Convergence Radii for Eigenvalues of Tri--diagonal Matrices

Consider a family of infinite tri--diagonal matrices of the form $L+ zB,$ where the matrix $L$ is diagonal with entries $L_{kk}= k^2,$ and the matrix $B$ is off--diagonal, with nonzero entries $B_{k,{k+1}}=B_{{k+1},k}= k^\alpha, 0 \leq \alpha < 2.$ The spectrum of $L+ zB$ is discrete. For small $|z|$ the $n$-th eigenvalue $E_n (z), E_n (0) = n^2,$ is a well--defined analytic function. Let $R_n$ be the convergence radius of its Taylor's series about $z= 0.$ It is proved that $$ R_n \leq C(\alpha) n^{2-\alpha} \quad \text{if} 0 \leq \alpha <11/6.$

Optimal Dividend Payments for the Piecewise-Deterministic Poisson Risk Model

This paper considers the optimal dividend payment problem in piecewise-deterministic compound Poisson risk models. The objective is to maximize the expected discounted dividend payout up to the time of ruin. We provide a comparative study in this general framework of both restricted and unrestricted payment schemes, which were only previously treated separately in certain special cases of risk models in the literature. In the case of restricted payment scheme, the value function is shown to be a classical solution of the corresponding HJB equation, which in turn leads to an optimal restricted payment policy known as the threshold strategy. In the case of unrestricted payment scheme, by solving the associated integro-differential quasi-variational inequality, we obtain the value function as well as an optimal unrestricted dividend payment scheme known as the barrier strategy. When claim sizes are exponentially distributed, we provide easily verifiable conditions under which the threshold and barrier strategies are optimal restricted and unrestricted dividend payment policies, respectively. The main results are illustrated with several examples, including a new example concerning regressive growth rates.Comment: Key Words: Piecewise-deterministic compound Poisson model, optimal stochastic control, HJB equation, quasi-variational inequality, threshold strategy, barrier strateg

Patients’ and healthcare professionals’ perceptions of blood transfusion

Background: Blood transfusions are frequently provided to patients at risk of severe bleeding or on a repeated basis for patients with anaemia or blood disorders. The treatment perceptions literature indicates that perceptions influence how patients cope with their conditions and adhere to treatment. Healthcare professionals’ (HCPs’) perceptions are likely to influence shared decision-making and their practice. However, how patients and HCPs perceive blood transfusions, and how this may vary across patient groups, is unclear. Objectives: This research aimed to explore patients’ and HCPs’ perceptions of blood transfusion. Specific research questions were: 1) which perceptions of transfusion are reported by patients and HCPs in the literature? 2) to what extent do themes of patients’ perceptions correspond with the broader treatment perceptions literature? 3) what are repeatedly transfused haematology patients’ and HCPs’ perceptions of transfusion? 4) to what extent do HCPs recognise patients’ reported perceptions in their practice and are practice changes to improve patients’ experiences required? Methods: This was a mixed-methods programme of research involving three studies: Study 1: A systematic review of patients’ and HCPs’ perceptions of blood transfusion and development of a conceptual model of blood transfusion perceptions. This was followed by a theoretical mapping exercise to compare the model to existing treatment perceptions frameworks. Study 2: A semi-structured interview study with 14 haematology patients and 14 HCPs about their perceptions of blood transfusion. Study 3: A focus group (n=3) and questionnaire study of 19 HCPs’ views of haematology patients’ perceptions and their views about potential service improvement strategies, subsequently mapped to a behaviour change framework (Behaviour Change Wheel). HCPs’ reported constraints and enablers to implementing these strategies were mapped to the Theoretical Domains Framework (TDF) of behaviour change. Results: Study 1: 41 papers reporting patients’ and HCPs’ perceptions were included in the systematic review (15 patient studies, 26 HCPs). Transfusion was perceived as carrying low to moderate risk, but risk perceptions and negative emotions were associated with the use and consideration of transfusion alternatives. The data were synthesised into six constructs to form a conceptual model: ‘Safety/risk,’ ‘Negative emotions’, ‘Alternatives’, ‘Health benefits’, ‘Necessity’ and ‘Decision making’. Theoretical mapping confirmed these constructs as broadly consistent with constructs from existing treatment perceptions frameworks and models. Study 2: Patients and HCPs reported views about the benefits of transfusion for haematology patients, yet some patients and HCPs reported concerns about the downsides of transfusion. ‘Organisational constraints’ were raised by HCPs about delivering transfusions in pressurised services and patients discussed the burden of receiving repeated transfusions. Study 3: 17 service improvement strategies were proposed, corresponding to seven BCW functions: (e.g. ‘Service provision’ (home transfusion), ‘Environmental restructuring’ (remote blood screening)). Constraints/enablers mapped to the TDF: (e.g. ‘Skills’ (HCP communication skills training), ‘Environmental context and resources’ (funding, time)). Potential techniques to address constraints and enablers included providing ‘Information about health consequences’ to address the domain, ‘Beliefs about consequences’. Conclusion: This research provides a theoretical and empirical overview of blood transfusion perceptions, including themes shared by patients and HCPs and themes that were unique to one of these groups. There is scope to more greatly involve patients in their transfusions where, in haematology, repeated and lengthy transfusion appointments place burden on patients. The conceptual models provide direction for such consultations. Interventions to enhance haematology patients’ experiences and to remediate service pressures can be developed further

Structure of the axonal surface recognition molecule neurofascin and its relationship to a neural subgroup of the immunoglobulin superfamily

The chick axon-associated surface glycoprotein neurofascin is implicated in axonal growth and fasciculation as revealed by antibody perturbation experiments. Here we report the complete cDNA sequence of neurofascin. It is composed of four structural elements: At the NH2 terminus neurofascin contains six Ig-like motifs of the C2 subcategory followed by four fibronectin type III (FNIII)-related repeats. Between the FNIII-like repeats and the plasma membrane spanning region neurofascin contains a domain 75-amino acid residues-long rich in proline, alanine and threonine which might be the target of extensive O-linked glycosylation. A transmembrane segment is followed by a 113-amino acid residues-long cytoplasmic domain. Sequence comparisons indicate that neurofascin is most closely related to chick Nr-CAM and forms with L1 (Ng-CAM) and Nr-CAM a subgroup within the vertebrate Ig superfamily. Sequencing of several overlapping cDNA probes reveals interesting heterogeneities throughout the neurofascin polypeptide. Genomic Southern blots analyzed with neurofascin cDNA clones suggest that neurofascin is encoded by a single gene and its pre-mRNA might be therefore alternatively spliced. Northern blot analysis with domain specific probes showed that neurofascin mRNAs of about 8.5 kb are expressed throughout development in embryonic brain but not in liver. Isolation of neurofascin by immunoaffinity chromatography results in several molecular mass components. To analyze their origin the amino-terminal sequences of several neurofascin components were determined. The NH2-terminal sequences of the 185, 160, and 110-135 kD components are all the same as the NH2 termini predicted by the cDNA sequence, whereas the other neurofascin components start with a sequence found in a putative alternatively spliced segment between the Ig- and FNIII-like part indicating that they are derived by proteolytic cleavage. A combination of enzymatic and chemical deglycosylation procedures and the analysis of peanut lectin binding reveals O- and N-linked carbohydrates on neurofascin components which might generate additional heterogeneity

Orientation dependence of the sticking probability of NO at Ni(100)

Fecher GH, Volkmer M, Pawlitzky B, Böwering N, Heinzmann U. Orientation dependence of the sticking probability of NO at Ni(100). Vacuum. 1990;41(1-3):265-268

A short artificial antimicrobial peptide shows potential to prevent or treat bone infections.

Infection of bone is a severe complication due to the variety of bacteria causing it, their resistance against classical antibiotics, the formation of a biofilm and the difficulty to eradicate it. Antimicrobial peptides (AMPs) are naturally occurring peptides and promising candidates for treatment of joint infections. This study aimed to analyze the effect of short artificial peptides derived from an optimized library regarding (1) antimicrobial effect on different bacterial species, (2) efficacy on biofilms, and (3) effect on osteoblast‑like cells. Culturing the AMP-modifications with Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus (including clinical isolates of MRSA and MSSA) and Staphylococcus epidermidis identified one candidate that was most effective against all bacteria. This AMP was also able to reduce biofilm as demonstrated by FISH and microcalorimetry. Osteoblast viability and differentiation were not negatively affected by the AMP. A cation concentration comparable to that physiologically occurring in blood had almost no negative effect on AMP activity and even with 10% serum bacterial growth was inhibited. Bacteria internalized into osteoblasts were reduced by the AMP. Taken together the results demonstrate a high antimicrobial activity of the AMP even against bacteria incorporated in a biofilm or internalized into cells without harming human osteoblasts

Impact of primary formaldehyde on air pollution in the Mexico City Metropolitan Area

Formaldehyde (HCHO) is a radical source that plays an important role in urban atmospheric chemistry and ozone formation. The Mexico City Metropolitan Area (MCMA) is characterized by high anthropogenic emissions of HCHO (primary HCHO), which together with photochemical production of HCHO from hydrocarbon oxidation (secondary HCHO), lead to high ambient HCHO levels. The CAMx chemical transport model was employed to evaluate the impact of primary HCHO on its ambient concentration, on the ROx radical budget, and on ozone (O3) formation in the MCMA. Important radical sources, including HCHO, HONO, and O3-olefin reactions, were constrained by measurements from routine observations of the local ambient air monitoring network and the MCMA-2003 field campaign. Primary HCHO was found not only to contribute significantly to the ambient HCHO concentration, but also to enhance the radical budget and O3 production in the urban atmosphere of the MCMA. Overall in the urban area, total daytime radical production is enhanced by up to 10% and peak O3 concentration by up to 8%; moreover primary HCHO tends to make O3 both production rates and ambient concentration peak half an hour earlier. While primary HCHO contributes predominantly to the ambient HCHO concentration between nighttime and morning rush hours, significant influence on the radical budget and O3 production starts early in the morning, peaks at mid-morning and is sustained until early afternoon.Mexican Metropolitan Commission of EnvironmentNational Science Foundation (U.S.) (ATM-0528227

A pentapeptide as minimal antigenic determinant for MHC class I-restricted T lymphocytes

Peptides that are antigenic for T lymphocytes are ligands for two receptors, the class I or II glycoproteins that are encoded by genes in the major histocompatibility complex, and the idiotypic / chain T-cell antigen receptor1–9. That a peptide must bind to an MHC molecule to interact with a T-cell antigen receptor is the molecular basis of the MHC restriction of antigen-recognition by T lymphocytes10,11. In such a trimolecular interaction the amino-acid sequence of the peptide must specify the contact with both receptors: agretope residues bind to the MHC receptor and epitope residues bind to the T-cell antigen receptor12,13. From a compilation of known antigenic peptides, two algorithms have been proposed to predict antigenic sites in proteins. One algorithm uses linear motifs in the sequence14, whereas the other considers peptide conformation and predicts antigenicity for amphipathic -helices15,16. We report here that a systematic delimitation of an antigenic site precisely identifies a predicted pentapeptide motif as the minimal antigenic determinant presented by a class I MHC molecule and recognized by a cytolytic T lymphocyte clone

Socially sensitive lactation: Exploring the social context of breastfeeding

Many women report difficulties with breastfeeding and do not maintain the practice for as long as intended. Although psychologists and other researchers have explored some of the difficulties they experience, fuller exploration of the relational contexts in which breastfeeding takes place is warranted to enable more in-depth analysis of the challenges these pose for breastfeeding women. The present paper is based on qualitative data collected from 22 first-time breastfeeding mothers through two phases of interviews and audio-diaries which explored how the participants experienced their relationships with significant others and the wider social context of breastfeeding in the first five weeks postpartum. Using a thematic analysis informed by symbolic interactionism, we develop the overarching theme of ‘Practising socially sensitive lactation’ which captures how participants felt the need to manage tensions between breastfeeding and their perceptions of the needs, expectations and comfort of others. We argue that breastfeeding remains a problematic social act, despite its agreed importance for child health. Whilst acknowledging the limitations of our sample and analytic approach, we suggest ways in which perinatal and public health interventions can take more effective account of the social challenges of breastfeeding in order to facilitate the health and psychological well-being of mothers and their infants

Blood transfusion in haematology: A qualitative exploration of patients’ and healthcare professionals’ perceptions

Objectives Repeated blood transfusions are indicated for the management of patients with cancer or blood disorders. Patients’ perceptions about transfusions may be associated with decision-making and coping, which has been under-explored in the haematology context. This study therefore aimed to explore haematology transfusion patients’ and HCPs’ perceptions of blood transfusion, drawing on theory and previously identified themes of transfusion perceptions. Design Semi-structured interview study with 14 adult blood transfusion patients and 14 HCPs (consultants, registrars, nurses) at two UK haematology units. Methods Patient- and HCP-tailored topic guides were developed based on themes of blood transfusion perceptions identified in a systematic review: ‘Health benefits’, ‘Safety/risk’, ‘Negative emotions’, ‘Alternatives’ ‘Decision making’ and ‘Necessity’. Transcripts were analysed using deductive and thematic analysis. Patient and HCP themes were compared using triangulation methods. Conceptual models (one for patients, one for HCPs) specific to haematology portraying the association between themes were developed. Results Findings for patients and HCPs converged with transfusion reported as beneficial for patients, who were largely involved in the decision-making. Both groups also reported concerns about transfusion, including iron-overload, allergic reactions and challenges to deliver transfusions in time-pressurized services. Themes in the conceptual models included patient ‘Burden’ of receiving repeated transfusions and ‘Supportive relationships’, reflective of patients’ positive interactions with other patients and HCPs in the haematology unit. Conclusion Despite the challenges for patients receiving repeated transfusions, convergent perceptions suggest a shared understanding of patients’ transfusion experiences. Identified challenges could inform ways to improve transfusion services and patients’ experiences