Micro-Computed Tomography (µCT) as a Tool for High-Resolution 3D Imaging and Analysis of Intraocular Lenses: Feasibility and Proof of the Methodology to Evaluate YAG Pits.

INTRODUCTION: Posterior capsule opacification (PCO) is the most frequent late sequelae after successful cataract surgery. Neodymium:yttrium aluminum garnet (Nd:YAG) laser capsulotomy is considered the gold standard and a well-accepted, safe, and effective measure in treating PCO. However, iatrogenic damage of the intraocular lens (IOL) due to inappropriate focusing is a quite common side effect. These permanent defects (YAG pits) can critically affect overall optical quality. METHODS: In this laboratory study, we used the micro-computed tomography (µCT) technique to obtain high-resolution 3D images of the lens and the YAG pits. RESULTS: To the best of our knowledge, this is the first description of a detailed analysis of IOLs with µCT technology. This non-destructive technique seems to be ideal for comparative studies, measuring dimensions of the damage, and visualizing shooting channels within the material. CONCLUSION: µCT is excellently suited to examine an IOL in detail, analyze optics and haptics in three dimensions, and to describe all kinds of changes within the IOL without damaging it.

Pore space extraction and characterization of sack paper using µ-CT.

We show that attenuation X-ray microcomputed tomography (µ-CT) offers a route to extract the three-dimensional pore space of paper reliably enough to distinguish samples of the same kind of paper. Here, we consider two sack kraft papers for cement bags with different basis weights and thicknesses. Sample areas of approximately 5 mm2 with a resolution of 1.5 µm are considered, i.e. sizes that exceed sample areas of 2 mm2 for which the pore structure was previously studied in the literature. The image segmentation is based on indicator kriging as a local method that removes ambiguities in assigning voxels as pore or as fibre. The microstructures of the two samples are statistically compared in terms of descriptors such as sheet thickness, porosity, fractions of externally accessible pores and mean geodesic tortuosity. We demonstrate that a quantitative comparison of samples in terms of porosity and thickness requires a common definition of the sheet surfaces. Finally, the statistical pore space analysis based on the µ-CT scans reliably reveals structural differences between the two paper samples, but only when several descriptors are used. LAY DESCRIPTION: This paper is a seemingly abundant material. Its intrinsic porosity enables a vast number of commercial applications. Particularly packing products, e.g. cement bags, often incorporate sack kraft paper due to its high porosity and its additional mechanical strength. A direct quantification of the porosity of sack kraft papers is, hence, particularly desirable. However, experimental quantification of paper porosity or its pore network properties is difficult and often highly indirect. A nondestructive statistical analysis of the 3D microstructure holds the promise to directly assess the pores. In particular, X-ray microcomputed tomography (µ-CT), frequently with sub-µm resolution, has been established as a method to study the fibre and pore structure of paper. The question arises, whether statistical analysis of the microstructure based on µ-CT imaging is sufficient to reliably distinguish between different sack kraft papers. Here, we explore whether the pore structure of paper can be extracted and statistically analysed for larger sample areas despite the fact that a larger sample size directly translates into a lower resolution of the µ-CT scan. We expect that a large sample size increases the region of interest on the basis of which samples can be better distinguished. A lowered resolution poses a severe challenge for the reliable identification of voxel data as pores or as fibres, because the contrast between paper fibres (made of cellulose) and air, which is established due to X-ray absorption, is weak. We show that we can reliably assign each voxel by using an indicator kriging as a two-step method. This method performs an initial voxel identification based on the overall distribution of measured grey values and refines the identification by inspecting the local environment of each voxel. For the pore space extracted in such a way, we can then compute quantities that are related to the geometry and connectivity properties of the pores. Furthermore, we address a paper-born challenge for such an analysis, i.e. we cannot always unambiguously tell whether a pore is located inside the paper sheet or at the surface of the paper. The way the paper surfaces are extracted from the microstructure decisively determines the final specifications of the predicted properties. A significant distinction of the samples is only possible when comparing the properties of the pore network.

