Browsing by Subject "DIFFUSION"

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  • Barmaki, Samineh; Obermaier, Daniela; Kankuri, Esko; Vuola, Jyrki; Franssila, Sami; jokinen, Ville (2020)
    A hypoxic (low oxygen level) microenvironment and nitric oxide paracrine signaling play important roles in the control of both biological and pathological cell responses. In this study, we present a microfluidic chip architecture for nitric oxide delivery under a hypoxic microenvironment in human embryonic kidney cells (HEK-293). The chip utilizes two separate, but interdigitated microfluidic channels. The hypoxic microenvironment was created by sodium sulfite as the oxygen scavenger in one of the channels. The nitric oxide microenvironment was created by sodium nitroprusside as the light-activated nitric oxide donor in the other channel. The solutions are separated from the cell culture by a 30 µm thick gas-permeable, but liquid-impermeable polydimethylsiloxane membrane. We show that the architecture is preliminarily feasible to define the gaseous microenvironment of a cell culture in the 100 µm and 1 mm length scales.
  • Zhang, Chao; Vehkamäki, Marko; Pietikäinen, Mika; Leskelä, Markku; Ritala, Mikko (2020)
    Novel area-selective molecular layer deposition (AS-MLD) of polyimide (PI) on Cu versus native SiO2 was studied. By use of 1,6-diaminohexane (DAH) and pyromellitic dianhydride (PMDA) as precursors, PI films can be selectively deposited on the Cu surface at 200-210 degrees C with a rate around 7.8 A/cycle while negligible growth takes place on SiO2. The selectivity was successfully demonstrated also on Cu/SiO2 patterns at 200 degrees C; after 180 MLD cycles, around 140 nm thick PI was deposited on Cu regions while
  • Mason, D. R.; Sand, A. E.; Dudarev, S. L. (2019)
    We describe the development of a new object kinetic Monte Carlo (kMC) code where the elementary defect objects are off-lattice atomistic configurations. Atomic-level transitions are used to transform and translate objects, to split objects and to merge them together. This gradually constructs a database of atomic configurations-a set of relevant defect objects and their possible events generated on-the-fly. Elastic interactions are handled within objects with empirical potentials at short distances, and between spatially distinct objects using the dipole tensor formalism. The model is shown to evolve mobile interstitial clusters in tungsten faster than an equivalent molecular dynamics (MD) simulation, even at elevated temperatures. We apply the model to the evolution of complex defects generated using MD simulations of primary radiation damage in tungsten. We show that we can evolve defect structures formed in cascade simulations to experimentally observable timescales of seconds while retaining atomistic detail. We conclude that the first few nanoseconds of simulation following cascade initiation would be better performed using MD, as this will capture some of the near-temperature-independent evolution of small highly-mobile interstitial clusters. For the 20keV cascade annealing simulations considered here, we observe internal relaxations of sessile objects. These relaxations would be difficult to capture using conventional object kMC, yet are important as they establish the conditions for long timescale evolution.
  • Kindler, Oliver; Pulkkinen, Otto; Cherstvy, Andrey G.; Metzler, Ralf (2019)
    Quorum-sensing bacteria in a growing colony of cells send out signalling molecules (so-called "autoinducers") and themselves sense the autoinducer concentration in their vicinity. Once-due to increased local cell density inside a "cluster" of the growing colony-the concentration of autoinducers exceeds a threshold value, cells in this clusters get "induced" into a communal, multi-cell biofilm-forming mode in a cluster-wide burst event. We analyse quantitatively the influence of spatial disorder, the local heterogeneity of the spatial distribution of cells in the colony, and additional physical parameters such as the autoinducer signal range on the induction dynamics of the cell colony. Spatial inhomogeneity with higher local cell concentrations in clusters leads to earlier but more localised induction events, while homogeneous distributions lead to comparatively delayed but more concerted induction of the cell colony, and, thus, a behaviour close to the mean-field dynamics. We quantify the induction dynamics with quantifiers such as the time series of induction events and burst sizes, the grouping into induction families, and the mean autoinducer concentration levels. Consequences for different scenarios of biofilm growth are discussed, providing possible cues for biofilm control in both health care and biotechnology.
