Idiopathic Normal Pressure Hydrocephalus (iNPH) is a frequent neuropsychiatric entity. Clinically... more Idiopathic Normal Pressure Hydrocephalus (iNPH) is a frequent neuropsychiatric entity. Clinically it is characterised by Hakim's triad: Dementia, gait disturbance and urinary incontinence. While its symptomatology is typical, the etiology and thereby physiopathology of iNPH still remain enigmatic. This review summarizes and synthesizes different etiologic conceptions and physiopathologic aspects of iNPH. A research of literature via the PubMed/MEDLINE and the Cochrane database was conducted. Only English language articles clearly outlining a reasonable concept of physiopathology were included. Most authors advocate that iNPH is a result of chronically altered cerebrospinal fluid (CSF) dynamics, i.e. deranged CSF production, kinetics and reabsorption. In addition, there are vascular, metaboloneurodegenerative and hereditary factors. Neuroinflammation does not seem to play a significant role in the etiology of iNPH. All in all, iNPH seems to combine several pathogenetic factors leading to a self-reinforcing vicious circle. The majority of studies hint at CSF disturbances on grounds of altered hemodynamics.
The simultaneous determination of serum CA and their receptors in blood cells offers a possibilit... more The simultaneous determination of serum CA and their receptors in blood cells offers a possibility to evaluate disturbances of the DA and NA neuronal systems in man. High affinity binding sites for 3H-yohimbine in platelets, 3H-DHA on granulocytes and 3H-spiperone in lymphocytes from healthy control persons, unmedicated (n = 28), and medicated (n = 8) schizophrenics as well as from an unmedicated psychiatric control (n = 14) were investigated. Furthermore, the actual concentration of the circulating CA was determined with HPLC-ECD. In unmedicated schizophrenics as compared to controls, specific binding of 3H-spiperone to lymphocytes was markedly elevated in capacity and less in affinity as compared to controls. For beta2-receptors a significant decrease was found in capacity with no change in affinity. The changes in alpha2-receptors with a slight decrease in capacity were less distinct. The concentrations of circulating CA ranged from normal values up to a more than 3 fold increase...
Traumatic brain injury (TBI) victims are considered to be at high risk for infection. The purpose... more Traumatic brain injury (TBI) victims are considered to be at high risk for infection. The purpose of this cohort study was to delineate the rates, types and risk factors for infection in TBI patients. Retrospective surveillance of infections was conducted for all TBI patients, aged ‡18 years, cared for at the
Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. ... more Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. The purpose of this study was to delineate the frequency, types and risk factors for infection in patients with TBI who undergo neurosurgery. Retrospective surveillance of infections in patients with TBI, aged ≥18 years who underwent neurosurgery in University of Crete between 1999 and 2005. Two hundred fifty-eight patients (76.7% men) who underwent 342 procedures were included. One hundred forty-two infections occurred, mainly lower respiratory tract infections (44.4% of the number of infections) and surgical site infections (SSIs) (25.4%). In multivariate analysis, SSIs were independently associated with the length of stay (p < 0.001), history of malignancy (p = 0.008), CSF leak (p = 0.012), any concomitant infection (p = 0.010), particularly urinary tract infections (p = 0.001) and the use of lumbar and/or ventricular drains (p = 0.005). Meningitis was independently associated with the total length of stay (p < 0.001), the need for intubation and mechanical ventilation beyond surgery (p = 0.028) and the presence of a lumbar and/or ventricular drain (p < 0.001). Respiratory tract infections were common in patients with TBI who underwent surgery with Acinetobacter spp. being the emerging offending pathogens. Device-related postoperative communication of the CSF and the environment was a significant risk factor for SSI development and meningitis in particular. Malignancy was an independent risk factor for SSIs. The prevalence of the offending pathogens must be determined institution by institution for the establishment of proper antibiotic treatment on suspicion.
