of the bone remains from the Pedra do Alexandre archaeological site. FTIR and XRD analyses conducted on 6 random human bone samples from the Site and pH measurements in correlated sediments has enabled us to conclude that all the analyzed bone remains were extensively degraded by microbial activity, although in different degrees of alteration.

Collagen degradation as a possibility to determine the post-mortem interval (PMI) of human bones in a forensic context - A survey.

To find out the time since death (PMI) of a human individual, from which only skeletal remains are left is a difficult question to answer, since methods currently available don't bring concrete answers. Subsequent to our validation study on porcine bones, we focused on human bones analysing if collagen degradation would occur at a predictive rate so that the method may be used for PMI-estimation. We tried to reproduce a method for determining the Co/NCo (Collagen to Non-Collagen) ratio of porcine bones Boaks et al. demonstrated in 2014. Our study sample consisted of 37 human bones from a forensic PMI context and 11 archaeological samples; we prepared thin bone sections of 250 µm; after staining the sections we used spectrophotometry for a portion of the samples and stereomicroscopy and digital imaging to analyze the Co/NCo ratio. Detecting the Co/NCo ratio with spectrophotometry produced results much lower than those published by Boaks et al. (2014) on porcine bone samples and much lower than physiologically expected; a similar result we also got in our validation study on porcine bone samples. We, therefore, applied our new method of stereomicroscopy and digital imaging, which we previously tested on porcine bones. The samples of male individuals showed a significant reduction of the Co/NCo ratio correlating to the PMI. Nevertheless, we still consider analyzing the Co/NCo ration of human bone samples not sufficient for forensic issues. Therefore, greater reference data as well as more experience in practice are needed.

A prehistoric cremation burial at Duns Law Farm, near Duns, Scottish Borders

A large prehistoric pit was uncovered during a watching brief on a water main installation. The pit was partially stone-lined and two small scoops were identified at the base. These contained one complete and one partial Beaker vessel. The fills of the pit produced a small quantity of cremated human bone which represented a minimum of four individuals (three adults and a juvenile). Also mixed into the fills were sherds of other Beaker vessels, a few lithics, a stone axehead, and fragments of Neolithic pottery. Radiocarbon determinations produced early Neolithic dates for four samples of human bone and a grain of wheat, and one human bone sample produced a Bronze Age date later than the generally accepted currency of Beaker pottery production in Scotland. Interpretation of this strange collection of material is discussed with reference to Neolithic and Bronze Age burial practices; the evidence for the use of this pit in the Neolithic for cremation burial is a rare find and provides a valuable contribution to our understanding of this period and type of monument.

Uncovering the chemical secrets of burned bones

By examining burned bones, anthropologists can gather clues about how an ancient culture dealt with its dead or cooked its meat. In a new study, researchers report that Fourier transform infrared (FTIR) spectroscopy can not only differentiate bone burned in a fire from unburned bone, but can also distinguish between burned bone and fossilized bone (Anal. Chem. 2018, DOI: 10.1021/acs.analchem.8b02868). David Goncalves of Portugal’s Directorate General for Cultural Heritage and colleagues applied their FTIR-based method on modern human bone samples burned experimentally at various temperatures, cremated human remains from Bronze and Iron Age burial sites, and fossilized bones of ancient reptiles. They found that a characteristic hydroxyl peak reliably identified bone burned at temperatures above 700 oC—indicative of direct exposure to fire—in both modern and ancient bone samples. Fossilized bone, by comparison, rarely showed the hydroxyl signal. Knowing the burn temperature of a bone sample provides informa...

Bone collagen network integrity and transverse fracture toughness of human cortical bone.