What are depressive symptoms in acutely ill patients with schizophrenia spectrum disorder?

BACKGROUND: Aim was to examine depressive symptoms in acutely ill schizophrenia patients on a single symptom basis and to evaluate their relationship with positive, negative and general psychopathological symptoms. METHODS: Two hundred and seventy-eight patients suffering from a schizophrenia spectrum disorder were analysed within a naturalistic study by the German Research Network on Schizophrenia. Using the Calgary Depression Scale for Schizophrenia (CDSS) depressive symptoms were examined and the Positive and Negative Syndrome Scale (PANSS) was applied to assess positive, negative and general symptoms. Correlation and factor analyses were calculated to detect the underlying structure and relationship of the patient's symptoms. RESULTS: The most prevalent depressive symptoms identified were depressed mood (80%), observed depression (62%) and hopelessness (54%). Thirty-nine percent of the patients suffered from depressive symptoms when applying the recommended cut-off of a CDSS total score of >6 points at admission. Negligible correlations were found between depressive and positive symptoms as well as most PANSS negative and global symptoms despite items on depression, guilt and social withdrawal. The factor analysis revealed that the factor loading with the PANSS negative items accounted for most of the data variance followed by a factor with positive symptoms and three depression-associated factors. LIMITATIONS: The naturalistic study design does not allow a sufficient control of study results for the effect of different pharmacological treatments possibly influencing the appearance of depressive symptoms. CONCLUSION: Results suggest that depressive symptoms measured with the CDSS are a discrete symptom domain with only partial overlap with positive or negative symptoms.

Should early improvement be re-defined to better predict the maintenance of response in first-episode schizophrenia patients?

OBJECTIVE: To evaluate the predictive validity of early response in first-episode schizophrenia within a 1-year follow-up trial and to compare the resulting cutoff to the currently proposed early response definition (20% improvement by week 2). METHOD: Receiver operator characteristic (ROC) analyses were used to identify the predictive validity of the psychopathological improvement of treatment from week 1 to week 8, regarding the maintenance of response until week 52 as well as to define the most reasonable cutoff in 132 first-episode patients. The Youden Index (maximum of sensitivity and specificity) was used to compare the newly developed and the commonly used early response definition. RESULTS: Starting with week 6, a reasonable validity to predict the maintenance of response was found (area under the curve = 0.721) with the best fitting cutoff being a 51.6% PANSS total score improvement. Using this cutoff 74 patients (56%) were correctly identified to become responder and maintain response during follow-up (sensitivity: 0.747). The Youden Index was higher applying the newly developed early response cutoff featuring higher specificity compared to the commonly used early response definition. CONCLUSION: Regarding long-term treatment, it seems more appropriate to base predictions of the patient's maintenance of response not before 6 weeks of treatment.

The relationship of Akathisia with treatment emergent suicidality among patients with first-episode schizophrenia treated with haloperidol or risperidone.

Akathisia as well as younger age, early illness onset and discharge are important risk factors for suicidality in patients with first-episode schizophrenia. The aim of the present study was to analyze on a single case basis the relationship between a sudden increase in suicidality, anxiety symptoms, medication dosing and clinician- and patient-rated akathisia. A small subsample of patients demonstrated a positive relationship between suicidality and akathisia scores within the titration period of the study medication.

Insight in schizophrenia-course and predictors during the acute treatment phase of patients suffering from a schizophrenia spectrum disorder.

BACKGROUND: To analyse insight of illness during the course of inpatient treatment, and to identify influencing factors and predictors of insight. METHODS: Insight into illness was examined in 399 patients using the item G12 of the Positive and Negative Syndrome Scale ("lack of insight and judgement"). Ratings of the PANSS, HAMD, UKU, GAF, SOFAS, SWN-K and Kemp's compliance scale were performed and examined regarding their potential association with insight. The item G12 was kept as an ordinal variable to compare insight between subgroups of patients. RESULTS: Almost 70% of patients had deficits in their insight into illness at admission. A significant improvement of impairments of insight during the treatment (p<0.0001) was observed. At admission more severe positive and negative symptoms, worse functioning and worse adherence were significantly associated with poorer insight. Less depressive symptoms (p=0.0004), less suicidality (p=0.0218), suffering from multiple illness-episodes (p<0.0001) and worse adherence (p=0.0012) at admission were identified to be significant predictors of poor insight at discharge. CONCLUSION: The revealed predictors might function as treatment targets in order to improve insight and with it outcome of schizophrenia.

Adsorption and desorption of CO on Ni decorated stepped Rh(553).

Vicinal surfaces are important in surface science, as they show interesting electronic structures and reactivities due to the steps. In this paper the adsorption and desorption of carbon monoxide on the stepped Rh(553) surface decorated with Ni is reported. With 0.1 to 0.3 monolayer Ni on Rh(553) one and two atoms broad Ni wires along the Rh steps are formed. The adsorption and desorption of carbon monoxide on these surfaces is investigated using thermal desorption spectroscopy (TDS) and reflection absorption infra red spectroscopy (RAIRS). TDS shows a marked change from just one broad TDS peak on pure Rh(553) to 4 distinct peaks with increasing Ni decoration. RAIRS shows that already at 0.1 monolayer Ni the CO adsorption states on bridge sites on the Rh step atoms are completely quenched. In addition it is shown that with Ni films up to 3 monolayer the on top adsorption sites for CO on Ni are preferred over the bridge and hollow adsorption sites in contrast to what is known from the Ni(111) surface.

Methanol adsorption on Cu(110) and the angular distribution of the reaction products.

Integral and angle resolved thermal desorption spectroscopies were used to study methanol adsorption and oxidation on clean and oxygen covered Cu(110) surfaces. Special emphasis was put on the Cu-CuO stripe phase, which forms when the Cu(110) surface is covered with 0.25 ML of oxygen. In the temperature regime between 200 and 300 K associative desorption of methanol and water takes place, showing a normal desorption character with peaks shifting to lower temperature with increasing coverage and with a nearly cosine angular desorption distribution. In the temperature range of about 350 K formaldehyde, hydrogen, and again methanol desorb nearly concomitantly in the form of a very narrow peak (full width at half maximum=10 K), with peaks shifting to higher temperature with increasing methanol coverage. The angular distribution of these peaks is strongly forward focused, indicating activation barriers being involved. In the case of the Cu-CuO stripe phase the angular distribution of the desorption products is clearly different in the [110] and [001] azimuthal directions, demonstrating the influence of the border lines between the copper and the copper oxide stripes on the desorption process.

CO adsorption and CO and O coadsorption on Rh(111) studied by reflection absorption infrared spectroscopy and density functional theory.

The adsorption of carbon monoxide on Rh(111) and on oxygen modified Rh(111) was investigated using thermal desorption spectroscopy, reflection absorption infrared spectroscopy (RAIRS), and density functional theory. The results show that CO adsorbs on Rh(111) in on top sites at low coverages. With increasing coverage hollow sites and bridge sites get occupied according to the RAIRS results. A new vibrational feature at high wave numbers was found in the on top region of the CO stretching frequency. This feature can be explained by a local high density CO structure where two CO molecules are adsorbed in the ( radical3x radical3)R30 degrees structure. The coadsorption of oxygen and carbon monoxide leads to a shift of the CO stretching frequency to higher wave numbers with increasing O to CO ratio. CO adsorption on a (2x1) oxygen layer is possible and RAIRS shows that the CO adsorbs in on top and most likely in bridge sites in this case.

A reflection absorption infrared spectroscopy and density-functional theory investigation of methanol dehydrogenation on Rh(111)V alloy surfaces.