The association between genetic variations in the cytochrome P450 (CYP) family genes and patholog... more The association between genetic variations in the cytochrome P450 (CYP) family genes and pathological conditions related to long-term exposure to organochlorine compounds (OCs) deserves further elucidation. OCs are persistent organic pollutants with bioaccumulative and lipophilic characteristics. They can act as endocrine disruptors and perturb cellular mechanisms. Prolonged exposure to OCs has been associated with different pathological manifestations. CYP genes are responsible for transcribing enzymes essential in xenobiotic metabolism. Therefore, polymorphisms in these genetic sequences a. alter the metabolic pathways, b. induce false cellular responses, and c. may provoke pathological conditions. The main aim of this review is to define the interaction between parameters a, b and c at a mechanistic/molecular level, with references in clinical cases.
Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. ... more Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. The purpose of this study was to delineate the frequency, types and risk factors for infection in patients with TBI who undergo neurosurgery. Retrospective surveillance of infections in patients with TBI, aged ≥18 years who underwent neurosurgery in University of Crete between 1999 and 2005. Two hundred fifty-eight patients (76.7% men) who underwent 342 procedures were included. One hundred forty-two infections occurred, mainly lower respiratory tract infections (44.4% of the number of infections) and surgical site infections (SSIs) (25.4%). In multivariate analysis, SSIs were independently associated with the length of stay (p < 0.001), history of malignancy (p = 0.008), CSF leak (p = 0.012), any concomitant infection (p = 0.010), particularly urinary tract infections (p = 0.001) and the use of lumbar and/or ventricular drains (p = 0.005). Meningitis was independently associated with the total length of stay (p < 0.001), the need for intubation and mechanical ventilation beyond surgery (p = 0.028) and the presence of a lumbar and/or ventricular drain (p < 0.001). Respiratory tract infections were common in patients with TBI who underwent surgery with Acinetobacter spp. being the emerging offending pathogens. Device-related postoperative communication of the CSF and the environment was a significant risk factor for SSI development and meningitis in particular. Malignancy was an independent risk factor for SSIs. The prevalence of the offending pathogens must be determined institution by institution for the establishment of proper antibiotic treatment on suspicion.
Abstract A three-degree-of-freedom dynamic contact model with friction and lubricant contact is i... more Abstract A three-degree-of-freedom dynamic contact model with friction and lubricant contact is introduced for thermal fly-height control of a near-contact flying slider. The proposed model addresses the issue of contact with a molecularly thin lubricant layer and includes a third degree-of-freedom, roll. Neither lubricant contact nor roll has been accounted for in previous models of the head–disk interface. Roll angle rotations allow for possible contact at other slider features such as the contact pads, which may induce destabilizing moments to ...
The noradrenaline, dopamine and serotonin metabolites methoxyhydroxyphenylglycol (MHPG), homovani... more The noradrenaline, dopamine and serotonin metabolites methoxyhydroxyphenylglycol (MHPG), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA), as well as the cyclic nucleotides c-AMP and c-GMP were estimated in urine samples of five normal volunteers. Ten control samples and two samples after cannabis use were analyzed for each volunteer. Cannabis use caused significant decreases in MHPG and c-AMP, and increases in HVA, while 5-HIAA and c-GMP excretion remained unchanged. The results indicate that cannabis use interferes with catecholaminergic mechanisms in man, decreasing the noradrenaline and increasing dopamine turnover, probably through action on presynaptic receptors.
Carbon nanofibers (CNF) are versatile nanomaterials that are widely used in various fields of sci... more Carbon nanofibers (CNF) are versatile nanomaterials that are widely used in various fields of science and technology. As a consequence, animals as well as humans may be exposed to such compounds via different routes. We hypothesized that oral intake of CNF will lead to an inflammatory reaction and consequently induce behavioral impairments. To address this issue, rats were fed with 500mg/kgCNF for 14days and their locomotor activity, emotional status and cognition were quantified by testing the animals in an open field set-up, elevated plus maze and in the universal problem solving box which provides information about motivation and cognition. The behavioral tests were performed 3 times within 10days. At the end of the experiment, blood samples were collected and the plasma concentrations of IL-6, IL-8, IL-1β, IL-10 and IL-18 were measured. Our results demonstrated an inflammatory reaction determined by a significantly elevated IL-6 concentration. This, however, was counteracted by an even more pronounced increase in IL-10. The behavioral effects were restricted mainly to a decrease in locomotor activity which was significant in the open field test, as well as the elevated plus maze. Other parameters indicative of cognitive performance were not influenced and also the emotional status was largely unaffected. In conclusion, our results revealed that oral intake of 500mg/kgCNF induced some adverse effects, which, however, can be still partially compensated by the organism.
