Hydrodynamic properties of the Certas hydrocephalus shunt

2013 ◽  
Vol 11 (2) ◽  
pp. 198-204 ◽  
Author(s):  
Zofia Czosnyka ◽  
John D. Pickard ◽  
Marek Czosnyka
Keyword(s):  
High Pressures ◽  
Performance Level ◽  
Laboratory Evaluation ◽  
Hydrodynamic Resistance ◽  
Hydrodynamic Parameters ◽  
Adjustable Valve ◽  
Drainage Rate ◽  
Csf Drainage ◽  
Opening And Closing

Object Independent testing of hydrocephalus shunts provides information about the quality of CSF drainage after shunt implantation. Moreover, hydrodynamic parameters of a valve assessed in the laboratory create a comparative pattern for testing of shunt performance in vivo. This study sought to assess the hydrodynamic parameters of the Certas valve, a new model of a hydrocephalus shunt. Methods The Certas valve is an adjustable ball-on-spring hydrocephalus valve. It can be adjusted magnetically in vivo in 7 steps, equally distributed within the therapeutic limit for hydrocephalus, and the eighth step at high pressures intended to block CSF drainage. The magnetically adjustable rotor is designed to prevent accidental readjustment of the valve in a magnetic field, including clinical MRI. Results The pressure-flow performance curves, as well as the operating, opening, and closing pressures, were stable, fell within the specified limits, and changed according to the adjusted performance levels. The valve at settings 1–7 demonstrated low hydrodynamic resistance of 1.4 mm Hg/ml/min, increasing to 5.1 mm Hg/ml/min after connection of a distal drain provided by the manufacturer. At performance Level 8 the hydrodynamic resistance was greater than 20 mm Hg/ml/min. External programming of the valve proved to be easy and reliable. The valve is safe in 3-T MRI and the performance level of the valve is unlikely to be changed. However, with the valve implanted, distortion of the image is substantial. Integration of the valve with the SiphonGuard limits the drainage rate. Conclusions In the laboratory the Certas valve appears to be a reliable differential-pressure adjustable valve. Laboratory evaluation should be supplemented by results of a clinical audit in the future.

scholarly journals Structure and Identification of Solenin: A Novel Fibrous Protein from BivalveSolen grandisLigament

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Jun Meng ◽  
Gang-Sheng Zhang ◽  
Zeng-Qiong Huang
Keyword(s):  
Mechanical Performance ◽  
Type I ◽  
Fibrous Proteins ◽  
Repeat Sequences ◽  
Fibrous Protein ◽  
Secondary Structure Analysis ◽  
Solen Grandis ◽  
Opening And Closing ◽  
Insight Into

Fibrous proteins, which derived from natural sources, have been acting as templates for the production of new materials for decades, and most of them have been modified to improve mechanical performance. Insight into the structures of fibrous proteins is a key step for fabricating of bioinspired materials. Here, we revealed the microstructure of a novel fibrous protein: solenin fromSolen grandisligament and identified the protein by MALDI-TOF-TOF-MS and LC-MS-MS analyses. We found that the protein fiber has no hierarchical structure and is homologous to keratin type II cytoskeletal 1 and type I cytoskeletal 9-like, containing “SGGG,” “SYGSGGG,” “GS,” and “GSS” repeat sequences. Secondary structure analysis by FTIR shows that solenin is composed of 41.8%β-sheet, 16.2%β-turn, 26.5%α-helix, and 9.8% disordered structure. We believe that theβ-sheet structure and those repeat sequences which form “glycine loops” may give solenin excellence elastic and flexible properties to withstand tensile stress caused by repeating opening and closing of the shell valves in vivo. This paper contributes a novel fibrous protein for the protein materials world.