  • Hurmekoski, Elias; Sjolie, Hanne K. (2018)
    Scenario analyses are widely used in forest sector foresight studies, being typically based on either qualitative or quantitative approaches. As scenario analyses are used for informing decision-makers, it is of interest to contrast the similarities and differences between the scenario processes and outcomes using quantitative and qualitative approaches and to explore the underlying causes of differences. This paper uses the output from a qualitative scenario study to design forest sector model (FSM) scenarios and compares the results from the two approaches. We analyse two cases on wood products markets in Norway: i) Wood products suppliers establish a developer firm specializing on wood construction to boost demand, and ii) Levying a carbon tax while reducing CO2 emissions in cement production. Comparing the qualitative studies (innovation diffusion analysis, backcasting and Delphi) and FSM analyses (NorFor model), the results resemble for case ii) but deviate strongly for case i). Notably, the strategy aiming to boost the demand for domestic wood products leads in NorFor mainly to an increase in imports with limited impact on Norwegian sawnwood production. Causes of the discrepancies are discussed. Despite the challenges of combining the two frameworks, we believe that the method where assumptions based on stakeholder input or other qualitative research approaches are elaborated in a FSM and compared, should be more explored. Importantly, applying various methods and frameworks allows for complementing and diversifying the picture, and thus improving the knowledge base. (C) 2017 Department of Forest Economics, Swedish University of Agricultural Sciences, Umea. Published by Elsevier GmbH.
  • MRI-GENIE & GISCOME Investigators; Int Stroke Genetics Consortium; Bonkhoff, Anna K.; Ullberg, Teresa; Bretzner, Martin; Strbian, Daniel; Tatlisumak, Turgut (2022)
    Background purposeA substantial number of patients with acute ischemic stroke (AIS) experience multiple acute lesions (MAL). We here aimed to scrutinize MAL in a large radiologically deep-phenotyped cohort. Materials and methodsAnalyses relied upon imaging and clinical data from the international MRI-GENIE study. Imaging data comprised both Fluid-attenuated inversion recovery (FLAIR) for white matter hyperintensity (WMH) burden estimation and diffusion-weighted imaging (DWI) sequences for the assessment of acute stroke lesions. The initial step featured the systematic evaluation of occurrences of MAL within one and several vascular supply territories. Associations between MAL and important imaging and clinical characteristics were subsequently determined. The interaction effect between single and multiple lesion status and lesion volume was estimated by means of Bayesian hierarchical regression modeling for both stroke severity and functional outcome. ResultsWe analyzed 2,466 patients (age = 63.4 +/- 14.8, 39% women), 49.7% of which presented with a single lesion. Another 37.4% experienced MAL in a single vascular territory, while 12.9% featured lesions in multiple vascular territories. Within most territories, MAL occurred as frequently as single lesions (ratio similar to 1:1). Only the brainstem region comprised fewer patients with MAL (ratio 1:4). Patients with MAL presented with a significantly higher lesion volume and acute NIHSS (7.7 vs. 1.7 ml and 4 vs. 3, p(FDR) < 0.001). In contrast, patients with a single lesion were characterized by a significantly higher WMH burden (6.1 vs. 5.3 ml, p(FDR) = 0.048). Functional outcome did not differ significantly between patients with single versus multiple lesions. Bayesian analyses suggested that the association between lesion volume and stroke severity between single and multiple lesions was the same in case of anterior circulation stroke. In case of posterior circulation stroke, lesion volume was linked to a higher NIHSS only among those with MAL. ConclusionMultiple lesions, especially those within one vascular territory, occurred more frequently than previously reported. Overall, multiple lesions were distinctly linked to a higher acute stroke severity, a higher total DWI lesion volume and a lower WMH lesion volume. In posterior circulation stroke, lesion volume was linked to a higher stroke severity in multiple lesions only.
  • Drago, Salvatore E.; Craparo, Emanuela F.; Luxenhofer, Robert; Cavallaro, Gennara (2021)
    In this paper, two amphiphilic graft copolymers were synthesized by grafting polylactic acid (PLA) as hydrophobic chain and poly(2-methyl-2-oxazoline) (PMeOx) or poly(2-methyl-2-oxazine) (PMeOzi) as hydrophilic chain, respectively, to a backbone of α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA). These original graft copolymers were used to prepare nanoparticles delivering Zileuton in inhalation therapy. Among various tested methods, direct nanoprecipitation proved to be the best technique to prepare nanoparticles with the smallest dimensions, the narrowest dimensional distribution and a spherical shape. To overcome the size limitations for administration by inhalation, the nano-into-micro strategy was applied, encapsulating the nanoparticles in water-soluble mannitol-based microparticles by spray-drying. This process has allowed to produce spherical microparticles with the proper size for optimal lung deposition, and, once in contact with fluids mimicking the lung district, able to dissolve and release non-aggregated nanoparticles, potentially able to spread through the mucus, releasing about 70% of the drug payload in 24hours.