In this work, a numerical model is developed in order to investigate the adaptability of the mult... more In this work, a numerical model is developed in order to investigate the adaptability of the multi-pump multi-piston power take-off (MP2PTO) system of a novel wave energy converter (WEC). This model is realized in the MATLAB/SIMULINK environment, using the multi-body dynamics solver Multibody™, which is based on the open-source tool WEC-Sim. Furthermore, the hydrodynamic coefficients are calculated using the open-source code NEMOH. After providing the description of the model, it is validated against experimental results and an analytical model, showing good agreement with both. Subsequently, simulations for a single floater device with a multi-piston pump (MPP) unit using our numerical model are carried out to demonstrate the adaptability of the WEC. In addition, the results demonstrate that the MPP with a simple control strategy can extract more energy than any non-adaptable piston pump under various sea states. Finally, a floater blanket (an array of interconnected floaters) model is developed to shed some light on the hydrodynamic response and the performance of MPPs. The developed numerical model will be used in the future to optimize the MP2PTO configuration, and to develop an energy maximization control strategy for the MP2PTO system.
This paper summarizes the submissions to a recently announced contact-mechanics modeling challeng... more This paper summarizes the submissions to a recently announced contact-mechanics modeling challenge. The task was to solve a typical, albeit mathematically fully defined problem on the adhesion between nominally flat surfaces. The surface topography of the rough, rigid substrate, the elastic properties of the indenter, as well as the short-range adhesion between indenter and substrate, were specified so that diverse quantities of interest, e.g., the distribution of interfacial stresses at a given load or the mean gap as a function of load, could be computed and compared to a reference solution. Many different solution strategies were pursued, ranging from traditional asperity-based models via Persson theory and brute-force computational approaches, to real-laboratory experiments and all-atom molecular dynamics simulations of a model, in which the original assignment was scaled down to the atomistic scale. While each submission contained satisfying answers for at least a subset of the posed questions, efficiency, versatility, and accuracy differed between methods, the more precise methods being, in general, computationally more complex. The aim of this paper is to provide both theorists and experimentalists with benchmarks to decide which method is the most appropriate for a particular application and to gauge the errors associated with each one.
The association between genetic variations in the cytochrome P450 (CYP) family genes and patholog... more The association between genetic variations in the cytochrome P450 (CYP) family genes and pathological conditions related to long-term exposure to organochlorine compounds (OCs) deserves further elucidation. OCs are persistent organic pollutants with bioaccumulative and lipophilic characteristics. They can act as endocrine disruptors and perturb cellular mechanisms. Prolonged exposure to OCs has been associated with different pathological manifestations. CYP genes are responsible for transcribing enzymes essential in xenobiotic metabolism. Therefore, polymorphisms in these genetic sequences a. alter the metabolic pathways, b. induce false cellular responses, and c. may provoke pathological conditions. The main aim of this review is to define the interaction between parameters a, b and c at a mechanistic/molecular level, with references in clinical cases.