Erroneous Measurement of Intracranial Pressure Caused by Simultaneous Ventricular Drainage: A Hydrodynamic Model Study

Neurosurgery ◽  
1989 ◽  
Vol 24 (3) ◽  
pp. 348-354 ◽  
Author(s):  
Harold A. Wilkinson ◽  
Jorge Yarzebski ◽  
Edward C. Wilkinson ◽  
Frederick A. Anderson
Keyword(s):  
Intracranial Pressure ◽  
High Pressures ◽  
Ventricular Catheter ◽  
Csf Flow ◽  
Pressure Setting ◽  
Clinical Observations ◽  
Csf Drainage ◽  
Model Study ◽  
Csf Production ◽  
Brain Pressure

Abstract Intracranial pressure (ICP) is often measured from intraventricular catheters, a technique that allows therapeutic drainage of ventricular cerebrospinal fluid (CSF) as an aid in controlling ICP and circumventing obstruction. Drainage of CSF simultaneously with ongoing ICP measurement has been advocated as safe and efficient, and devices are commercially available to permit this practice; however, this concept has been seriously challenged, based on clinical observations. The inaccuracy induced by simultaneous CSF drainage and ICP monitoring is quantitated in this report in a mechanical brain model using a standard ventricular catheter. The following conclusions have been confirmed: 1) rapid CSF drainage induces a severe artifactual reduction in measured ICP, more extreme at higher pressures; 2) calibrated slower rates of CSF drainage produce a severe, although less immediate, reduction in measured ICP; 3) severe artifact appears even in the presence of continuous CSF outflow, so a system that measures ICP only in the presence of CSF flow does not prevent artifact; 4) with simultaneous CSF drainage, measured ICP is determined more by the outflow pressure setting than by actual brain pressure; 5) Since ICP elevation of 25 to 30 mm Hg blocks CSF production, even slow fluid drainage at high pressures should ultimately lead to ventricular collapse and severe artifact.

Alveolar septal folding and lung inflation history

1991 ◽  
Vol 71 (6) ◽  
pp. 2369-2379 ◽  
Author(s):  
E. H. Oldmixon ◽  
F. G. Hoppin
Keyword(s):  
De Novo ◽  
Light And Electron Microscopy ◽  
Alveolar Epithelium ◽  
Microscopic Appearance ◽  
Lung Inflation ◽  
History Of ◽  
Opening And Closing ◽  
Alveolar Septa ◽  
Lung Preparation

On the basis of microscopic appearance of excised lungs, it has been thought that alveolar septa may fold and unfold during deflation and inflation. We suspected that this appearance might depend heavily on the inflation history of the lung preparation. We therefore studied, by light and electron microscopy, dog, rabbit, and rat lungs fixed over a range of inflation pressures and after a variety of inflation histories. Septal folding, as suggested by the configurations of the air spaces, by the placement of the fine and coarse connective tissue elements, and by the pattern of infolding of alveolar epithelium, was readily seen with some inflation protocols but was absent with others. Pressure at fixation was not as important as events before fixation; deflation to 3 cmH2O did not induce folding, and inflation to 16 cmH2O did not undo the folds. This range corresponds with concepts of critical opening and closing pressures. We suggest that folds form de novo during experimental preparation; one need not postulate that septal folding was present in vivo.

A Prototype Infant Incubator for Heliox Therapy

2006 ◽  
Vol 40 (2) ◽  
pp. 150-163 ◽  
Author(s):  
Clifford J. Singhaus ◽  
Suzanne M. Touch ◽  
Jay S. Greenspan ◽  
Marla R. Wolfson ◽  
Thomas H. Shaffer
Keyword(s):  
Neonatal Intensive Care ◽  
Animal Studies ◽  
Performance Criteria ◽  
In Vitro Tests ◽  
Original Design ◽  
Experimental Conditions ◽  
Infant Incubator ◽  
Opening And Closing

