Hydrolytic Damage Research Articles

Degradation behavior and ageing mechanism of E-glass fiber reinforced epoxy resin composite pipes under accelerated thermal ageing conditions

In this work, accelerated ageing experiments with circulating air and simulated oilfield water were carried out at 95 °C on aromatic amine-cured GFRP pipes used in oilfield environments, with effective ageing times of 5000 h and 3000 h respectively. The differences in ageing behavior and ageing mechanisms of the GFRP tubes at different times under the two conditions were then analyzed and discussed. The changes in the apparent morphology and microstructure of the samples after thermal ageing were first observed using optical microscopy and scanning electron microscopy, and the results demonstrated that the thermal oxygen environment triggered more drastic color changes and obvious oxidation layers. The resin matrix manifests a large number of nano-scale micropores and modest matrix shrinkage pores in the micron size range, this is accompanied by damage to the fiber cross-section. Hydrothermal ageing causes further dissolution of the surface resin and dissolution of the exposed fibers. ATR-FTIR analysis verifies the increase in CO bonding of the ester group during thermal oxidation and the decreasing strength of the C–O–C and C–H bonds, while the behavior of ageing water absorption and glass fiber hydrolysis is illustrated by changes in the intensity of the –OH and Si–O characteristic bands. NMR hydrogen spectroscopy verified the formation of amides, methyl ethers and carboxylic acids in the thermal oxidation products of epoxy resins. Furthermore, the decay pattern of the circumferential tensile strength indicates that the hydrothermal environment has a more significant effect on the mechanical properties of GFRP pipes, which is attributed to the physical dissolution of the surface resin, significant hydrolytic damage to the surface exposed fibers, and the combined damage to the resin-fiber interfacial bonding by chloride ions in simulated oilfield water.

Electrochemical impedance characteristics and degradation behaviors of carbon fiber reinforced composite attacked by HF solution

PurposeThe purpose of this study is to ensure the safe use of carbon fiber composite pressure vessels in the nuclear industry environment.Design/methodology/approachThis study investigated the degradation behaviors of carbon fiber reinforced composite (CFRP) using the specific corrosive media HF solution, with a focus on the damage to the surface epoxy layer. The degradation behaviors of CFRP in HF solution were examined by electrochemical methods and surface characterization, using HCl, NaCl and NaF solution for comparison.FindingsThe results showed that the specimen in HF solution will have a value of |Z|0.01 Hz one order of magnitude lower, a substantially lower contact angle, more breakage of the surface epoxy and the stronger O─H peak and weaker C─O─C peak in the Fourier transform infrared spectrum, indicating severe hydrolytic damage to the surface epoxy.Originality/valueThe work focuses on the degradation damage to CFRP surface epoxy by specific corrosive media HF.

Numerical Approach to Simulate the Mechanical Behavior of Biodegradable Polymers during Erosion.

Biodegradable polymers find applications in many market segments. The ability to meet mechanical requirements within a certain time range, after which it degrades and is naturally absorbed, can be used to produce short-term use products that can be easily disposable with less environmental impact. In the segment of medical devices used in regenerative medicine, these materials are used to produce temporary implants that are naturally assimilated by the human body, avoiding a removal surgery. However, the design of these temporary devices still presents great challenges, namely in the verification of the main requirement: the lifetime of the device, associated with the progressive loss of mechanical properties, until its complete erosion and assimilation. Thus, in this study, a numerical approach is proposed to simulate the polymeric device's mechanical behavior during its hydrolytic degradation by combining the hydrolysis kinetics, that depends on mechanical factors and promotes a decrease of molecular weight and consequent decrease of mechanical performance, and erosion, when molecular weight reaches a threshold value and the polymer becomes soluble and diffuses outward, resulting in mass loss and decreasing cross-sectional area, which also contributes to the mechanical performance reduction of the device. A phenomenological approach, using the combination of continuum-based hydrolytic damage for the evolution of mechanical properties that depends on the stress field and further removal of the degraded element (to simulate mass loss) was used. Both elastoplastic and hyperelastic constitutive models were applied on this study, where the material model parameters locally depend on the molecular weight.