Greater understanding of the determinants of skeletal fragility is highly sought due to the great burden that bone affecting diseases and fractures have on economies, societies and health care systems. Being a complex, hierarchical composite of collagen type-I and non-stoichiometric substituted hydroxyapatite, bone derives toughness from its organic phase. In this study, we tested whether early observations that a strong correlation between bone collagen integrity measured by thermomechanical methods and work to fracture exist in a more general and heterogeneous sampling of the population. Neighboring uniform specimens from an established, highly characterized and previously published collection of human cortical bone samples (femur mid-shaft) were decalcified in EDTA. Fifty-four of the original 62 donors were included (26 male and 28 females; ages 21-101 years; aging, osteoporosis, diabetes and cancer). Following decalcification, bone collagen was tested using hydrothermal isometric tension (HIT) testing in order to measure the collagen's thermal stability (denaturation temperature, Td) and network connectivity (maximum rate of isometric tension generation; Max.Slope). We used linear regression and general linear models (GLMs) with several explanatory variables to determine whether relationships between HIT parameters and generally accepted bone quality factors (e.g., cortical porosity, pentosidine content [pen], pyridinoline content [pyd]), age, and measures of fracture toughness (crack initiation fracture toughness, Kinit, and total energy release/dissipation rate evaluated at the point of unstable fast fracture, J-int) were significant. Bone collagen connectivity (Max.Slope) correlated well with the measures of fracture toughness (R2 = 24-35%), and to a lesser degree with bound water fraction (BW; R2 = 7.9%) and pore water fraction (PW; R2 = 9.1%). Significant correlations with age, apparent volumetric bone mineral density (vBMD), and mature enzymatic [pyd] and non-enzymatic collagen crosslinks [pen] were not detected. GLMs found that Max.Slope and vBMD (or BW), with or without age as additional covariate, all significantly explained the variance in Kinit (adjusted-R2 = 36.7-49.0%). Also, the best-fit model for J-int (adjusted-R2 = 35.7%) included only age and Max.Slope as explanatory variables with Max.Slope contributing twice as much as age. Max.Slope and BW without age were also significant predictors of J-int (adjusted-R2 = 35.5%). In conclusion, bone collagen integrity as measured by thermomechanical methods is a key factor in cortical bone fracture toughness. This study further demonstrates that greater attention should be paid to degradation of the overall organic phase, rather than a specific biomarker (e.g. [pen]), when seeking to understand elevated fracture rates in aging and disease.

Preparation of bone powder for FTIR-ATR analysis: The particle size effect

Fourier transform infrared (FTIR) spectroscopy using attenuated total reflection (ATR) is commonly used for the examination of bone. During sample preparation bone is commonly ground, changing the particle size distribution. Although previous studies have examined changes in crystallinity caused by the intensity of grinding using FTIR, the effect of sample preparation (i.e. particle size and bone tissue type) on the FTIR data is still unknown.This study reports on the bone powder particle size effects on mid-IR spectra and within sample variation (i.e. periosteal, mesosteal, trabecular) using FTIR-ATR. Twenty-four archaeological human and faunal bone samples (5 heated and 19 unheated) of different chronological age (Neolithic to post-Medieval) and origin (Belgium, Britain, Denmark, Greece) were ground using either (1) a ball-mill grinder, or (2) an agate pestle and mortar, and split into grain fractions (>500 μm, 250–500 μm, 125–250 μm, 63–125 μm, and 20–63 μm).Bone powder particle size has a strong but predictable effect on the infrared splitting factor (IRSF), carbonate/phosphate (C/P) ratio, and amide/phosphate (Am/P) values. The absorbance and positions of the main peaks, the 2nd derivative components of the phosphate and carbonate bands, as well as the full width at half maximum (FWHM) of the 1010 cm−1 phosphate peak are particle size dependent. This is likely to be because of the impact of the particle size on the short- and long-range crystal order, as well as the contact between the sample and the prism, and hence the penetration depth of the IR light. Variations can be also observed between periosteal, cortical and trabecular areas of bone. We therefore propose a standard preparation method for bone powder for FTIR-ATR analysis that significantly improves accuracy, consistency, reliability, replicability and comparability of the data, enabling systematic evaluation of bone in archaeological, anthropological, paleontological, forensic and biomedical studies.

Impact of anatomical variations on insertion forces

Abstract The choice of a cochlear implant electrode carrier for the individual patient is influenced by cochlear size, as this parameter has an impact on the risk of scala dislocations. Therefore, size and morphology should be represented in artificial cochlear models too, since these are generally used for insertion studies evaluating newly developed cochlear implant electrode carriers and insertion techniques, before human temporal bone studies are applied for. Within this study custom-made electrode carrier test samples were inserted into nine artificial cochlear models of different shape. To fabricate them, four human temporal bone samples have been processed by a serial cross-sectioning technique; the other four samples have been scanned with micro computed tomography. The cochlea was segmented on this data using rotating, midmodiolar slice planes, followed by the generation of a three-dimensional digital model, which finally was projected on a plane and 2D models were milled out of PTFE. The ratios of length to width of the cochlear basal turn of our samples were found to be within previously reported range. For comparative reasons a model used in previous studies was included in this study too. The maximal insertion forces per cochlear model followed a normal distribution. The insertion depth at initial insertion force increase is correlated to the length of cochlear basal turn. Using the here presented cochlear models with varying anatomical measures may help to increase the clinical relevance of insertion studies in artificial cochlear models.