  • Chetrite, Raphael; Muratore-Ginanneschi, Paolo; Schwieger, Kay (2021)
    We present an english translation of Erwin Schrödinger's paper on "On the Reversal of the Laws of Nature". In this paper Schrödinger analyses the idea of time reversal of a diffusion process. Schrödinger's paper acted as a prominent source of inspiration for the works of Bernstein on reciprocal processes and of Kolmogorov on time reversal properties of Markov processes and detailed balance. The ideas outlined by Schrödinger also inspired the development of probabilistic interpretations of quantum mechanics by Fényes, Nelson and others as well as the notion of "Euclidean Quantum Mechanics" as probabilistic analogue of quantization. In the second part of the paper Schrödinger discusses the relation between time reversal and statistical laws of physics. We emphasize in our commentary the relevance of Schrödinger's intuitions for contemporary developments instatistical nano-physics.
  • Boi, S. (2019)
    The Maxey-Riley equation and its simplified versions represent the most widespread tool to investigate dynamics and dispersion of inertial small particles in turbulent flows. The numerical solution of such models is often very challenging, and some of their terms, such as the molecular diffusivity or the Basset history force, are often neglected to reduce the complexity upon suitable approximations. Here, we propose exact results with regard to the rate of transport on large time scales in random shear flows. These can be expediently used as a benchmark to develop and assess algorithms when solving this class of stochastic integrodifferential problems on large time scales.
  • Lamminsalo, Marko; Karvinen, Timo; Subrizi, Astrid; Urtti, Arto; Ranta, Veli-Pekka (2020)
    Purpose To estimate the diffusion coefficients of an IgG antibody (150 kDa) and its antigen-binding fragment (Fab; 50 kDa) in the neural retina (D-ret) and the combined retinal pigment epithelium-choroid (DRPE-cho) with a 3-dimensional (3D) ocular pharmacokinetic (PK) model of the rabbit eye. Methods Vitreous, retina, and aqueous humor concentrations of IgG and Fab after intravitreal injection in rabbits were taken from Gadkar et al. (2015). A least-squares method was used to estimate D(ret)and D(RPE-cho)with the 3D finite element model where mass transport was defined with diffusion and convection. Different intraocular pressures (IOP), initial distribution volumes (V-init), and neural retina/vitreous partition coefficients (K-ret/vit) were tested. Sensitivity analysis was performed for the final model. Results With the final IgG model (IOP 10.1 Torr, V(init)400 mu l, K(ret/vit)0.5), the estimated D(ret)and D(RPE-cho)were 36.8 x 10(-9)cm(2)s(-1)and 4.11 x 10(-9)cm(2)s(-1), respectively, and 76% of the dose was eliminated via the anterior chamber. Modeling of Fab revealed that a physiological model parameter "aqueous humor formation rate" sets constraints that need to be considered in the parameter estimation. Conclusions This study extends the use of 3D ocular PK models for parameter estimation using simultaneously macromolecule concentrations in three ocular tissues.