Research of changes in quality indicators of fish pate with non-traditional raw materials

Taking into account the results of literature research on the nutritional value of quail eggs, it was found that the development of technology of fish pates with their use is relevant and has practical significance in the technology of production of fish products. The article presents the results of chemical composition, organoleptic evaluation and physico-chemical changes of fish pate with the addition of non-traditional raw materials and setting their shelf life. The expediency of combining freshwater fish with plant and animal raw materials to expand the range of biologically valuable food products is shown. Positive general impressions, harmonious, fishy and sweet-salty taste, showed the feasibility of combining quail eggs and vegetable raw materials with freshwater fish, as evidenced by high performance in appearance, taste and smell. According to the consistency of fish pate smeared and quite dense. It was found that in the experimental sample during storage are hydrolytic spoilage, which indicates the intensive hydrolysis of lipids and the accumulation of free fatty acids in these samples. In the prototypes, the hydrolytic damage gradually increases and only reaches the critical point by the end of the shelf life. Oxidative processes in the lipids of fish pastes were studied by changes in the accumulation of primary oxidation products – peroxides and secondary products – carbonyl compounds. According to the dynamics of changes in the peroxide content of lipids in pate, it was found that the control sample is not subject to storage for 5 days as well as the test sample, the fat content deteriorates and is characterized as non-storage. It has been experimentally established that the addition of non-traditional raw materials allows not only to improve the technology of pate production, but also to solve the problem of obtaining a product of high nutritional value. The authors found that the developed technology of fish pate will significantly expand the range of functional products based on natural ingredients, which will to some extent expand the current problem of processing raw materials in inland waters of Ukraine.

Research on changes of the quality indicators of semi-finished products during during storage

Considering the results of literary studies on the nutritional value and biological efficiency of cranberries and goji berries, it has been established that the development of the technology of semi-finished minced products with their use is relevant and has practical importance in the production of fish products. The article deals with the results of the chemical composition, organoleptic evaluation, and physical and chemical changes in semi-finished minced products with the addition of non-traditional raw materials and the establishment of their shelf life. The expediency of combining freshwater fish with plant material to expand the range of biologically valuable food products is presented in the article. The general positive impressions, harmonious, fish and sweet-salty taste, have shown the expediency of combining cranberries and goji berries with freshwater fish, as evidenced by high levels of appearance, taste, and smell. In terms of consistency, fish cutlets are plastic and dense on the cut. It has been found that there are processes of hydrolytic damage in the control sample after 90 days of storage, which indicates the intensive lipid hydrolysis and the accumulation of free fatty acids in these samples. In experimental samples, hydrolytic damage gradually increases and reaches its critical point only close to the end of the shelf life. Oxidation processes in the lipids of semi-finished products were studied by changes in the accumulation of primary oxidation products – peroxides and secondary products – carbonyl compounds. According to the dynamics of changes in the peroxide value of lipids of semi-finished products, it has been established that the control sample for 60-135 days has not been subjected to storage, and in experimental samples after 135 days, the quality of the fat deteriorates and is characterized as the one that is not subjected to storage. The research has established that the use of non-traditional raw materials in the production of semi-finished minced products allows to improve the technology of production and solve the problem of obtaining the product of a high nutritional value. The authors found that the developed technology of production of semi-finished fish products will significantly expand the range of products of functional purpose based on natural components, which will allow, to some extent, to broaden the current problem of processing raw materials from domestic reservoirs in Ukraine.

Freeze-drying improves DNA yield from teeth

The common method of preparing teeth prior to DNA extraction involves cleaning, decontamination, drying and pulverisation. Moisture in post-mortem teeth can promote bacterial growth and hydrolytic damage that could contribute to DNA degradation, whilst also possibly reducing the efficiency of sample pulverisation and DNA release. Here we compared DNA extraction from pig teeth, with- and without freeze-drying, to examine the impact of removing moisture on DNA yield. Quantitative real-time polymerase chain reaction (qPCR) was used to quantify an 83 bp mitochondrial DNA fragment and two nuclear DNA fragments of 82 bp and 150 bp. The comparative results showed that sample preparation with freeze-drying resulted in a higher DNA yield without compromising the DNA quality. This study highlights the advantage of incorporating a freeze-drying to improve the DNA yield and minimising the loss of DNA during sample preparation of teeth.