An Automatic Regularization Method: An Application for 3-D X-Ray Micro-CT Reconstruction Using Sparse Data.

X-ray tomography is a reliable tool for determining the inner structure of 3-D object with penetrating X-rays. However, traditional reconstruction methods, such as Feldkamp-Davis-Kress (FDK), require dense angular sampling in the data acquisition phase leading to long measurement times, especially in X-ray micro-tomography to obtain high-resolution scans. Acquiring less data using greater angular steps is an obvious way for speeding up the process and avoiding the need to save huge data sets. However, computing 3-D reconstruction from such a sparsely sampled data set is difficult because the measurement data are usually contaminated by errors, and linear measurement models do not contain sufficient information to solve the problem in practice. An automatic regularization method is proposed for robust reconstruction, based on enforcing sparsity in the 3-D shearlet transform domain. The inputs of the algorithm are the projection data and a priori known expected degree of sparsity, denoted as . The number Cpr can be calibrated from a few dense-angle reconstructions and fixed. Human subchondral bone samples were tested, and morphometric parameters of the bone reconstructions were then analyzed using standard metrics. The proposed method is shown to outperform the baseline algorithm (FDK) in the case of sparsely collected data. The number of X-ray projections can be reduced up to 10% of the total amount 300 projections over 180° with uniform angular step while retaining the quality of the reconstruction images and of the morphometric parameters.

Histologic and Histomorphometric Analysis of Bone Regeneration with Bovine Grafting Material after 24 Months of Healing. A Case Report.

Anorganic bovine bone mineral matrix (ABBMM) has been reported to have osteoconductive properties and no inflammatory or adverse responses when used as grafting material in sinus augmentation procedures. However, controversy remains in regard to degradation rate of ABBMM. The aim of this study was to histologically and histomorphometrically evaluate the degradation of ABBMM in human bone samples obtained in one patient 24 months after sinus augmentation. Materials and Methods: The histologic and histomorphometric analysis was performed by means of light microscopy in three specimens harvested from the same patient, Results: After 24 months the tissue pattern appeared to be composed of residual particles, some in close contact with the newly formed bone, others separated by translucent areas and osteoid tissues. Newly-formed bone presented different levels of maturation and numerous osteocytes, with greater numbers in bone closer to the grafted particles (27.3% vs. 11.2%, p < 0.05). The histomorphometric analysis showed mean values of 40.84% newly-formed bone, 33.58% residual graft material, 23.84% marrow spaces, and 1.69% osteoid tissue, Conclusions: Even though ABBMM underwent considerable resorption, a great amount of residual grafting material was still present after two years of healing following sinus augmentation. This study confirms that the bovine grafts can be classified as long-term degradation materials.