The involvement of growth factors (GFs) in the pathogenesis of lumbar intervertebral disc (ID) he... more The involvement of growth factors (GFs) in the pathogenesis of lumbar intervertebral disc (ID) herniation and the spontaneous resorption of herniated ID fragments remains only partially elucidated. A simultaneous assessment of the transcript levels of numerous GFs and their association with clinical and epidemiological profiles of human ID herniation would provide valuable insight into the biology and clinical course of the disease. In the present study, we examined simultaneously the transcript levels of vascular endothelial growth factor (VEGF), transforming growth factor β1 (TGF‑β1), basic fibroblast growth factor 2 (bFGF2), platelet derived growth factor (PDGF) isoforms and receptors, epidermal growth factor (EGF) and insulin growth factor‑1 (IGF‑1) in herniated and control ID specimens and investigated their correlation with the clinicopathological profiles of patients suffering from symptomatic lumbar ID herniation. GF mRNA expression levels were determined by RT-qPCR in 63 surgical specimens from lumbar herniated discs and 10 control ID specimens. Multiple positive correlations were observed between the transcript levels of the GFs examined in the ID herniation group. VEGF mRNA expression was significantly increased in the protruding compared with the extruded discs. Intense and acute pain significantly upregulated the PDGF transcript levels. Significant negative correlations were observed between the patient body mass index and the transcript levels of VEGF and PDGF receptors. Our findings support the hypothesis of the involvement of GFs in the natural history of ID herniation. GFs synergistically act in herniated IDs. Increased VEGF expression possibly induces the neovascularization process in the earliest stages of ID herniation. PDGF‑C and ‑D play a role in the acute phase of radiculopathy in a metabolic response for tissue healing. A molecular effect, in addition to the biomechanical effect of obesity in the pathogenesis of ID herniation is also implied.
A multi-pump, multi-piston power take-off wave energy converter (MP2PTO WEC) has been proposed fo... more A multi-pump, multi-piston power take-off wave energy converter (MP2PTO WEC) has been proposed for use with a novel renewable energy harvester termed the Ocean Grazer. The MP2PTO WEC utilizes wave motion to pump–via buoys connected to pistons–working fluid within a closed circuit and store it as potential energy that can be converted to electricity via turbines. This paper introduces the mechanical design and model-based performance prediction of a single-piston pump that constitutes the basic building block for the MP2PTO WEC. Results provide preliminary validation of aqueous lubrication as a viable means of reducing friction and wear, suggesting that water-based hydraulic fluids can prohibit solid contact at the piston-cylinder interface while reducing volumetric leakage, and allowing for an estimation of the energy extraction efficiency for the mechanical pumping system. Pending more thorough and extended tribological investigations using the methodology introduced in this paper, findings suggest that the overall system efficiency will be dictated by the hydrodynamics of the buoys actuating the pumping system.
Volume 2: Dynamics, Vibration and Control; Energy; Fluids Engineering; Micro and Nano Manufacturing, 2014
Copyright {\textcopyright} 2014 by ASME. A novel wave energy converter, termed the Ocean Grazer, ... more Copyright {\textcopyright} 2014 by ASME. A novel wave energy converter, termed the Ocean Grazer, designed to extract energy from waves of varying profiles and energy contents has recently been proposed by the University of Groningen. The authors have performed preliminary modeling work to predict the behavior of the converter's power take-off system, and constructed a proof-of-concept prototype to validate basic model predictions.
OBJECT The authors performed a prospective study to define the prevalence and microbiological cha... more OBJECT The authors performed a prospective study to define the prevalence and microbiological characteristics of infections in patients undergoing craniotomy and to clarify the risk factors for post-craniotomy meningitis. METHODS Patients older than 18 years who underwent nonstereotactic craniotomies between January 2006 and December 2008 were included. Demographic, clinical, laboratory, and microbiological data were systemically recorded. Patient characteristics, craniotomy type, and pre- and postoperative variables were evaluated as risk factors for meningitis RESULTS Three hundred thirty-four procedures were analyzed (65.6% involving male patients). Traumatic brain injury was the most common reason for craniotomy. Almost 40% of the patients developed at least 1 infection. Ventilatorassociated pneumonia (VAP) was the most common infection recorded (22.5%) and Acinetobacter spp. were isolated in 44% of the cases. Meningitis was encountered in 16 procedures (4.8%), and CSF cultures ...