Mechanical characterization of hydrolysis effects on the stiffness of bioabsorbable polymeric filaments: An experimental and modeling approach based on a simple constitutive damage model

This manuscript presents an experimental and modeling approach in order to characterize the stiffness loss of bioabsorbable polymer filaments due to hydrolysis. In this regard, bioabsorbable suture yarns (poly(lactic-co-glycolic) acid—PLGA) were chosen as a representative material for the present investigation. The observed mechanical response was characterized by means of a thermodynamically consistent constitutive variational framework. Usually, two different damage variables are assumed to take place in this class of materials: a hydrolytic damage (long-term degradation) and a strain-driven damage (short-term degradation). This work concerns the proposition of a constitutive model that only considers the hydrolytic damage, in which a specific strain energy and a proper dissipation damage potential were tailored to model the tested material. A nonlinear curve fitting procedure based on Particle Swarm Optimization was performed to identify the constitutive parameters. A set of numerical simulations demonstrates the effectiveness of the proposed constitutive model to predict damage-induced creep and damage-induced stress relaxation, behaviors that can be used as design criteria in absorbable implants. The main achieved results show that the proposed constitutive approach leads to a simple but effective model capable to drive the first steps in the design of absorbable biomedical devices. The present variational framework can be extended to study the constitutive response of other bioabsorbable polymers, accounting for viscous and/or plastic behaviors.

Numerical approach to simulate the mechanical behavior of biodegradable structures considering degradation time and heterogeneous stress field

AbstractBiodegradable polymers are widely used to manufacture biodegradable devices, such as those used in regenerative medicine. In many cases, nonuniform degradation can arise from nonuniform stress fields. The developed numerical methodology can simulate the mechanical behavior of three‐dimensional structures subjected to loads during degradation after a given degradation time, thus providing a valuable tool for pre validation of biodegradable devices. Degradation rate was assumed as linear function of the local von Mises stress. Material model parameters change as degradation proceeds and hydrolytic damage increases. Hence, shear modulus of the neo‐Hookean constitutive model was assumed as linear function of hydrolytic damage. The methodology was developed in a finite elements' framework using ABAQUS/Standard. The local hydrolytic damage and the consequent shear modulus evolutions were calculated by means of a user material subroutine. The stress field affects locally the kinetics of degradation and the evolution of hydrolytic damage. Thus, local hydrolytic damage and the material parameter are updated at each time step to recalculate stress and strain fields at the inputted degradation time. The aim of this work was to allow the simulation of biodegradable devices subjected to both mechanical and chemical environments.

Preparation and characterization of proton exchange polyvinylidene fluoride membranes incorporated with sulfonated mesoporous carbon/SPEEK nanocomposite

Sulfonation of mesoporous carbon CMK-3 (sCMK-3) prepared by nano-casting technique was carried out post synthesis using one-step process. The incorporation of the acid groups was confirmed using XRD, Raman spectroscopy, FTIR, SEM, TEM and BET isotherm. The sCMK-3 was incorporated into sulfonated poly(ether ether ketone) to form a nanocomposite which was introduced into polyvinylidene fluoride matrix to form a proton exchange membrane. The physicochemical characteristics of the nanocomposite incorporated membranes were characterized using FTIR, ionic exchange capacity, water uptake, swelling ratio, mechanical stability and TGA. The nanocomposite incorporated membranes showed greater surface wettability and higher ion-exchange capacity. The presence of the –SO3H acid groups plays a major role in improving the proton conductivity through the Grotthuss-type mechanism. M4 membrane was identified to be a suitable replacement in the DMFC as it had sufficiently high tensile strength (862.2 MPa), high proton conductivity (0.081 S cm−1) at 45 °C and ultra-low methanol permeability (2.17 × 10−8 cm2 s−1). No evident hydrolytic damage could be identified and had sufficiently high thermal stability and hence can be proposed as a suitable alternative for Nafion membranes in high temperature, low humidity DMFC applications.

A multi-physics constitutive model to predict hydrolytic aging in quasi-static behaviour of thin cross-linked polymers

The effect of hydrolytic aging on mechanical quasi-static responses of rubber-like materials, in particular, the idealized Mullins effect and permanent set have been modeled. The effect of hydrolytic damage on the mechanical integrity of the polymer matrix is modeled as the direct competition of two micro-structural phenomena (i) chain scission and (ii) reduction of cross-links. Both phenomena and their correlation were modeled and thus, the strain energy of the polymer matrix is written with respect to three independent mechanisms; i) the shrinking original matrix that has not been attacked by water, ii) conversion of the first network to a new network due to the reduction of the cross-links, and iii) energy loss from network degradation due to water attacks to polymer active agents. The proposed model satisfies the Clausius-Duhem inequality and is thus physically feasible. The model is validated with respect to sets of our experimental data and other sets available in the literature. The proposed model is based on the assumption of homogeneous diffusion and mainly relevant for thin samples. In view of its accuracy, interpret-ability, and deep insight it provides into the nature of damage accumulation, the model is a good choice for further implementation in FE applications.