Abstract 1083A: An ex vivo 3D bone metastasis model for prostate cancer

Abstract Introduction: Bone is the preferred site for prostate cancer (PCa) metastases and there is virtually no cure once the tumor is established within this niche. The development of therapeutic strategies against metastatic PCa has been limited by the lack of an all-human preclinical model to: (1) study PCa-bone interactions under physiologically relevant three dimensional (3D) microenvironments, (2) understand how these interactions result in the development of drug resistance, and (3) explore paradigm-changing precision medicine concepts. Methods: Conditionally reprogrammed primary PCa cells (CR-PCa, derived from a lymph node metastatic site) were integrated with our ex vivo human 3D bone tissue platform, as a transformative approach for modeling tumor behavior at the bone niche. The 3D bone tissue was engineered using primary osteoblastic (OSB) cells from human bone samples. These cells were biomimetically assembly with biphasic calcium phosphate microbeads (BCPm) in perfusion microfluidic culture devices. BCPm were used to replicate the 3D cellular network of OSTs in human bone. This 3D tissue model was successfully used to support the osteocytic differentiation of primary human OSB cells within the BCPm structure, while maintaining a single cell layer of osteoblasts on the surface of the 3D tissue resembling the bone endosteum. Results: Integration of the 3D bone tissue with CR-PCa cells resulted in a compromised endosteal layer after only 4 days of coculture, with more apoptotic OSTs in the tissues with CR-PCa vs. no PCa cells controls (P&amp;lt;0.01). For functional analysis, we stained 5 μm sections of the 3D tissues for alkaline phosphatase (ALP, an OSB marker) and sclerostin, an osteocytic marker and major signaling molecule released by embedded OSTs that suppresses osteoblastogenesis. Quantification of immunofluorescence staining revealed that ALP was significantly increased (P&amp;lt;0.05), whereas sclerostin significantly decreased (P&amp;lt;0.01) with the introduction of CR-PCa cells. This OSB phenotype, induced by PCa-bone interactions ex vivo, is entirely consistent with the OSB prostate cancer-bone metastasis niche seen in patients with advanced disease. Conclusions: Our model recapitulates: (1) an OSB monolayer closely resembling the endosteum at the bone/ bone marrow interface, (2) the complex microphysiological features and functions of 3D-networked OSTs, and (3) the interactions of primary PCa cells with osteoblasts and OSTs. Citation Format: Jenny Zilberberg, Saba Choudhary, Eugenia Dziopa, Cirian Mannion, Yair Kissin, Erika Parasido, Christopher Albanese, Woo Lee. An ex vivo 3D bone metastasis model for prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1083A.

Raman Spectroscopy detects changes in Bone Mineral Quality and Collagen Cross-linkage in Staphylococcus Infected Human Bone

Diagnosis of osteomyelitis presents a formidable challenge. Lack of pathognomonic clinical sign(s) and diagnostic tests that can diagnose osteomyelitis at an early stage contribute to this difficulty. If the diagnosis is not made early, the disease becomes very difficult to eradicate and can lead to limb threatening and potentially life-threatening complications. Staphylococcus aureus is the most common organism causing osteomyelitis. Raman Spectroscopy provides information about molecular vibration that could potentially be harnessed as a spectral signature for cellular changes in specific pathologic conditions. In this study we describe a technique using Raman spectroscopy that could potentially be used to diagnose staphylococcal osteomyelitis. Human bone samples were co-cultured with Staphylococcus aureus (S. aureus) and the effects of bacterial growth on bone quality were then monitored using Raman spectroscopy. A major drop in the bone mineral quality and crystallinity was observed in the infected bones compared to the controls. S. aureus infection was also found to alter the collagen cross-linking. Our study shows that specific spectral signatures are present for the cause as well as the effect of staphylococcal osteomyelitis, opening the possibility of developing a useful diagnostic modality for early and rapid diagnosis of this condition.

Determination of 226Ra at low levels in environmental, urine, and human bone samples and 223Ra in bone biopsy using alpha-spectrometry and metrological traceability to 229Th/225Ra or 226Ra

226Ra is a natural radioelement emitting α and γ radiations. It can be highly concentrated in TENORM materials from the petroleum or fertilizer industries. In Switzerland, 226Ra is currently a radioactive inheritance problem from the watch industry. Furthermore, 223Ra is a radium isotope used in nuclear medicine to treat bone metastasis. There exist several methods to measure radium using alpha or gamma spectrometry or using 222Rn emanation technique. The limitations of these methods are due to the required detection limits and the nature of the samples. When using alpha spectrometry to reach very low detection limits, critical technical hitches often arise because of the difficulties in separating radium from barium, in removing organics eluted from the separating chromatography column, and in plating radium. Moreover, overall chemical recovery of radium is often not reproducible, depending on the studies.Here we propose a method that separates radium from other alkaline-earth cations using cation exchange chromatography and selective complex formation by EDTA and DCTA. Radium is completely free of the 229Th tracer and its daughter products, particularly 225Ac. Organics from the column are removed in a further purification step so that radium can be plated with acceptable yields in a HCl/HNO3/ethanol solution. We successfully applied the method to soil, water, urine and human bone samples and further extended it to the determination of 223Ra in a bone biopsy, using 226Ra as an internal tracer.

Temporary implementation and testing of a confocal SR-[formula omitted]XRF system for bone analysis at the X-ray Fluorescence beamline at Elettra

The confocal μXRF spectrometer of Atominstitut (ATI) was transported and set up at the X-ray Fluorescence beamline at Elettra - Sincrotrone Trieste. It was successfully adjusted to the incoming beam (9.2 keV). Test measurements on a free-standing Cu wire were performed to determine the size of the focused micro-beam (non-confocal mode, 56 × 35 μm2) and the size of the confocal volume (confocal mode, 41×24×34μm2) for the Cu–Kα emission. In order to test the setup’s capabilities, two areas on different human bone samples were measured in confocal scanning mode. For one of the samples the comparison with a previous μ XRF measurement, obtained with a low power X-ray tube in the lab, is presented.