  • EXTEND Investigator; ECASS-4 Investigator; EPITHET Investigator; Campbell, Bruce C.; Ma, Henry; Curtze, Sami; Donnan, Geoffrey A.; Kaste, Markku (2019)
    Background Stroke thrombolysis with alteplase is currently recommended 0-4.5 h after stroke onset. We aimed to determine whether perfusion imaging can identify patients with salvageable brain tissue with symptoms 4.5 h or more from stroke onset or with symptoms on waking who might benefit from thrombolysis. Methods In this systematic review and meta-analysis of individual patient data, we searched PubMed for randomised trials published in English between Jan 1, 2006, and March 1, 2019. We also reviewed the reference list of a previous systematic review of thrombolysis and searched ClinicalTrials. gov for interventional studies of ischaemic stroke. Studies of alteplase versus placebo in patients (aged =18 years) with ischaemic stroke treated more than 4.5 h after onset, or with wake-up stroke, who were imaged with perfusion-diffusion MRI or CT perfusion were eligible for inclusion. The primary outcome was excellent functional outcome (modified Rankin Scale [mRS] score 0-1) at 3 months, adjusted for baseline age and clinical severity. Safety outcomes were death and symptomatic intracerebral haemorrhage. We calculated odds ratios, adjusted for baseline age and National Institutes of Health Stroke Scale score, using mixed-effects logistic regression models. This study is registered with PROSPERO, number CRD42019128036. Findings We identified three trials that met eligibility criteria: EXTEND, ECASS4-EXTEND, and EPITHET. Of the 414 patients included in the three trials, 213 (51%) were assigned to receive alteplase and 201 (49%) were assigned to receive placebo. Overall, 211 patients in the alteplase group and 199 patients in the placebo group had mRS assessment data at 3 months and thus were included in the analysis of the primary outcome. 76 (36%) of 211 patients in the alteplase group and 58 (29%) of 199 patients in the placebo group had achieved excellent functional outcome at 3 months (adjusted odds ratio [OR] 1.86, 95% CI 1.15-2.99, p=0.011). Symptomatic intracerebral haemorrhage was more common in the alteplase group than the placebo group (ten [5%] of 213 patients vs one [<1%] of 201 patients in the placebo group; adjusted OR 9.7, 95% CI 1.23-76.55, p=0.031). 29 (14%) of 213 patients in the alteplase group and 18 (9%) of 201 patients in the placebo group died (adjusted OR 1.55, 0.81-2.96, p=0.66). Interpretation Patients with ischaemic stroke 4.5-9 h from stroke onset or wake-up stroke with salvageable brain tissue who were treated with alteplase achieved better functional outcomes than did patients given placebo. The rate of symptomatic intracerebral haemorrhage was higher with alteplase, but this increase did not negate the overall net benefit of thrombolysis. Copyright (c) 2019 Elsevier Ltd. All rights reserved.
  • Franks, Victoria R.; Ewen, John G.; McCready, Mhairi; Thorogood, Rose (2020)
    Early independence from parents is a critical period where social information acquired vertically may become outdated, or conflict with new information. However, across natural populations, it is unclear if newly independent young persist in using information from parents, or if group-level effects of conformity override previous behaviours. Here, we test if wild juvenile hihi (Notiomystis cincta, a New Zealand passerine) retain a foraging behaviour from parents, or if they change in response to the behaviour of peers. We provided feeding stations to parents during chick-rearing to seed alternative access routes, and then tracked their offspring's behaviour. Once independent, juveniles formed mixed-treatment social groups, where they did not retain preferences from their time with parents. Instead, juvenile groups converged over time to use one access route­ per group, and juveniles that moved between groups switched to copy the locally favoured option. Juvenile hihi did not copy specific individuals, even if they were more familiar with the preceding bird. Our study shows that early social experiences with parents affect initial foraging decisions, but social environments encountered later on can update transmission of arbitrary behaviours. This suggests that conformity may be widespread in animal groups, with potential cultural, ecological and evolutionary consequences.
  • Boi, Simone; Mazzino, Andrea; Muratore-Ginanneschi, Paolo; Olivieri, Stefano (2018)
    One of the cornerstones of turbulent dispersion is the celebrated Taylor's formula. This formula expresses the rate of transport (i.e., the eddy diffusivity) of a tracer as a time integral of the fluid velocity autocorrelation function evaluated along the fluid particle trajectories. Here, we review the hypotheses which permit us to extend Taylor's formula to particles of any inertia. The hypotheses are independent of the details of the inertial particle model. We also show by explicit calculation that the hypotheses encompass cases when memory terms such as Basset's and Faxén's corrections are taken into account in the modeling of inertial particle dynamics.