Crystalline Polymers Based on Dative Boron–Nitrogen Bonds and the Quest for Porosity

Crystalline networks based on dative boron–nitrogen bonds were obtained by combining polytopic N-donor ligands with polyboronic esters. The utilization of a tetrahedral boronate ester gave rise to a sheet structure, whereas either a linear polymer or a diamond-like network was observed for a tetrahedral N-donor ligand. The intrinsic flexibility of B←N linkages favors tight intermolecular packing and interpenetration in the crystalline state. Amorphous B←N networks, on the other hand, were found to possess porosity with BET surface areas of up to ∼300 m2 g–1. These materials display processability in organic solvents, and hydrolytic damage can be repaired by simple heating-cooling cycles.

Research on changes of the quality indicators of semi-finished of dietary minced products during their storage

Taking into account the results of literary studies on the nutritional value and biological efficiency of flaxseeds and chia seeds, it has been established that the development of the technology of semi-finished minced products with their use is relevant and has a practical importance in the production of fish products. The article deals with the results of the chemical composition, organoleptic evaluation and physical and chemical changes in semi-finished minced products with the addition of non-traditional raw materials and the establishment of their storage time. The expediency of combining a freshwater fish with plant material to expand the range of biologically valuable food products is presented in the article. The general positive impressions, harmonious, fish and sweet-salty taste, have shown the expediency of combining flaxseed and chia seeds with freshwater fish, as evidenced by high levels of appearance, taste and smell. In terms of consistency, fish cutlets are plastic and dense on the cut. It has been found, that there are processes of hydrolytic damage in the control sample after 90 days of storage, which indicates the intensive lipid hydrolysis and the accumulation of free fatty acids in these samples. In experimental samples a hydrolytic damage gradually increases, and reaches its critical point only close to the end of the storage time. The oxidation processes in the lipids of semi-finished products were studied by changes in the accumulation of primary oxidation products – peroxides and secondary products – carbonyl compounds. According to the dynamics of changes in the peroxide value of lipids of semi-finished products, it has been established that the control sample for 60–135 days has not been subjected to storage, and in experimental samples after 135 days, the quality of the fat deteriorates and is characterized as the one that is not subjected to storage. The research has established that the use of non-traditional raw materials in a production of semi-finished minced products allows not only to improve the technology of production, but also to solve the problem of obtaining the product of a high nutritional value. The authors found that the developed technology of production of semi-finished fish products will significantly expand the range of products of functional purpose based on natural components, which will allow, to some extent, to expand the actual problem of processing raw materials from domestic reservoirs in Ukraine.

Squeezing water from a stone: high-throughput sequencing from a 145-year old holotype resolves (barely) a cryptic species problem in flying lizards

We used Massively Parallel High-Throughput Sequencing to obtain genetic data from a 145-year old holotype specimen of the flying lizard, Draco cristatellus. Obtaining genetic data from this holotype was necessary to resolve an otherwise intractable taxonomic problem involving the status of this species relative to closely related sympatric Draco species that cannot otherwise be distinguished from one another on the basis of museum specimens. Initial analyses suggested that the DNA present in the holotype sample was so degraded as to be unusable for sequencing. However, we used a specialized extraction procedure developed for highly degraded ancient DNA samples and MiSeq shotgun sequencing to obtain just enough low-coverage mitochondrial DNA (721 base pairs) to conclusively resolve the species status of the holotype as well as a second known specimen of this species. The holotype was prepared before the advent of formalin-fixation and therefore was most likely originally fixed with ethanol and never exposed to formalin. Whereas conventional wisdom suggests that formalin-fixed samples should be the most challenging for DNA sequencing, we propose that evaporation during long-term alcohol storage and consequent water-exposure may subject older ethanol-fixed museum specimens to hydrolytic damage. If so, this may pose an even greater challenge for sequencing efforts involving historical samples.