Idiopathic Normal Pressure Hydrocephalus (iNPH) is a frequent neuropsychiatric entity. Clinically... more Idiopathic Normal Pressure Hydrocephalus (iNPH) is a frequent neuropsychiatric entity. Clinically it is characterised by Hakim's triad: Dementia, gait disturbance and urinary incontinence. While its symptomatology is typical, the etiology and thereby physiopathology of iNPH still remain enigmatic. This review summarizes and synthesizes different etiologic conceptions and physiopathologic aspects of iNPH. A research of literature via the PubMed/MEDLINE and the Cochrane database was conducted. Only English language articles clearly outlining a reasonable concept of physiopathology were included. Most authors advocate that iNPH is a result of chronically altered cerebrospinal fluid (CSF) dynamics, i.e. deranged CSF production, kinetics and reabsorption. In addition, there are vascular, metaboloneurodegenerative and hereditary factors. Neuroinflammation does not seem to play a significant role in the etiology of iNPH. All in all, iNPH seems to combine several pathogenetic factors leading to a self-reinforcing vicious circle. The majority of studies hint at CSF disturbances on grounds of altered hemodynamics.
The simultaneous determination of serum CA and their receptors in blood cells offers a possibilit... more The simultaneous determination of serum CA and their receptors in blood cells offers a possibility to evaluate disturbances of the DA and NA neuronal systems in man. High affinity binding sites for 3H-yohimbine in platelets, 3H-DHA on granulocytes and 3H-spiperone in lymphocytes from healthy control persons, unmedicated (n = 28), and medicated (n = 8) schizophrenics as well as from an unmedicated psychiatric control (n = 14) were investigated. Furthermore, the actual concentration of the circulating CA was determined with HPLC-ECD. In unmedicated schizophrenics as compared to controls, specific binding of 3H-spiperone to lymphocytes was markedly elevated in capacity and less in affinity as compared to controls. For beta2-receptors a significant decrease was found in capacity with no change in affinity. The changes in alpha2-receptors with a slight decrease in capacity were less distinct. The concentrations of circulating CA ranged from normal values up to a more than 3 fold increase...
Traumatic brain injury (TBI) victims are considered to be at high risk for infection. The purpose... more Traumatic brain injury (TBI) victims are considered to be at high risk for infection. The purpose of this cohort study was to delineate the rates, types and risk factors for infection in TBI patients. Retrospective surveillance of infections was conducted for all TBI patients, aged ‡18 years, cared for at the
Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. ... more Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. The purpose of this study was to delineate the frequency, types and risk factors for infection in patients with TBI who undergo neurosurgery. Retrospective surveillance of infections in patients with TBI, aged ≥18 years who underwent neurosurgery in University of Crete between 1999 and 2005. Two hundred fifty-eight patients (76.7% men) who underwent 342 procedures were included. One hundred forty-two infections occurred, mainly lower respiratory tract infections (44.4% of the number of infections) and surgical site infections (SSIs) (25.4%). In multivariate analysis, SSIs were independently associated with the length of stay (p < 0.001), history of malignancy (p = 0.008), CSF leak (p = 0.012), any concomitant infection (p = 0.010), particularly urinary tract infections (p = 0.001) and the use of lumbar and/or ventricular drains (p = 0.005). Meningitis was independently associated with the total length of stay (p < 0.001), the need for intubation and mechanical ventilation beyond surgery (p = 0.028) and the presence of a lumbar and/or ventricular drain (p < 0.001). Respiratory tract infections were common in patients with TBI who underwent surgery with Acinetobacter spp. being the emerging offending pathogens. Device-related postoperative communication of the CSF and the environment was a significant risk factor for SSI development and meningitis in particular. Malignancy was an independent risk factor for SSIs. The prevalence of the offending pathogens must be determined institution by institution for the establishment of proper antibiotic treatment on suspicion.