Abstract Heliox (Hx) gas has been shown to improve pulmonary function in infants, but methods for its delivery are invasive and problematic. To this end, we modified an Isolette (Hill-Rom Air-Shields) infant incubator (Hxl) to deliver Hx respiratory gas mixtures noninvasively while providing thermal stability for neonatal care in the Neonatal Intensive Care Unit (NICU). In vitro tests and in vivo animal studies were performed to compare the original design specifications and established baseline performance criteria for the Hxl design. The experimental environments at 50% and 80% relative humidity (RH) consisted of helium (He) with 21% and 50% O2 and control (C) of 21% and 50% O2 with the balance nitrogen (N2). Elapsed times to steady state (SS) and recovery time back to SS (OCDss) due to opening and closing the door were recorded for each variable. All rabbits survived and appeared comfortable during all experimental conditions. These data show that the newly designed Isolette provides similar thermal, O2, CO2, and RH responses as the control incubator. Based on these positive safety/efficacy studies, study of the therapeutic impact of Hxl care on neonatal growth and development is in progress.

Laboratory Evaluation of Low-Cost Wearable Sensors for Measuring Head Impacts in Sports

2018 ◽  
Vol 34 (4) ◽  
pp. 320-326 ◽  
Author(s):  
Abigail M. Tyson ◽  
Stefan M. Duma ◽  
Steven Rowson
Keyword(s):  
Short Duration ◽  
Statistical Tests ◽  
Low Cost ◽  
Wearable Sensors ◽  
Sampling Rate ◽  
Sensor Technology ◽  
Laboratory Evaluation ◽  
Head Impacts ◽  
Hybrid Iii

Advances in low-cost wearable head impact sensor technology provide potential benefits regarding sports safety for both consumers and researchers. However, previous laboratory evaluations are not directly comparable and do not incorporate test conditions representative of unhelmeted impacts. This study addresses those limitations. The xPatch by X2 Biosystems and the SIM-G by Triax Technologies were placed on a National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform with a Hybrid III neck which underwent impact tests using a pendulum. Impact conditions included helmeted, padded impactor to bare head, and rigid impactor to bare head to represent long- and short-duration impacts seen in helmeted and unhelmeted sports. The wearable sensors were evaluated on their kinematic accuracy by comparing results to reference sensors located at the headform center of gravity. Statistical tests for equivalence were performed on the slope of the linear regression between wearable sensors and reference. The xPatch gave equivalent measurements to the reference in select longer-duration impacts, whereas the SIM-G had large variance leading to no equivalence. For the short-duration impacts, both wearable sensors underpredicted the reference. This error can be improved with increases in sampling rate from 1 to 1.5 kHz. Follow-up evaluations should be performed on the field to identify error in vivo.

Effect of Hyperbaric Oxygen Treatment on Nitric Oxide and Oxygen Free Radicals in Rat Brain

2000 ◽  
Vol 83 (4) ◽  
pp. 2022-2029 ◽  
Author(s):  
Ikram M. Elayan ◽  
Milton J. Axley ◽  
Paruchuri V. Prasad ◽  
Stephen T. Ahlers ◽  
Charles R. Auker
Keyword(s):  
Nitric Oxide ◽  
Free Radicals ◽  
Rat Brain ◽  
Hyperbaric Oxygen ◽  
High Pressures ◽  
Oxygen Free Radicals ◽  
In Vivo Microdialysis ◽  
Sprague Dawley ◽  
Fourfold Increase

Oxygen (O2) at high pressures acts as a neurotoxic agent leading to convulsions. The mechanism of this neurotoxicity is not known; however, oxygen free radicals and nitric oxide (NO) have been suggested as contributors. This study was designed to follow the formation of oxygen free radicals and NO in the rat brain under hyperbaric oxygen (HBO) conditions using in vivo microdialysis. Male Sprague-Dawley rats were exposed to 100% O2 at a pressure of 3 atm absolute for 2 h. The formation of 2,3-dihydroxybenzoic acid (2,3-DHBA) as a result of perfusing sodium salicylate was followed as an indicator for the formation of hydroxyl radicals. 2,3-DHBA levels in hippocampal and striatal dialysates of animals exposed to HBO conditions were not significantly different from controls. However, rats treated under the same conditions showed a six- and fourfold increase in nitrite/nitrate, break down products of NO decomposition, in hippocampal and striatal dialysates, respectively. This increase was completely blocked by the nitric oxide synthase (NOS) inhibitor l-nitroarginine methyl ester (l-NAME). Using neuronal NOS, we determined the NOS O2 K m to be 158 ± 28 (SD) mmHg, a value which suggests that production of NO by NOS would increase approximately four- to fivefold under hyperbaric O2 conditions, closely matching the measured increase in vivo. The increase in NO levels may be partially responsible for some of the detrimental effects of HBO conditions.