  • COMACARE Study Groups; Humaloja, Jaana J; Lähde, Marika; Ashton, Nicholas J.; Reinikainen, Matti; Hästbacka, Johanna; Jakkula, Pekka; Friberg, Hans; Cronberg, Tobias; Pettilä, Ville; Blennow, Kaj; Zetterberg, Henrik; Skrifvars, Markus (2022)
    Aim: To determine the ability of serum glial fibrillary acidic protein (GFAp) and tau protein to predict neurological outcome after out-of-hospital cardiac arrest (OHCA). Methods: We measured plasma concentrations of GFAp and tau of patients included in the previously published COMACARE trial (NCT02698917) on intensive care unit admission and at 24, 48, and 72 h after OHCA, and compared them to neuron specific enolase (NSE). NSE concentrations were determined already during the original trial. We defined unfavourable outcome as a cerebral performance category (CPC) score of 3-5 six months after OHCA. We determined the prognostic accuracy of GFAp and tau using the receiver operating characteristic curve and area under the curve (AUROC). Results: Overall, 39/112 (35%) patients had unfavourable outcomes. Over time, both markers were evidently higher in the unfavourable outcome group (p < 0.001). At 48 h, the median (interquartile range) GFAp concentration was 1514 (886-4995) in the unfavourable versus 238 (135-463) pg/ ml in the favourable outcome group (p < 0.001). The corresponding tau concentrations were 99.6 (14.5-352) and 3.0 (2.2-4.8) pg/ml (p < 0.001). AUROCs at 48 and 72 h were 0.91 (95% confidence interval 0.85-0.97) and 0.91 (0.85-0.96) for GFAp and 0.93 (0.86-0.99) and 0.95 (0.89-1.00) for tau. Corresponding AUROCs for NSE were 0.86 (0.79-0.94) and 0.90 (0.82-0.97). The difference between the prognostic accuracies of GFAp or tau and NSE were not statistically significant. Conclusions: At 48 and 72 h, serum both GFAp and tau demonstrated excellent accuracy in predicting outcomes after OHCA but were not superior to NSE. Clinical trial registration: NCT02698917 (https://www.clinicaltrials.gov/ct2/show/NCT02698917).
  • Ahlgren, Tommy; Jalkanen, Pasi; Mizohata, Kenichiro; Tuboltsev, Vladimir; Räisänen, Jyrki; Heinola, Kalle; Tikkanen, Pertti O. (2019)
    The radiological safety of the future thermonuclear fusion devices depends critically on the total tritium inventory in the plasma-facing components. The planned method to remove tritium from the ITER reactor tungsten divertor is to perform vacuum baking. We show that tritium removal from tungsten can be enhanced by the isotope exchange mechanism by doing the baking in H-2 atmosphere. The results show that the retained deuterium from 30 keV implantation can be expected to drop almost to zero after 24h annealing at 250 degrees C in H-2 atmosphere. Annealing in vacuum requires temperatures above 400 degrees C for close to zero retention.
  • Annala, Salla; Ruggiero, Salvatore; Kangas, Hanna Liisa; Honkapuro, Samuli; Ohrling, Tiina (2022)
    The transition toward more renewable-based energy systems increases the need for new flexible resources, such as demand response (DR). Previous literature has found various barriers for DR utilization, but much of this research has focused on the initiation of DR operations or barriers in national markets and not on factors that hinder market upscaling and firm internationalization. We address this gap by analyzing interviews with 22 DR companies active in Finland, one of the early mover countries for automated DR. While most of previous research has focused on electricity DR, our interviewees also include district heating DR companies. By using the Technological Innovation System (TIS) framework, we study how the advanced regulatory and market framework and the technology rollout in Finland have affected the DR service development and the internationalization of Finnish companies. Based on our results, the DR market formation in Finland has largely relied on the Finnish transmission system operator's early decision to allow independent aggregation and the early large-scale rollout of smart meters. The advanced home market has enabled firms to develop new solutions and prove their concept. Yet, the highly structured nature of energy markets complicates the access to both advanced and less advanced foreign markets.
  • Nagarajan, Usharani; Beaune, Gregory; Lam, Andy Y. W.; Gonzalez-Rodriguez, David; Winnik, Francoise M.; Brochard-Wyart, Francoise (2021)
    While both active and granular matter have been extensively studied, here we investigate what happens when we mix the two of them, in a model system combining microparticles and cell assemblies. On a substrate covered with polystyrene or silica microparticles, we notice two regimes in the spreading of a cell aggregate: light particles are pushed by the cells and form a ring, which bonds to the substrate by adhesion forces that oppose spreading, while for heavy particles, the cell monolayer spreads above the particle bed. In both cases, cell activity is transmitted to inert beads, leading to the formation of cell-microparticle aggregates, which flicker and diffuse. We then study the formation and the spreading of hybrid aggregates of microparticles and living cells and observe phase separations and jamming transitions. Our study may have implications on processes such as cancer metastasis and development, and may guide cancer therapies based on inert particles. Interaction of active matter with geometrical and topological constraints is a topic of intense research in the recent few years due to its potential for design and control of active flow patterns. Here, the authors experimentally study the growth and expansion of cell aggregates interleaved by passive colloidal particles, showing that inert particles can reshape the collective pattern formation in cellular aggregates.