The dehydrogenation reaction of methanol on a Rh(111) surface, a Rh(111)V subsurface alloy, and on a Rh(111)V islands surface has been studied by thermal-desorption spectroscopy, reflection absorption infrared spectroscopy, and density-functional theory calculations. The full monolayer of methanol forms a structure with a special geometry with methanol rows, where two neighboring molecules have different oxygen-rhodium distances. They are close enough to form a H-bonded bilayer structure, with such a configuration, where every second methanol C-O bond is perpendicular to the surface on both Rh(111) and on the Rh(111)V subsurface alloy. The Rh(111)V subsurface alloy is slightly more reactive than the Rh(111) surface which is due to the changes in the electronic structure of the surface leading to slightly different methanol species on the surface. The Rh(111)V islands surface is the most reactive surface which is due to a new reaction mechanism that involves a methanol species stabilized up to about 245 K, partial opening of the methanol C-O bond, and dissociation of the product carbon monoxide. The latter two reactions also lead to a deactivation of the Rh(111)V islands surface.

Adsorption and reaction of methanol on clean and oxygen modified rhodium/vanadium surface alloys.

The dehydrogenation of methanol on Rh(111), on a Rh(111)/V subsurface alloy and on Rh(111) with V islands has been studied with and without preadsorbed oxygen using a supersonic molecular beam and temperature programmed desorption. The reactivity is highest for the V islands surface without oxygen. But this surface is deactivated due to CO dissociation. The subsurface alloy is less reactive than the islands, but still more active than the Rh(111) surface. The reaction products are carbon monoxide and hydrogen only. With preadsorbed oxygen Rh(111) is the most active surface, but a strong dependence of the activity on the amount of preadsorbed oxygen is found for all three surfaces. The reaction products with preadsorbed oxygen are water, hydrogen, carbon dioxide and carbon monoxide. The reactions follow the same mechanism on all surfaces, but the activation energy of the individual reaction steps is different leading to significant changes in the thermal desorption spectra and in King and Wells-type experiments.

The surface properties of tetradecyltrimethylammonium bromide observed by capillary electrophoresis.

The electroosmotic flow (EOF) is measured as a function of tetradecyltrimethylammonium bromide (TTAB) concentration and is shown to have distinct zones that are pH dependent. The data is correlated with previously proposed surface structures ranging from unimolecular adsorption to hemimicelles and micelles of TTAB adsorbed on the hydrated fused silica. A plot of the TTAB concentration at zero EOF versus pH shows that the zero point of charge (zpc) is pH dependent and that a linear extrapolation of the data intercepts close to the pH value for the zpc of a fused-silica surface. This shows that different surface properties at different pH values at any given TTAB concentration are generally dealt with. Therefore, these pH-dependent structures of the fused-silica surface have to be taken into account while studying these phenomena.

Electrocoagulation (EC)--science and applications.

Although electrocoagulation is an evolving technology that is being effectively applied today for wastewater treatment, the paucity of scientific understanding of the complex chemical and physical processes involved is limiting future design and hindering progress. The objective of this review through a survey of the literature is to bring the chemistry and physical processes involved into perspective and to focus attention on those areas critically needing research.

Plasma chemistry as a tool for green chemistry, environmental analysis and waste management.

The applications of plasma chemistry to environmental problems and to green chemistry are emerging fields that offer unique opportunities for advancement. There has been substantial progress in the application of plasmas to analytical diagnostics and to waste reduction and waste management. This review discusses the chemistry and physics necessary to a basic understanding of plasmas, something that has been missing from recent technical reviews. The current status of plasmas in environmental chemistry is summarized and emerging areas of application for plasmas are delineated. Plasmas are defined and discussed in terms of their properties that make them useful for environmental chemistry. Information is drawn from diverse fields to illustrate the potential applications of plasmas in analysis, materials modifications and hazardous waste treatments.