Too many compromises: survey research and the spectre of communism

2016 ◽  
Vol 8 (1) ◽  
pp. 197-214 ◽  
Author(s):  
Stefan Schwarzkopf
Keyword(s):  
Survey Research ◽  
High Pressures ◽  
Social Research ◽  
Marketing Research ◽  
Scientific Practices ◽  
Archival Research ◽  
Social Scientists ◽  
Content Type ◽  
The Way

Purpose – This paper aims to chart the influence of McCarthyism and of FBI surveillance practices on a number of prominent American social scientists, market researchers, opinion pollsters and survey research practitioners during the post-war years. Hitherto disparate sets of historical evidence on how Red Scare tactics influenced social researchers and marketing scientists are brought together and updated with evidence from original archival research. Design/methodology/approach – The paper draws on the existing secondary literature on how social research practitioners and social scientists reacted to the unusually high pressures on academic freedom during the McCarthy era. It supplements this review with evidence obtained from archival research, including declassified FBI files. The focus of this paper is set on prominent individuals, mainly Bernard Berelson, Samuel Stouffer, Hadley Cantril, Robert S. Lynd, Paul F. Lazarsfeld, Herta Herzog, Ernest Dichter, but also the Frankfurt School in exile. Findings – Although some of the historiography presents American social scientists and practitioners in the marketing research sector as victims of McCarthyism and FBI surveillance, it can also be shown that virtually all individuals in focus here also developed strategies of accommodation, compromise and even opportunism to benefit from the climate of suspicion brought about by the prevailing anti-Communism. Social implications – Anyone interested in questions about the morality of marketing, market research and opinion polling as part of the social sciences practiced in vivo will need to pay attention to the way these social-scientific practices became tarnished by the way prominent researchers accommodated and at times even abetted McCarthyism. Originality/value – Against the view of social scientists as harassed academic minority, evidence is presented in this paper which shows American social scientists who researched market-related phenomena, like media, voters choices and consumer behaviour, in a different light. Most importantly, this paper for the first time presents archival evidence on the scale of Paul F. Lazarsfeld’s surveillance by the FBI.

Deciphering the brittle failure of eclogites at high-pressures: hydrofractures as fluid-escape pathways

2020 ◽  
Author(s):  
Michał Bukała ◽  
Károly Hidas ◽  
Carlos J. Garrido ◽  
Christopher Barnes ◽  
Iwona Klonowska ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Outer Zone ◽  
Passive Margin ◽  
National Agency ◽  
Vein Formation ◽  
Iapetus Ocean ◽  
Eclogite Facies ◽  
Textural Relationship ◽  
Opening And Closing

