Solid-state NMR study of stereocomplexes formed by enantiomeric star-shaped PEG-PLA copolymers in water

Solid-state NMR was applied to samples obtained by freeze-drying hydrogels of 1:1 (PEG65-NHCO-PLLA13)8/(PEG65-NHCO-PDLA13)8 or (PEG65-NHCO-PDLA13)8 only star block copolymers (where PEG, PLLA, and PDLA stand for poly(ethylene glycol), poly(l-lactide), and poly(d-lactide), respectively) in order to get insight into the different structural and dynamic properties of stereocomplexed poly(lactide) (PLA) aggregates with respect to single enantiomer ones responsible for the improved mechanical and degradation properties of the corresponding hydrogels. 13C MAS NMR experiments together with 13C relaxation time measurements indicated that the PLA domains in (PEG65-NHCO-PLLA13)8/(PEG65-NHCO-PDLA13)8 were highly crystalline, whereas those in (PEG65-NHCO-PDLA13)8 were mainly amorphous. On the basis of 1H relaxation and spin-diffusion experiments, similar average dimensions were determined for the PLA aggregates in the two samples. PLA stereocomplexation was found to strongly affect the conformational behavior of PEG chains. Under the assumption that freeze-drying preserves the structure of at least the PLA aggregates, the results obtained are of value for understanding self-aggregation of PEG–PLA star block copolymers in water

The SURgical PAtient Safety System (SURPASS) checklist optimizes timing of antibiotic prophylaxis

Background: Surgical site infection (SSI) is an adverse event in which a close relation between process of care and outcome has been demonstrated: administration of antibiotic prophylaxis decreases the risk of SSI. In our tertiary referral centre, a SURgical PAtient Safety System (SURPASS) checklist was developed and implemented. This multidisciplinary checklist covers the entire surgical pathway and includes, among other items, administration of antibiotic prophylaxis before induction of anaesthesia. The aim of this study was to determine the effect of SURPASS implementation on timing of antibiotic prophylaxis. Methods: A retrospective analysis was performed on two cohorts of patients: one cohort of surgical patients that underwent surgery before implementation of the checklist and a comparable cohort after implementation. The interval between administration of antibiotic prophylaxis and incision was compared between the two cohorts. Results: A total of 772 surgical procedures were included. More than half of procedures were gastro-intestinal; others were vascular, trauma and hernia repair procedures. After implementation, the checklist was used in 81.4 % of procedures. The interval between administration of antibiotic prophylaxis and incision increased from 23.9 minutes before implementation of SURPASS to 29.9 minutes after implementation (p = 0.047). In procedures where the checklist was used, the interval increased to 32.9 minutes (p = 0.004). The proportion of patients that did not receive antibiotics until after the incision decreased significantly. Conclusion: The use of the SURPASS checklist leads to better compliance with regard to the timing of antibiotic prophylaxis administration

Self-assembly and photo-cross-linking of eight-armed PEG-PTMC star block copolymers

Eight-armed poly(ethylene glycol)-poly(trimethylene carbonate) star block copolymers (PEG-(PTMC)8) linked by a carbamate group between the PEG core and the PTMC blocks were synthesized by the metal-free, HCl-catalyzed ring-opening polymerization of trimethylene carbonate using an amine-terminated eight-armed star PEG in dichloromethane. Although dye solubilization experiments, nuclear magnetic resonance spectroscopy, and dynamic light scattering clearly indicated the presence of aggregates in aqueous dispersions of the copolymers, no physical gelation was observed up to high concentrations. PEG-(PTMC9)8 was end-group-functionalized using acryloyl chloride and photopolymerized in the presence of Irgacure 2959. When dilute aqueous dispersions of PEG-(PTMC9)8-Acr were UV irradiated, chemically cross-linked PEG-PTMC nanoparticles were obtained, whereas irradiation of more concentrated PEG-(PTMC9)8-Acr dispersions resulted in the formation of photo-cross-linked hydrogels. Their good mechanical properties and high stability against hydrolytic degradation make photo-cross-linked PEG-PTMC hydrogels interesting for biomedical applications such as matrices for tissue engineering and controlled drug delivery systems