The association between genetic variations in the cytochrome P450 (CYP) family genes and patholog... more The association between genetic variations in the cytochrome P450 (CYP) family genes and pathological conditions related to long-term exposure to organochlorine compounds (OCs) deserves further elucidation. OCs are persistent organic pollutants with bioaccumulative and lipophilic characteristics. They can act as endocrine disruptors and perturb cellular mechanisms. Prolonged exposure to OCs has been associated with different pathological manifestations. CYP genes are responsible for transcribing enzymes essential in xenobiotic metabolism. Therefore, polymorphisms in these genetic sequences a. alter the metabolic pathways, b. induce false cellular responses, and c. may provoke pathological conditions. The main aim of this review is to define the interaction between parameters a, b and c at a mechanistic/molecular level, with references in clinical cases.
Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. ... more Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. The purpose of this study was to delineate the frequency, types and risk factors for infection in patients with TBI who undergo neurosurgery. Retrospective surveillance of infections in patients with TBI, aged ≥18 years who underwent neurosurgery in University of Crete between 1999 and 2005. Two hundred fifty-eight patients (76.7% men) who underwent 342 procedures were included. One hundred forty-two infections occurred, mainly lower respiratory tract infections (44.4% of the number of infections) and surgical site infections (SSIs) (25.4%). In multivariate analysis, SSIs were independently associated with the length of stay (p < 0.001), history of malignancy (p = 0.008), CSF leak (p = 0.012), any concomitant infection (p = 0.010), particularly urinary tract infections (p = 0.001) and the use of lumbar and/or ventricular drains (p = 0.005). Meningitis was independently associated with the total length of stay (p < 0.001), the need for intubation and mechanical ventilation beyond surgery (p = 0.028) and the presence of a lumbar and/or ventricular drain (p < 0.001). Respiratory tract infections were common in patients with TBI who underwent surgery with Acinetobacter spp. being the emerging offending pathogens. Device-related postoperative communication of the CSF and the environment was a significant risk factor for SSI development and meningitis in particular. Malignancy was an independent risk factor for SSIs. The prevalence of the offending pathogens must be determined institution by institution for the establishment of proper antibiotic treatment on suspicion.
Abstract A three-degree-of-freedom dynamic contact model with friction and lubricant contact is i... more Abstract A three-degree-of-freedom dynamic contact model with friction and lubricant contact is introduced for thermal fly-height control of a near-contact flying slider. The proposed model addresses the issue of contact with a molecularly thin lubricant layer and includes a third degree-of-freedom, roll. Neither lubricant contact nor roll has been accounted for in previous models of the head–disk interface. Roll angle rotations allow for possible contact at other slider features such as the contact pads, which may induce destabilizing moments to ...
The noradrenaline, dopamine and serotonin metabolites methoxyhydroxyphenylglycol (MHPG), homovani... more The noradrenaline, dopamine and serotonin metabolites methoxyhydroxyphenylglycol (MHPG), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA), as well as the cyclic nucleotides c-AMP and c-GMP were estimated in urine samples of five normal volunteers. Ten control samples and two samples after cannabis use were analyzed for each volunteer. Cannabis use caused significant decreases in MHPG and c-AMP, and increases in HVA, while 5-HIAA and c-GMP excretion remained unchanged. The results indicate that cannabis use interferes with catecholaminergic mechanisms in man, decreasing the noradrenaline and increasing dopamine turnover, probably through action on presynaptic receptors.
Carbon nanofibers (CNF) are versatile nanomaterials that are widely used in various fields of sci... more Carbon nanofibers (CNF) are versatile nanomaterials that are widely used in various fields of science and technology. As a consequence, animals as well as humans may be exposed to such compounds via different routes. We hypothesized that oral intake of CNF will lead to an inflammatory reaction and consequently induce behavioral impairments. To address this issue, rats were fed with 500mg/kgCNF for 14days and their locomotor activity, emotional status and cognition were quantified by testing the animals in an open field set-up, elevated plus maze and in the universal problem solving box which provides information about motivation and cognition. The behavioral tests were performed 3 times within 10days. At the end of the experiment, blood samples were collected and the plasma concentrations of IL-6, IL-8, IL-1β, IL-10 and IL-18 were measured. Our results demonstrated an inflammatory reaction determined by a significantly elevated IL-6 concentration. This, however, was counteracted by an even more pronounced increase in IL-10. The behavioral effects were restricted mainly to a decrease in locomotor activity which was significant in the open field test, as well as the elevated plus maze. Other parameters indicative of cognitive performance were not influenced and also the emotional status was largely unaffected. In conclusion, our results revealed that oral intake of 500mg/kgCNF induced some adverse effects, which, however, can be still partially compensated by the organism.