Anomalous aging of EPDM and FEPM under combined thermo-oxidative and hydrolytic conditions

Previous observation of EPDM and FEPM materials aged in thermo-oxidative and thermo-oxidative plus hydrolytic environments revealed an unusual trend: the degradation and disintegration of these polymers in the former case but the ability to maintain mechanical performance and shape in the latter [1]. No abnormalities were observed in the chemical (oxidation rates, FTIR spectra, solvent uptake, gel content, and weight loss vs. temperature) or physical (modulus profile) measurements that could explain these empirically observed aging differences. A second controlled aging test was conducted to verify this trend using only EPDM. Once again it was shown that thermo-oxidative conditions appear to cause more degradative damage (enhanced embrittlement) than observed for the combined thermo-oxidative plus hydrolytic environments. From these data we conclude that water may favorably interfere with normal thermo-oxidative degradation processes. This interference may occur via some combination of chemical and physical property changes in the presence of steam such as: oxidation rate and O2 permeability changes, additional sensitivity to hydrolytic damage, and/or mechanistic changes in relation to pH and hydroperoxide formation.

Coupled ductile–hydrolytic damage model based on variational constitutive updates

This work presents a constitutive model suitable for the description of materials showing elastic–viscoplastic behavior and coupled ductile–hydrolytic damage. Such behavior is frequently observed in bioabsorbable materials that have been increasingly used in the development of medical implants (surgical sutures, screws, plates, anchors, stents, etc.). An approach for describing this coupling between mechanical and hydrolytic damage is the core and main contribution of the current proposal. The model is embedded within a variational framework in such a way that the update of internal variables is driven by a minimization principle. A complete description of the model is presented as well as operational details related to an incremental algorithm suitable for finite element calculations. Despite the complexity of the phenomena involved in the formulation, it is shown that the update algorithm follows a simple operational scheme. Several numerical tests were carried out at a material point level, showing the model capability to handle coupling effects of ductile and chemical (hydrolytic) damage. Furthermore, some implications related to the dependence of dissipation functions on state variables, mainly those dependent on the elastic state, were analyzed demonstrating the possible consequences on the solution of damage and stress. The material model was successfully implemented in an in-house code and a commercial code, where examples of application on 3D devices were run bringing insight into realistic applications of the proposed model.

Considering DNA damage when interpreting mtDNA heteroplasmy in deep sequencing data

Resolution of mitochondrial (mt) DNA heteroplasmy is now possible when applying a massively parallel sequencing (MPS) approach, including minor components down to 1%. However, reporting thresholds and interpretation criteria will need to be established for calling heteroplasmic variants that address a number of important topics, one of which is DNA damage. We assessed the impact of increasing amounts of DNA damage on the interpretation of minor component sequence variants in the mtDNA control region, including low-level mixed sites. A passive approach was used to evaluate the impact of storage conditions, and an active approach was employed to accelerate the process of hydrolytic damage (for example, replication errors associated with depurination events). The patterns of damage were compared and assessed in relation to damage typically encountered in poor quality samples. As expected, the number of miscoding lesions increased as conditions worsened. Single nucleotide polymorphisms (SNPs) associated with miscoding lesions were indistinguishable from innate heteroplasmy and were most often observed as 1–2% of the total sequencing reads. Numerous examples of miscoding lesions above 2% were identified, including two complete changes in the nucleotide sequence, presenting a challenge when assessing the placement of reporting thresholds for heteroplasmy. To mitigate the impact, replication of miscoding lesions was not observed in stored samples, and was rarely seen in data associated with accelerated hydrolysis. In addition, a significant decrease in the expected transition:transversion ratio was observed, providing a useful tool for predicting the presence of damage-induced lesions. The results of this study directly impact MPS analysis of minor sequence variants from poorly preserved DNA extracts, and when biological samples have been exposed to agents that induce DNA damage. These findings are particularly relevant to clinical and forensic investigations.

Ancient DNA and the tropics: a rodent's tale.

Most genetic studies of Holocene fauna have been performed with ancient samples from dry and cold regions, in which preservation of fossils is facilitated and molecular damage is reduced. Ancient DNA work from tropical regions has been precluded owing to factors that limit DNA preservation (e.g. temperature, hydrolytic damage). We analysed ancient DNA from rodent jawbones identified as Ototylomys phyllotis, found in Holocene and Late Pleistocene stratigraphic layers from Loltún, a humid tropical cave located in the Yucatan peninsula. We extracted DNA and amplified six short overlapping fragments of the cytochrome b gene, totalling 666 bp, which represents an unprecedented success considering tropical ancient DNA samples. We performed genetic, phylogenetic and divergence time analyses, combining sequences from ancient and modern O. phyllotis, in order to assess the ancestry of the Loltún samples. Results show that all ancient samples fall into a unique clade that diverged prior to the divergence of the modern O. phyllotis, supporting it as a distinct Pleistocene form of the Ototylomys genus. Hence, this rodent's tale suggests that the sister group to modern O. phyllotis arose during the Miocene-Pliocene, diversified during the Pleistocene and went extinct in the Holocene.