<p>The Tsäkkok lens (northern Scandinavian Caledonides) represents the outermost part of the rifted Baltica passive margin and consists of sediments and pillow basalts of MORB affinity that were metamorphosed in eclogite facies. The Tsäkkok eclogites underwent metamorphism in a cold subduction regime (~8 °C/km) at the onset of the Iapetus Ocean closure. These rocks record pervasive high-pressure, fracturing during prograde dehydration at eclogite-facies conditions reaching up to 2.2 GPa and 590 ºC. Locally, the omphacite-dominated groundmass is transected by fractures sealed either by omphacitite or garnetite veins. Garnetite veins form a dense network that disrupt intact eclogite blocks, whereas omphacitite is found in rare, single veins. The garnetite veins are dominated by dense, poikiloblastic garnet clusters and display two chemically different zones, i.e., a high-Mn inner zone and a low-Mn outer zone. Detailed microstructural and geochemical mapping by EDS-EBSD SEM revealed that the high-Mn inner zone is disrupted and sealed by the low-Mn garnet zone. Garnets in the vein usually show little elongation and moderate intracrystalline substructure that is dominated by slightly changing misorientations without clear subgrain boundaries. By contrast, garnets of the sealed domain display an abrupt grain size reduction and anomalously high density of sharp intracrystalline misorientations in equant grains. The interstitial space between garnet grains in both of the inner and outer zones of the vein is infilled by omphacite + rutile + quartz + phengite + glaucophane.</p><p>The textural relationship between the inner- and outer zones of the garnetite vein implies syn-deformation growth of the outer zone, while the mineral assemblage attests for high-pressure conditions of the vein formation. Considering the lack of significant offset along the vein, we interpret the observed microstructures as formed during the sudden opening and closing of a brittle fracture, typical of hydrofracturing, and fast crystal growth assisted by high-pressure fluids. Presumably, these fractures constitute a fluid escape pathway during dehydration at prograde/peak conditions.</p><p>Research funded by NCN project no. 2019/33/N/ST10/01479 (M.Bukała) and no. 2014/14/E/ST10/00321 (J.Majka), as well as the The Polish National Agency for the Academic Exchange scholarship no. PPN/IWA/2018/1/00046/U/0001 given to M.Bukała.</p><p> </p>

Adjustable shunt valve–induced magnetic resonance imaging artifact: a comparative study

2010 ◽  
Vol 113 (1) ◽  
pp. 74-78 ◽  
Author(s):  
Ahmed K. Toma ◽  
Andrew Tarnaris ◽  
Joan P. Grieve ◽  
Laurence D. Watkins ◽  
Neil D. Kitchen
Keyword(s):  
Mr Imaging ◽  
Pulse Sequence ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Fast Spin Echo ◽  
Mr Images ◽  
Shunt Valve ◽  
Adjustable Valve ◽  
Imaging Artifact

Object In this paper, the authors' goal was to compare the artifact induced by implanted (in vivo) adjustable shunt valves in spin echo, diffusion weighted (DW), and gradient echo MR imaging pulse sequences. Methods The MR images obtained in 8 patients with proGAV and 6 patients with Strata II adjustable shunt valves were assessed for artifact areas in different planes as well as the total volume for different pulse sequences. Results Artifacts induced by the Strata II valve were significantly larger than those induced by proGAV valve in spin echo MR imaging pulse sequence (29,761 vs 2450 mm3 on T2-weighted fast spin echo, p = 0.003) and DW images (100,138 vs 38,955 mm3, p = 0.025). Artifacts were more marked on DW MR images than on spin echo pulse sequencse for both valve types. Conclusions Adjustable valve–induced artifacts can conceal brain pathology on MR images. This should influence the choice of valve implantation site and the type of valve used. The effect of artifacts on DW images should be highlighted pending the development of less MR imaging artifact–inducing adjustable shunt valves.

Diagnosis and correction of immune system disorders

1986 ◽  
Vol 67 (4) ◽  
pp. 289-294 ◽  
Author(s):  
L. V. Kovalchuk ◽  
A. N. Cheredeev
Keyword(s):  
Immune System ◽  
Clinical Immunology ◽  
The State ◽  
Laboratory Evaluation ◽  
In Vitro Methods ◽  
Wide Range ◽  
High Degree

Modern clinical immunology has a wide range of tests that can detect immune system disorders with a sufficiently high degree of accuracy. Laboratory evaluation of the immune system is performed using in vivo and in vitro methods. In vivo methods allow to judge the state of the immune system at the organism level.

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