In this work, a numerical model is developed in order to investigate the adaptability of the mult... more In this work, a numerical model is developed in order to investigate the adaptability of the multi-pump multi-piston power take-off (MP2PTO) system of a novel wave energy converter (WEC). This model is realized in the MATLAB/SIMULINK environment, using the multi-body dynamics solver Multibody™, which is based on the open-source tool WEC-Sim. Furthermore, the hydrodynamic coefficients are calculated using the open-source code NEMOH. After providing the description of the model, it is validated against experimental results and an analytical model, showing good agreement with both. Subsequently, simulations for a single floater device with a multi-piston pump (MPP) unit using our numerical model are carried out to demonstrate the adaptability of the WEC. In addition, the results demonstrate that the MPP with a simple control strategy can extract more energy than any non-adaptable piston pump under various sea states. Finally, a floater blanket (an array of interconnected floaters) model is developed to shed some light on the hydrodynamic response and the performance of MPPs. The developed numerical model will be used in the future to optimize the MP2PTO configuration, and to develop an energy maximization control strategy for the MP2PTO system.
This paper summarizes the submissions to a recently announced contact-mechanics modeling challeng... more This paper summarizes the submissions to a recently announced contact-mechanics modeling challenge. The task was to solve a typical, albeit mathematically fully defined problem on the adhesion between nominally flat surfaces. The surface topography of the rough, rigid substrate, the elastic properties of the indenter, as well as the short-range adhesion between indenter and substrate, were specified so that diverse quantities of interest, e.g., the distribution of interfacial stresses at a given load or the mean gap as a function of load, could be computed and compared to a reference solution. Many different solution strategies were pursued, ranging from traditional asperity-based models via Persson theory and brute-force computational approaches, to real-laboratory experiments and all-atom molecular dynamics simulations of a model, in which the original assignment was scaled down to the atomistic scale. While each submission contained satisfying answers for at least a subset of the posed questions, efficiency, versatility, and accuracy differed between methods, the more precise methods being, in general, computationally more complex. The aim of this paper is to provide both theorists and experimentalists with benchmarks to decide which method is the most appropriate for a particular application and to gauge the errors associated with each one.
The association between genetic variations in the cytochrome P450 (CYP) family genes and patholog... more The association between genetic variations in the cytochrome P450 (CYP) family genes and pathological conditions related to long-term exposure to organochlorine compounds (OCs) deserves further elucidation. OCs are persistent organic pollutants with bioaccumulative and lipophilic characteristics. They can act as endocrine disruptors and perturb cellular mechanisms. Prolonged exposure to OCs has been associated with different pathological manifestations. CYP genes are responsible for transcribing enzymes essential in xenobiotic metabolism. Therefore, polymorphisms in these genetic sequences a. alter the metabolic pathways, b. induce false cellular responses, and c. may provoke pathological conditions. The main aim of this review is to define the interaction between parameters a, b and c at a mechanistic/molecular level, with references in clinical cases.
The involvement of growth factors (GFs) in the pathogenesis of lumbar intervertebral disc (ID) he... more The involvement of growth factors (GFs) in the pathogenesis of lumbar intervertebral disc (ID) herniation and the spontaneous resorption of herniated ID fragments remains only partially elucidated. A simultaneous assessment of the transcript levels of numerous GFs and their association with clinical and epidemiological profiles of human ID herniation would provide valuable insight into the biology and clinical course of the disease. In the present study, we examined simultaneously the transcript levels of vascular endothelial growth factor (VEGF), transforming growth factor β1 (TGF‑β1), basic fibroblast growth factor 2 (bFGF2), platelet derived growth factor (PDGF) isoforms and receptors, epidermal growth factor (EGF) and insulin growth factor‑1 (IGF‑1) in herniated and control ID specimens and investigated their correlation with the clinicopathological profiles of patients suffering from symptomatic lumbar ID herniation. GF mRNA expression levels were determined by RT-qPCR in 63 surgical specimens from lumbar herniated discs and 10 control ID specimens. Multiple positive correlations were observed between the transcript levels of the GFs examined in the ID herniation group. VEGF mRNA expression was significantly increased in the protruding compared with the extruded discs. Intense and acute pain significantly upregulated the PDGF transcript levels. Significant negative correlations were observed between the patient body mass index and the transcript levels of VEGF and PDGF receptors. Our findings support the hypothesis of the involvement of GFs in the natural history of ID herniation. GFs synergistically act in herniated IDs. Increased VEGF expression possibly induces the neovascularization process in the earliest stages of ID herniation. PDGF‑C and ‑D play a role in the acute phase of radiculopathy in a metabolic response for tissue healing. A molecular effect, in addition to the biomechanical effect of obesity in the pathogenesis of ID herniation is also implied.
A multi-pump, multi-piston power take-off wave energy converter (MP2PTO WEC) has been proposed fo... more A multi-pump, multi-piston power take-off wave energy converter (MP2PTO WEC) has been proposed for use with a novel renewable energy harvester termed the Ocean Grazer. The MP2PTO WEC utilizes wave motion to pump–via buoys connected to pistons–working fluid within a closed circuit and store it as potential energy that can be converted to electricity via turbines. This paper introduces the mechanical design and model-based performance prediction of a single-piston pump that constitutes the basic building block for the MP2PTO WEC. Results provide preliminary validation of aqueous lubrication as a viable means of reducing friction and wear, suggesting that water-based hydraulic fluids can prohibit solid contact at the piston-cylinder interface while reducing volumetric leakage, and allowing for an estimation of the energy extraction efficiency for the mechanical pumping system. Pending more thorough and extended tribological investigations using the methodology introduced in this paper, findings suggest that the overall system efficiency will be dictated by the hydrodynamics of the buoys actuating the pumping system.
Volume 2: Dynamics, Vibration and Control; Energy; Fluids Engineering; Micro and Nano Manufacturing, 2014
Copyright {\textcopyright} 2014 by ASME. A novel wave energy converter, termed the Ocean Grazer, ... more Copyright {\textcopyright} 2014 by ASME. A novel wave energy converter, termed the Ocean Grazer, designed to extract energy from waves of varying profiles and energy contents has recently been proposed by the University of Groningen. The authors have performed preliminary modeling work to predict the behavior of the converter's power take-off system, and constructed a proof-of-concept prototype to validate basic model predictions.
OBJECT The authors performed a prospective study to define the prevalence and microbiological cha... more OBJECT The authors performed a prospective study to define the prevalence and microbiological characteristics of infections in patients undergoing craniotomy and to clarify the risk factors for post-craniotomy meningitis. METHODS Patients older than 18 years who underwent nonstereotactic craniotomies between January 2006 and December 2008 were included. Demographic, clinical, laboratory, and microbiological data were systemically recorded. Patient characteristics, craniotomy type, and pre- and postoperative variables were evaluated as risk factors for meningitis RESULTS Three hundred thirty-four procedures were analyzed (65.6% involving male patients). Traumatic brain injury was the most common reason for craniotomy. Almost 40% of the patients developed at least 1 infection. Ventilatorassociated pneumonia (VAP) was the most common infection recorded (22.5%) and Acinetobacter spp. were isolated in 44% of the cases. Meningitis was encountered in 16 procedures (4.8%), and CSF cultures ...
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Papers by Antonis Vakis