Quantifying collagen quality in archaeological bone: Improving data accuracy with benchtop and handheld Raman spectrometers

Chemical analysis of collagen and other endogenous protein in excavated bones is ever more common in paleontology and archaeology to determine dietary ecology, migration patterns, age, and diagenetic pathways. Decisions to sacrifice valuable samples to destructive stable isotope, radiogenic isotope, and proteomic analyses are easier to make if one knows ahead of time whether sufficient undegraded organic material is preserved in the bone for chemical analysis. Recent advances with near–infrared Raman spectroscopy to non-destructively pre-screen bones for the presence of undegraded endogenous protein can indicate whether original isotopic or proteomic signatures have remained intact in long-buried bones. However, it is crucial to examine the different emerging approaches with benchtop and handheld Raman spectrometers and to establish uniform data reporting standards that will allow laboratories to accurately compare results. Three recently published studies are compared to understand the factors that affect protein screening success and to establish best practices for the technique in the laboratory and in the field. A set of 37 archaeological human bone samples analyzed previously by the authors using FT-Raman spectroscopy are re-analyzed with a handheld 1064nm Raman spectrometer such that the laser power was similar but the spectral resolution and signal-to-noise were lower. Two methods to identify peak heights were evaluated: 1) peak height fixed at a specific wavenumber and baseline anchored at fixed points bracketing the band and 2) averaging peak intensities over a short wavenumber range while also setting the baseline of the band by an average of several anchor points. This second method appeared to better classify whether the bones contained well-preserved protein signatures. In particular, peak height ratios of 960cm−1 to 1636cm−1 or 1450cm−1 can indicate quality and abundance of bone protein, but have benefits and trade-offs that depend on the instrument used. The 960cm−1:1636cm−1 ratio is more descriptive of collagen quality as defined by an extracted carbon:nitrogen ratio of 2.8–3.6, but the 1636cm−1 peak can be difficult to resolve well with an inherently less sensitive handheld Raman spectrometer. The 1450cm−1 peak is more prominent in the spectrum and therefore more easily resolved with a handheld spectrometer, but it describes a common CH stretch found in collagen and other organic molecules.

Long-lasting sacred landscapes: The numerical chronology of the megalithic phenomenon in south-eastern Iberia

Thanks to the radiocarbon dating programme undertaken in the last five years, it is now possible to explore the chronology and temporality of the megalithic phenomenon of south-eastern Iberia. Ninety new dates have been obtained based on human bone samples selected according to the minimum number of individuals identified in each tomb. Four main conclusions can be drawn from this radiocarbon series modelled in a Bayesian framework: i) the funerary rituals span a very long period that began in 3810–3635 cal BC and ended in 425–690 cal AD, although the mortuary activity was far less intense from the end of the second millennium; ii) the tombs were built at different times and used on different temporal scales, ranging from a few decades to several centuries; iii) although there is a clear chronological sequence between the tholoi and the other types of tomb, all were contemporaneous during the 3rd millennium, coinciding with their peak mortuary activity; and iv) the continuity of mortuary practices reached an unexpected importance during the Bronze Age, mainly in the tholos-type tombs.

Impact response and energy absorption of human skull cellular bones.

A skull fracture, due to a composition of typical lightweight cellular structures, is the most common type of traumatic brain injury. This paper presents a systematic investigation on the failure mechanism and energy absorption of skull cellular bones under low- and medium-velocity impact loadings. Non-destructive three-dimensional micro-computed tomography (Micro-CT) is utilized to scan samples of human skull cellular bones, and relevant structural parameters are obtained to reconstruct a finite element (FE) model of these bones. Micro-structures, mechanical properties, and failure process analysis of human skull cellular bones under impact loadings are investigated. The effects of some typical parameters, such as impact velocity and angle, impactor shape and density, and various reconstructed sections on the impact behavior of human skull cellular bones are investigated. Their impact properties and energy absorption are summarized. The present work will be of great significance in understanding the mechanical mystery of human skull cellular bones under impact loading.