193 nm ArF laser ablation and patterning of chitosan thin films

This paper reports laser ablation studies on spin coated bio polymer chitosan films, β-l,4-1inked 2-amino-2-deoxy-D-glucopyranose. Chitosan has been irradiated using an ArF laser emitting at 193 nm. An ablation threshold of FT = 858 mJcm-2 has been determined from etch rate measurements. Laser ablated chitosan is characterised using white light interferometry, scanning electron microscopy and thermo-gravimetric analysis. Laser ablation of chitosan is discussed in terms of thermal and photoacoustic mechanisms. Heat transfer is simulated to assist in the understanding of laser irradiated chitosan using a finite element method and the software package COMSOL Multi-Physics™. As a demonstrator, a micro-array of square structures in the form of a crossed grating has been fabricated by laser ablation using a mask projection scanning method. Initial investigations shown no evidence of thermal damage occurring to the adjacent chitosan when operating at a moderately low laser fluence of 110 mJcm-2

Investigation into the efficacy of CO2 lasers for modifying the factors influencing biocompatibility of a polymeric biomaterial in comparison with an F2 excimer laser

Enhancement of the biocompatibility of a material by means of laser radiation has been amply demonstrated previously. Due to efficient absorption of the energy, short wavelengths and energies per pulse, polymers are usually processed using UV lasers, but the processing of polymers with IR lasers has also been demonstrated previously. In this work a comparative study for the surface modification of nylon 6,6 has been conducted in order to vary the parameters driving biocompatibility (surface topography, hydrophobic reactions, hydrophilic reactions and surface chemistry) using CO2 and excimer lasers. Topographical changes were analysed using white light interferometry which indicated that both laser systems could be implemented for modifying the topography of nylon 6,6. Variations in the surface chemistry were evaluated using EDX and XPS analysis and showed that the O2 increased and decreased for the CO2 and F2 laser irradiated samples, respectively. Modification of the hydrophobic and hydrophilic reactions was quantified by measuring the contact angle, which was found to increase in all instances for both laser systems. It is proposed that the increase in contact angle, especially for the CO2 laser irradiated samples, is due to a change in wetting regime as a result of the surface pattern produced

193 nm ArF laser ablation and patterning of chitosan thin films

This paper reports laser ablation studies on spin coated bio polymer chitosan films, β-l,4-1inked 2-amino-2-deoxy-D-glucopyranose. Chitosan has been irradiated using an ArF laser emitting at 193 nm. An ablation threshold of FT = 858 mJcm-2 has been determined from etch rate measurements. Laser ablated chitosan is characterised using white light interferometry, scanning electron microscopy and thermo-gravimetric analysis. Laser ablation of chitosan is discussed in terms of thermal and photoacoustic mechanisms. Heat transfer is simulated to assist in the understanding of laser irradiated chitosan using a finite element method and the software package COMSOL Multi-Physics™. As a demonstrator, a micro-array of square structures in the form of a crossed grating has been fabricated by laser ablation using a mask projection scanning method. Initial investigations shown no evidence of thermal damage occurring to the adjacent chitosan when operating at a moderately low laser fluence of 110 mJcm-2

On the effects of using CO2 and F2 lasers to modify the wettability of a polymeric biomaterial.

Enhancement of the surface properties of a material by means of laser radiation has been amply demonstrated previously. In this work a comparative study for the surface modification of nylon 6,6 has been conducted in order to vary the wettability characteristics using CO2 and excimer lasers. This was done by producing 50 μm spaced (with depths between 1 and 10 μm) trench-like patterns using various laser parameters such as varying the laser power for the CO2 laser and number of pulses for the excimer laser. Topographical changes were analysed using optical microscopy and white light interferometry which indicated that both laser systems can be implemented for modifying the topography of nylon 6,6. Variations in the surface chemistry were evaluated using energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy analysis and showed that the O2 increased by up to 1.5% At. and decreased by up to 1.6% At. for the CO2 and F2 laser patterned samples, respectively. Modification of the wettability characteristics was quantified by measuring the advancing contact angle, which was found to increase in all instances for both laser systems. Emery paper roughened samples were also analysed in the same manner to determine that the topographical pattern played a major role in the wettability characteristics of nylon 6,6. From this, it is proposed that the increase in contact angle for the laser processed samples is due to a mixed intermediate state wetting regime owed to the periodic surface roughness brought about by the laser induced trench-like topographical patterns

Reproducibility in the absence of selective reporting : An illustration from large-scale brain asymmetry research

Altres ajuts: Max Planck Society (Germany).The problem of poor reproducibility of scientific findings has received much attention over recent years, in a variety of fields including psychology and neuroscience. The problem has been partly attributed to publication bias and unwanted practices such as p-hacking. Low statistical power in individual studies is also understood to be an important factor. In a recent multisite collaborative study, we mapped brain anatomical left-right asymmetries for regional measures of surface area and cortical thickness, in 99 MRI datasets from around the world, for a total of over 17,000 participants. In the present study, we revisited these hemispheric effects from the perspective of reproducibility. Within each dataset, we considered that an effect had been reproduced when it matched the meta-analytic effect from the 98 other datasets, in terms of effect direction and significance threshold. In this sense, the results within each dataset were viewed as coming from separate studies in an "ideal publishing environment," that is, free from selective reporting and p hacking. We found an average reproducibility rate of 63.2% (SD = 22.9%, min = 22.2%, max = 97.0%). As expected, reproducibility was higher for larger effects and in larger datasets. Reproducibility was not obviously related to the age of participants, scanner field strength, FreeSurfer software version, cortical regional measurement reliability, or regional size. These findings constitute an empirical illustration of reproducibility in the absence of publication bias or p hacking, when assessing realistic biological effects in heterogeneous neuroscience data, and given typically-used sample sizes

ENIGMA and global neuroscience: A decade of large-scale studies of the brain in health and disease across more than 40 countries

This review summarizes the last decade of work by the ENIGMA (Enhancing NeuroImaging Genetics through Meta Analysis) Consortium, a global alliance of over 1400 scientists across 43 countries, studying the human brain in health and disease. Building on large-scale genetic studies that discovered the first robustly replicated genetic loci associated with brain metrics, ENIGMA has diversified into over 50 working groups (WGs), pooling worldwide data and expertise to answer fundamental questions in neuroscience, psychiatry, neurology, and genetics. Most ENIGMA WGs focus on specific psychiatric and neurological conditions, other WGs study normal variation due to sex and gender differences, or development and aging; still other WGs develop methodological pipelines and tools to facilitate harmonized analyses of "big data" (i.e., genetic and epigenetic data, multimodal MRI, and electroencephalography data). These international efforts have yielded the largest neuroimaging studies to date in schizophrenia, bipolar disorder, major depressive disorder, post-traumatic stress disorder, substance use disorders, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism spectrum disorders, epilepsy, and 22q11.2 deletion syndrome. More recent ENIGMA WGs have formed to study anxiety disorders, suicidal thoughts and behavior, sleep and insomnia, eating disorders, irritability, brain injury, antisocial personality and conduct disorder, and dissociative identity disorder. Here, we summarize the first decade of ENIGMA's activities and ongoing projects, and describe the successes and challenges encountered along the way. We highlight the advantages of collaborative large-scale coordinated data analyses for testing reproducibility and robustness of findings, offering the opportunity to identify brain systems involved in clinical syndromes across diverse samples and associated genetic, environmental, demographic, cognitive, and psychosocial factors

Novel genetic loci associated with hippocampal volume

The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness