Program Calculation Properties of Continuous Algebras

Defining data types as initial algebras, or dually as final co-algebras, is beneficial, if not indispensible, for an algebraic calculus for program construction, in view of the nice equational properties that then become available. It is not hard to render finite lists as an initial algebra and, dually, infinite lists as a final co-algebra. However, this would mean that there are two distinct data types for lists, and then a program that is applicable to both finite and infinite lists is not possible, and arbitrary recursive definitions are not allowed. We prove the existence of algebras that are both initial in one category of algebras and final in the closely related category of co-algebras, and for which arbitrary (continuous) fixed point definitions ("recursion") do have a solution. Thus there is a single data type that comprises both the finite and the infinite lists. The price to be paid, however, is that partiality (of functions and values) is unavoidable. \ud We derive, for any such data type, various laws that are useful for an algebraic calculus of programs

Coordination of Axial Trunk Rotations During Gait in Low Back Pain. A Narrative Review

Chronic low back pain patients have been observed to show a reduced shift of thorax-pelvis relative phase towards out-of-phase movement with increasing speed compared to healthy controls. Here, we review the literature on this phase shift in patients with low back pain and we analyze the results presented in literature in view of the theoretical motivations to assess this phenomenon. Initially, based on the dynamical systems approach to movement coordination, the shift in thorax-pelvis relative phase with speed was studied as a self-organizing transition. However, the phase shift is gradual, which does not match a self-organizing transition. Subsequent emphasis in the literature therefore shifted to a motivation based on biomechanics. The change in relative phase with low back pain was specifically linked to expected changes in trunk stiffness due to ‘guarded behavior’. We found that thorax-pelvis relative phase is affected by several interacting factors, including active drive of thorax rotation through trunk muscle activity, stride frequency and the magnitude of pelvis rotations. Large pelvis rotations and high stride frequency observed in low back pain patients may contribute to the difference between patients and controls. This makes thorax-pelvis relative phase a poor proxy of trunk stiffness. In conclusion, thorax-pelvis relative phase cannot be considered as a collective variable reflecting the orderly behaviour of a complex underlying system, nor is it a marker of specific changes in trunk biomechanics. The fact that it is affected by multiple factors may explain the considerable between-subject variance of this measure in low back pain patients and healthy controls alike

Ex Situ Dual Hypothermic Oxygenated Machine Perfusion for Human Split Liver Transplantation

Liver splitting allows the opportunity to share a deceased graft between 2 recipients but remains underutilized. We hypothesized that liver splitting during continuous dual hypothermic oxygenated machine perfusion (DHOPE) is feasible, with shortened total cold ischemia times and improved logistics. Here, we describe a left lateral segment (LLS) and extended right lobe (ERL) liver split procedure during continuous DHOPE preservation with subsequent transplantation at 2 different centers. Methods: After transport using static cold storage, a 51-year-old brain death donor liver underwent end-ischemic DHOPE. During DHOPE, the donor liver was maintained 106 kPa. An ex situ ERL/LLS split was performed with continuing DHOPE throughout the procedure to avoid additional ischemia time. Results: Total cold ischemia times for the LLS and ERL were 205 minutes and 468 minutes, respectively. Both partial grafts were successfully transplanted at 2 different transplant centers. Peak aspartate aminotransferase and alanine aminotransferase were 172 IU/L and 107 IU/L for the LLS graft, and 839 IU/L and 502 IU/L for the ERL graft, respectively. The recipient of the LLS experienced an episode of acute cellular rejection. The ERL transplantation was complicated by severe acute pancreatitis with jejunum perforation requiring percutaneous drainage and acute cellular rejection. No device-related adverse events were observed. Conclusions: Liver splitting during continuous DHOPE preservation is feasible, has the potential to substantially shorten cold ischemia time and may optimize transplant logistics. Therefore liver splitting with DHOPE can potentially improve utilization of split liver transplantation

Branched KLVFF tetramers strongly potentiate inhibition of beta-amyloid aggregation

The key pathogenic event in the onset of Alzheimer's disease (AD) is the aggregation of beta-amyloid (Abeta) peptides into toxic aggregates. Molecules that interfere with this process might act as therapeutic agents for the treatment of AD. The amino acid residues 16-20 (KLVFF) are known to be essential for the aggregation of Abeta. In this study, we have used a first-generation dendrimer as a scaffold for the multivalent display of the KLVFF peptide. The effect of four KLVFF peptides attached to the dendrimer (K(4)) on Abeta aggregation was compared to the effect of monomeric KLVFF (K(1)). Our data show that K(4) very effectively inhibits the aggregation of low-molecular-weight and protofibrillar Abeta(1-42) into fibrils, in a concentration-dependent manner, and much more potently than K(1). Moreover, we show that K(4) can lead to the disassembly of existing aggregates. Our data lead us to propose that conjugates that bear multiple copies of KLVFF might be useful as therapeutic agents for the treatment of Alzheimer's disease

A multicentre retrospective analysis on growth of residual hepatocellular adenoma after resection

Background & Aims: Hepatocellular adenoma (HCA) is a benign liver tumour that may require resection in select cases. The aim of this study was to the assess growth of residual HCA in the remnant liver and to advise on an evidence-based management strategy. Method: This multicentre retrospective cohort study included all patients with HCA who underwent surgery of HCA and had residual HCA in the remnant liver. Growth was defined as an increase of >20% in transverse diameter (RECIST criteria). Data on patient and HCA characteristics, diagnostic work-up, treatment and follow-up were documented and analysed. Results: A total of 134 patients were included, one male. At diagnosis, median age was 38yrs (IQR 30.0-44.0) and median BMI was 29.9 kg/m2 (IQR 24.6-33.3). After resection, median number of residual sites of HCA was 3 (IQR 2-6). Follow-up of residual HCA showed regression in 24.6%, stable HCA in 61.9% and growth of at least one lesion in 11.2%. Three patients (2.2%) developed new HCA that were not visible on imaging prior to surgery. Four patients (3%, one male) underwent an intervention as growth was progressive. No statistically significant differences in clinical characteristics were found between patients with growing residual or new HCA versus those with stable or regressing residual HCA. Conclusion: In patients with multiple HCA who undergo resection, growth of residual HCA is not uncommon but interventions are rarely needed as most lesions stabilize and do not show progressive growth. Surveillance is indicated when residual HCA show growth after resection, enabling intervention in case of progressive growth

A multicentre retrospective analysis on growth of residual hepatocellular adenoma after resection

Background & Aims: Hepatocellular adenoma (HCA) is a benign liver tumour that may require resection in select cases. The aim of this study was to the assess growth of residual HCA in the remnant liver and to advise on an evidence-based management strategy. Method: This multicentre retrospective cohort study included all patients with HCA who underwent surgery of HCA and had residual HCA in the remnant liver. Growth was defined as an increase of >20% in transverse diameter (RECIST criteria). Data on patient and HCA characteristics, diagnostic work-up, treatment and follow-up were documented and analysed. Results: A total of 134 patients were included, one male. At diagnosis, median age was 38yrs (IQR 30.0-44.0) and median BMI was 29.9 kg/m2 (IQR 24.6-33.3). After resection, median number of residual sites of HCA was 3 (IQR 2-6). Follow-up of residual HCA showed regression in 24.6%, stable HCA in 61.9% and growth of at least one lesion in 11.2%. Three patients (2.2%) developed new HCA that were not visible on imaging prior to surgery. Four patients (3%, one male) underwent an intervention as growth was progressive. No statistically significant differences in clinical characteristics were found between patients with growing residual or new HCA versus those with stable or regressing residual HCA. Conclusion: In patients with multiple HCA who undergo resection, growth of residual HCA is not uncommon but interventions are rarely needed as most lesions stabilize and do not show progressive growth. Surveillance is indicated when residual HCA show growth after resection, enabling intervention in case of progressive growth

Pretransplant sequential hypo- and normothermic machine perfusion of suboptimal livers donated after circulatory death using a hemoglobin-based oxygen carrier perfusion solution

Ex situ dual hypothermic oxygenated machine perfusion (DHOPE) and normothermic machine perfusion (NMP) of donor livers may have a complementary effect when applied sequentially. While DHOPE resuscitates the mitochondria and increases hepatic adenosine triphosphate (ATP) content, NMP enables hepatobiliary viability assessment prior to transplantation. In contrast to DHOPE, NMP requires a perfusion solution with an oxygen carrier, for which red blood cells (RBC) have been used in most series. RBC, however, have limitations and cannot be used cold. We, therefore, established a protocol of sequential DHOPE, controlled oxygenated rewarming (COR), and NMP using a new hemoglobin-based oxygen carrier (HBOC)-based perfusion fluid (DHOPE-COR-NMP trial, NTR5972). Seven livers from donation after circulatory death (DCD) donors, which were initially declined for transplantation nationwide, underwent DHOPE-COR-NMP. Livers were considered transplantable if perfusate pH and lactate normalized, bile production was >= 10 mL and biliary pH > 7.45 within 150 minutes of NMP. Based on these criteria five livers were transplanted. The primary endpoint, 3-month graft survival, was a 100%. In conclusion, sequential DHOPE-COR-NMP using an HBOC-based perfusion fluid offers a novel method of liver machine perfusion for combined resuscitation and viability testing of suboptimal livers prior to transplantation

A non-invasive imaging approach for improved assessments on the construction and the condition of historical knotted-pile carpets

The appraisal of the design and the weaving structure of Islamic knotted-pile carpets can tell plenty about the context in which they were produced, and the identification of signs of deterioration can help to establish their condition. These are often somewhat imprecise and laborious examinations, especially when considering carpets of large dimensions. Analytical methods that support these disciplines urge further exploration so that improved interpretations can be obtained. An interdisciplinary combination of art history, analytical science and textile conservation aimed, on the one hand, to improve the weaving examination of these complex textile objects – by considering the spin of threads and the ply of yarns; the knot count and density; and the weaving structure of warps, wefts and piles – and on the other, to help their condition assessment – by mapping of damaged areas, old repairs and contaminations. For this purpose, the possibilities and limitations of several non-invasive imaging techniques, namely transmitted, raking or incident visible, ultraviolet (UV) and infrared (IR) illumination through Visual Spectral Comparator (VSC), as well as conventional X-radiography, mammography and (micro) CT scanning, were assessed to support the conventional visual examination of the weaving details and present c