Biodegradation of porous versus non-porous poly(L-lactic acid) films

The influence of porosity on the degradation rate of poly(L-lactic acid) (PLLA) films was investigated in vitro and in vivo. Non-porous, porous and combi (porous with a non-porous layer) PLLA films were used. Changes in Mw, Mn, polydispersity (Mw/Mn) ratio, melting temperature (T _m), heat of fusion, tensile strength, E-modulus, mass and the remaining surface area of cross-sections of the PLLA films were measured. In general, during the degradation process, the porous film has the highest Mw, Mn, Mw/Mn ratio and T _m, while the non-porous film has the lowest. In contrast, the highest heat of fusion values were observed for the non-porous film, indicating the presence of relatively smaller molecules forming crystalline domains more easily. The tensile strength and E-modulus of the non-porous film decrease faster than those of the porous and the combi film. None of the three types of films showed massive mass loss in vitro nor a significant decrease in remaining polymer surface area in light microscopical sections in vitro and in vivo. Heavy surface erosion of the non-porous layer of the combi film was observed after 180 days, turning the combi film into a porous film. This is also indicated by the changes in tensile strength, Mw, Mw/Mn, T _m and heat of fusion as a function of time. It is concluded that non-porous PLLA degrades faster than porous PLLA. Thus, in our model, porosity is an important determinant of the degradation rate of PLLA films.     

Recovery of acetylcholine release and choline acetyltransferase activity after freezing-induced degeneration of rat soleus muscle

In order to study the effect of synaptic contact on the amounts of choline acetyltransferase (ChAT) and acetylcholine (ACh) in the nerve terminals and on their ability to release ACh, a freeze-thaw procedure was developed as a means to induce long lasting degeneration of rat soleus muscle. It was found that 4 days after the freeze thaw procedure the preparation did not contract upon direct electric stimulation and the level of creatine kinase (CK) was below detection. The preparation contained about 15% of the ChAT activity and 15% of the ACh content of the controls. The ACh release evoked by 50 mM KCl was 25% of controls, but it was, when expressed as a fraction of the ACh content, about twice as high as that in control muscles. At day 12, the preparation still did not contract and the level of CK was less than 5% of controls. The ChAT activity and the ACh content were 40% and 20% of controls, respectively. However, no release of ACh could be evoked by 50 mM KCl. At days 28 and 58 the preparation contracted upon stimulation of the nerve; the CK activity had recovered to about 20% and the ACh content to 40%, while the ChAT activity did not increase above 40%. The KCl-evoked ACh release had recovered to 20-30% of controls. The results indicate that freezing destroyed muscle cells and most intramuscular nerve branches. Subsequent regeneration of muscle fibres was slow, probably because freezing had killed many satellite cells in the muscle. Because the ChAT activity at day 12 had recovered when CK was almost absent and the preparation failed to contract, we conclude that there was expression of ChAT activity in 'nerve terminals' which do not make contact with regenerated muscle cells, although little if any ACh was released from these sites.     

Cognitive psychology meets psychometric theory: On the relation between process models for decision making and latent variable models for individual differences.

This article analyzes latent variable models from a cognitive psychology perspective. We start by discussing work by Tuerlinckx and De Boeck (2005), who proved that a diffusion model for 2-choice response processes entails a 2-parameter logistic item response theory (IRT) model for individual differences in the response data. Following this line of reasoning, we discuss the appropriateness of IRT for measuring abilities and bipolar traits, such as pro versus contra attitudes. Surprisingly, if a diffusion model underlies the response processes, IRT models are appropriate for bipolar traits but not for ability tests. A reconsideration of the concept of ability that is appropriate for such situations leads to a new item response model for accuracy and speed based on the idea that ability has a natural zero point. The model implies fundamentally new ways to think about guessing, response speed, and person fit in IRT. We discuss the relation between this model and existing models as well as implications for psychology and psychometrics. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Risk Planning and Management for the Panama Canal Expansion Program

In April 2006, the Panama Canal Authority formally proposed a major expansion of the canal to increase its capacity and make it more productive, safe, and efficient. This proposal included cost and schedule estimates for completing the expansion and was supported overwhelmingly by the citizens of Panama in an October 2006 public referendum. Given the conceptual level of design at the time of the proposal and the inherent uncertainty in a project of this magnitude at the early stages of engineering, a comprehensive risk analysis was performed to develop a contingency model for the total expansion program cost and schedule. This contingency model is based on a Monte Carlo simulation of the cost and schedule estimates, taking into account the most significant risks identified for the project. The resulting model provides contingency assessments for duration and total cost and sensitivity analysis of the risks; it also allows for multiple scenario planning and ultimately supports overall risk management. This paper presents a project case study that focuses on the contingency model development and the resulting risk management and contingency resolution processes.     

New Concepts of Quality Assurance in Analytical Chemistry: Will They Influence the Way We Conduct Science in General?

According to the guide Vocabulary in Metrology (VIM3) (JCGM, 2008 JCGM, J.C.F.G.I.M. 2008. JCGM 200: 2008 International vocabulary of metrology — Basic and general concepts and associated terms (VIM) Vocabulaire international de métrologie — Concepts fondamentaux et généraux et termes associés (VIM), International Organization for Standardization Geneva ISBN, 3(Vim), p.104. Available at: http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2008.pdf. [Google Scholar]), the definition of the concepts of trueness and accuracy has been revised, which has an important impact on analytical chemistry. Additionally, Eurachem/CITAC has published a new edition of the guide to Quantifying Uncertainty in Analytical Measurement (QUAM) (CITAC and Eurachem, 2012 CITAC, and Eurachem. (2012). Quantifying uncertainty in analytical measurement. BIPM 3rd ed., pp.1–133. Available at: http://www.measurementuncertainty.org/mu/QUAM2000-1.pdf. [Google Scholar]). These two documents, together, form a new basis for the evaluation of data. Results of prominent technologies of inductively coupled plasma mass spectrometry (ICP-MS), for determination of chloride-isotope ratios (³⁵Cl/³⁷Cl) and inductively coupled plasma optical emission spectrometry (ICP-OES) for determination of sodium, were evaluated in terms of the true level of uncertainty and revealed a genuine problem for science that was not addressed in VIM3 and QUAM. Comparison of theory and experimentation definitely requires statistical tools, but in contemporary science two approaches to the implementation of statistics in decision making are used: 1. Short-term precision and 2. long-term precision. Both approaches are valid and both are described using the same methods of statistics. However, they lead to completely different conclusions and decisions. Despite good intentions and new concepts, as well as practices and procedures for quality assurance, it is shown by these two examples that these efforts may be inadequate or mislead scientists into making major mistakes in the decision-making process. A set of equations is supplied, which are based on the propagation of uncertainty, and the implication of results and conclusions for other fields of science is discussed.     

l-Carnitine and Long-Chain Acylcarnitines are Positively Correlated with Ambulatory Blood Pressure in Humans: The SABPA Study

The prevalence of hypertension in sub-Saharan Africa is increasing rapidly, and treatment remains challenging. Although the use of l-carnitine in treatment has received much attention, studies reporting on physiological l-carnitine levels in hypertensives are limited. Our aim was to determine physiological levels of l-carnitine and acylcarnitines in African and Caucasian men, and to investigate associations between ambulatory blood pressure (BP) and carnitine levels. Participants included 101 African and 101 Caucasian teachers. Ambulatory BP measurements were conducted, and l-carnitine and acylcarnitine levels determined. African men showed significantly higher systolic BP (p < 0.001), diastolic BP (p < 0.001) and l-carnitine levels (p = 0.01). In both ethnic groups, partial regression analyses revealed a positive association between BP and l-carnitine, although in Caucasians it was with systolic (r = 0.20, p = 0.045), and in Africans with diastolic BP (r = 0.23, p = 0.023). After adjusting for confounders, an independent positive association between systolic (R ² = 0.37, β = 0.12, p = 0.041) and diastolic BP (R ² = 0.39, β = 0.14, p = 0.018) and l-carnitine and long-chain acylcarnitines (R ² = 0.38, β = 0.17, p = 0.005 and R ² = 0.39, β = 0.15, p = 0.011) were found, independent of ethnicity. Physiological l-carnitine levels were not only higher in Africans than in Caucasians but also above the expected reference range. Despite promising results on l-carnitine (and its short-chain derivatives) in hypertension treatment regimens, our findings paradoxically show that elevated BP is significantly associated with higher physiological l-carnitine and long-chain acylcarnitine levels.     

Human scFv SIgA expressed on Lactococcus lactis as a vector for the treatment of mucosal disease

The gastrointestinal tract is a complex niche and the main port of entry of many pathogens that trigger a wide range of diseases like inflammatory bowel disease (IBD) and colon cancer. Antibodies are effective for treating such diseases, but a system capable of local delivery at the site of the pathology, thus avoiding systemic side effects, is not yet available. Here we report a novel recombinant scFvSIgA1 protein produced by Lactococcus lactis, anchored to the bacterial membrane, which retains its full immuno-recognizing potential. This scFv fragment employed was specific for a colon cancer epitope, epithelial glycoprotein protein-2 (EGP-2). Accordingly L. lactis expressing this chimeric protein was capable of binding cells expressing this epitope. Expression of specific antibodies on bacteria may allow local delivery of anticancer agents produced by such bacteria in conjunction with the antibody and provides a new avenue in the quest for targeted drug delivery.     

Sulphur removal in ironmaking and oxygen steelmaking

Sulphur removal in the ironmaking and oxygen steelmaking process is reviewed. A sulphur balance is made for the steelmaking process of Tata Steel IJmuiden, the Netherlands. There are four stages where sulphur can be removed: in the blast furnace (BF), during hot metal (HM) pretreatment, in the converter and during the secondary metallurgy (SM) treatment. For sulphur removal a low oxygen activity and a basic slag are required. In the BF typically 90% of the sulphur is removed; still, the HM contains about 0.03% of sulphur. Different HM desulphurisation processes are used worldwide. With co-injection or the Kanbara reactor, sulphur concentrations below 0.001% are reached. Basic slag helps desulphurisation in the converter. However, sulphur increase is not uncommon in the converter due to high oxygen activity and sulphur input via scrap and additions. For low sulphur concentrations SM desulphurisation, with a decreased oxygen activity and a basic slag, is always required.