  • Kemp, Emily; Palomaki, Tommi; Ruuth, Ida A.; Boeva, Zhanna A.; Nurminen, Teemu A.; Vanska, Risto T.; Zschaechner, Laura K.; Perez, Alejandro Garcia; Hakala, Tuuli A.; Wardale, Melissa; Haeggstrom, Edward; Bobacka, Johan (2022)
    We integrated a magnetohydrodynamic fluid extractor with an amperometric glucose biosensor to develop a wearable device for non-invasive glucose monitoring. Reproducible fluid extraction through the skin and efficient transport of the extracted fluid to the biosensor surface are prerequisites for non-invasive glucose monitoring. We optimized the enzyme immobilization and the interface layer between the sensing device and the skin. The monitoring device was evaluated by extracting fluid through porcine skin followed by glucose detection at the biosensor. The biosensor featured a screen-printed layer of Prussian Blue that was coated with a layer containing glucose oxidase. Both physical entrapment of glucose oxidase in chitosan and tethering of glucose oxidase to electrospun nanofibers were evaluated. Binding of glucose oxidase to nanofibers under mild conditions provided a stable biosensor with analytical performance suitable for accurate detection of micromolar concentrations of glucose. Hydrogels of varying thickness (95-2000 mu m) as well as a thin (30 mu m) nanofibrous polycaprolactone mat were studied as an interface layer between the biosensor and the skin. The effect of mass transfer phenomena at the biosensor-skin interface on the analytical performance of the biosensor was evaluated. The sensing device detected glucose extracted through porcine skin with an apparent (overall) sensitivity of-0.8 mA/(M.cm(2)), compared to a sensitivity of-17 mA/(M.cm(2)) for measurement in solution. The amperometric response of the biosensor correlated with the glucose concentration in the fluid that had been extracted through porcine skin with the magnetohydrodynamic technique.
  • Lassmann-Klee, Paul Guenther; Lehtimäki, Lauri; Lindholm, Tuula; Malmberg, L. Pekka; Sovijärvi, Anssi; Piirilä, Päivi (2018)
    Fractional exhaled nitric oxide (F-ENO) is used to assess eosinophilic inflammation of the airways. F-ENO values are influenced by the expiratory flow rate and orally produced NO. We measured F-ENO at four different expiratory flow levels after two different mouthwashes: tap water and carbonated water. Further, we compared the alveolar NO concentration (C-ANO), maximum airway NO flux (J(awNO)) and airway NO diffusion (D-awNO) after these two mouthwashes. F-ENO was measured in 30 volunteers (healthy or asthmatic) with a chemiluminescence NO-analyser at flow rates of 30, 50, 100 and 300mL/s. A mouthwash was performed before the measurement at every flow rate. The carbonated water mouthwash significantly reduced F-ENO compared to the tap water mouthwash at all expiratory flows: 50mL/s (p
  • Rieppo, Lassi; Kokkonen, Harri T.; Kulmala, Katariina A. M.; Kovanen, Vuokko; Lammi, Mikko J.; Töyräs, Juha; Saarakkala, Simo (2017)
    Collagen forms an organized network in articular cartilage to give tensile stiffness to the tissue. Due to its long half-life, collagen is susceptible to cross-links caused by advanced glycation end-products. The current standard method for determination of cross-link concentrations in tissues is the destructive high-performance liquid chromatography (HPLC). The aim of this study was to analyze the cross-link concentrations nondestructively from standard unstained histological articular cartilage sections by using Fourier transform infrared (FTIR) microspectroscopy. Half of the bovine articular cartilage samples (n = 27) were treated with threose to increase the collagen cross-linking while the other half (n = 27) served as a control group. Partial least squares (PLS) regression with variable selection algorithms was used to predict the cross-link concentrations from the measured average FTIR spectra of the samples, and HPLC was used as the reference method for cross-link concentrations. The correlation coefficients between the PLS regression models and the biochemical reference values were r = 0.84 (p <0.001), r = 0.87 (p <0.001) and r = 0.92 (p <0.001) for hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP), and pentosidine (Pent) cross-links, respectively. The study demonstrated that FTIR microspectroscopy is a feasible method for investigating cross-link concentrations in articular cartilage. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.