Deterioration of ancient Korean paper (Hanji), treated with beeswax: A mechanistic study

In the early 15th century, beeswax coating was applied to some of the cellulosic documents in a futile attempt to better conserve the paper. However, this treatment caused much more severe degradation compared to untreated Hanji. In the current study, the degradation pathway of this beeswax-treated Hanji has been clarified for the first time. The degradation of cellulose was investigated by labeling of oxidized groups combined with gel permeation chromatography, providing profiles of carbonyl and carboxyl groups relative to the molar mass distribution. The beeswax caused purely hydrolytic damage, leading to a decrease in molar mass to about one fifth of the original value. Oxidative degradation, by contrast, did not occur to any significant extent. Hydrolysis was not caused by acids but by microorganism feeding on the beeswax and excreting cellulolytic enzymes, which cause similar cellulose damage patterns. The hydrolytic enzymes were identified by typical metabolites present in the Hanji.

Abstract A168: Quantitative high-throughput screening for inhibitors of human apurinic/apyrimidinic endonuclease APE1

Abstract The major human apurinic/apyrimidinic endonuclease APE1 plays a pivotal role in the repair of spontaneous hydrolytic, oxidative, and non-enzymatic alkylation base damage via the DNA base excision repair (BER) pathway. The increased activity of APE1, often observed in tumor cells, is thought to contribute to the development of resistance to various anticancer drugs; conversely, its down-regulation sensitizes tumor cells to DNA damaging agents via induction of apoptosis. Therefore, inhibiting APE1 within the BER pathway in cancer cells is an attractive strategy in the attempts to overcome chemotherapeutic resistance. Despite ongoing efforts, potent specific inhibitors of APE1 have yet to be discovered. We developed a fluorogenic substrate operating in the red-shifted fluorescence spectral region to configure a highly robust kinetic assay for use in 1536-well based automated high-throughput screening (HTS). The assay was used in a titration-based screen of the LOPAC1280 library to identify potential APE1 inhibitors which were further validated and profiled in a panel of assays including radiotracer-based incision assay, Thiazole Orange fluorophore displacement test for promiscuous DNA binders, and E. coli Endo IV counterscreen. Select compounds which passed the above validation steps were progressed to studies of increased biochemical complexity and were shown to inhibit abasic-site incision activity in whole cell protein extracts and to potentiate the genotoxic effect of methyl methanesulfonate (MMS), consistent with suppression of BER on a cellular level. Subsequently, a fully automated HTS was conducted against a collection of 241,291 diverse compounds tested as 7-concentration series at a 4 uL reaction volume in 1536-well plate format. To our knowledge, this represents the first large-scale HTS to identify inhibitors of APE1, and provides a key first step in the development of novel agents targeting BER for cancer treatment. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A168.

Postmortem Miscoding Lesions in Sequence Analysis of Human Ancient Mitochondrial DNA

Genetic miscoding lesions can cause inaccuracies during the interpretation of ancient DNA sequence data. In this study, genetic miscoding lesions were identified and assessed by cloning and direct sequencing of degraded, amplified mitochondrial DNA (mtDNA) extracted from human remains. Forty-two individuals, comprising nine collections from five geographic locations, were analyzed for the presence of DNA damage that can affect the generation of a correct mtDNA profile. In agreement with previous studies, high levels (56.5% of all damage sites) of proposed hydrolytic damage products were observed. Among these, type 2 transitions (cytosine --> thymine or guanine --> adenine), which are highly indicative of hydrolytic deamination, were observed in 50% of all misincorporations that occurred. In addition to hydrolytic damage products, oxidative damage products were also observed in this study and were responsible for approximately 43.5% of all misincorporations. This level of misincorporation is in contrast to previous studies characterizing miscoding lesions from the analysis of bone and teeth, where few to no oxidative damage products were observed. Of all the oxidative damage products found in this study, type 2 transversions (cytosine --> adenine/guanine --> thymine or cytosine --> guanine/guanine --> cytosine), which are commonly formed through the generation of 8-hydroxyguanine, accounted for 30.3% of all genetic miscoding lesions observed. This study identifies the previously unreported presence of oxidative DNA damage and proposes that damage to degraded DNA templates is highly specific in type, correlating with the geographic location and the taphonomic conditions of the depositional environment from which the remains are recovered.