LCDM predictions for galaxy protoclusters I: the relation between galaxies, protoclusters and quasars at z~6

Motivated by recent observational studies of the environment of z~6 QSOs, we have used the Millennium Run (MR) simulations to construct a very large (~20 deg^2) mock redshift survey of star-forming galaxies at z~6. We use this simulated survey to study the relation between density enhancements in the distribution of i-dropouts and Lya-emitters, and their relation to the most massive halos and protocluster regions at z~6. Our simulation predicts significant variations in surface density across the sky with some voids and filaments extending over scales of 1 degree, much larger than probed by current surveys. Approximately one third of all z~6 halos hosting i-dropouts brighter than z=26.5 mag (~M* at z=6) become part of z=0 galaxy clusters. i-dropouts associated with protocluster regions are found in regions where the surface density is enhanced on scales ranging from a few to several tens of arcminutes on the sky. We analyze two structures of i-dropouts and Lya-emitters observed with the Subaru Telescope and show that these structures must be the seeds of massive clusters-in-formation. In striking contrast, six z~6 QSO fields observed with HST show no significant enhancements in their i-dropout number counts. With the present data, we cannot rule out the QSOs being hosted by the most massive halos. However, neither can we confirm this widely used assumption. We conclude by giving detailed recommendations for the interpretation and planning of observations by current and future ground- and space based instruments that will shed new light on questions related to the large-scale structure at z~6.Comment: Accepted by MNRAS (19 pages, 20 figures, 2 tables). High resolution PDF available at http://www.mpa-garching.mpg.de/~overzier/overzierz6.pd

The Observed and Predicted Spatial Distribution of Milky Way Satellite Galaxies

We review evidence that the census of Milky Way satellites similar to those known may be incomplete at low latitude due to obscuration and in the outer halo due to a decreasing sensitivity to dwarf satellites with distance. We evaluate the possible impact that incompleteness has on comparisons with substructure models by estimating corrections to the known number of dwarfs using empirical and theoretical models. If we assume that the true distribution of Milky Way satellites is uniform with latitude, then we estimate a 33% incompleteness in the total number of dwarfs due to obscuration at low latitude. Similarly, if we suppose that the radial distribution of Milky Way satellites matches that of M31, or that of the oldest sub-halos or the most massive sub-halos in a simulation, we estimate a total number of Milky Way dwarfs ranging from 1 -- 3 times the known population. Although the true level of incompleteness is quite uncertain, the fact that our extrapolations yield average total numbers of MW dwarfs that are realistically 1.5 -- 2 times the known population, shows that incompleteness needs to be taken seriously when comparing to models of dwarf galaxy formation. Interestingly, the radial distribution of the oldest sub-halos in a Lambda+CDM simulation of a Milky Way-like galaxy possess a close match to the observed distribution of M31's satellites, which suggests that reionization may be an important factor controlling the observability of sub-halos. We also assess the prospects for a new SDSS search for Milky Way satellites to constrain the possible incompleteness in the outer halo.Comment: 9 pages, 7 figures. Replaced with MNRAS accepted versio

Detecting gravitationally lensed population III galaxies with the Hubble Space Telescope and the James Webb Space Telescope

Small galaxies consisting entirely of population III (pop III) stars may form at high redshifts, and could constitute one of the best probes of such stars. Here, we explore the prospects of detecting gravitationally lensed pop III galaxies behind the galaxy cluster J0717.5+3745 (J0717) with both the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST). By projecting simulated catalogs of pop III galaxies at z~7-15 through the J0717 magnification maps, we estimate the lensed number counts as a function of flux detection threshold. We find that the ongoing HST survey CLASH, targeting a total of 25 galaxy clusters including J0717, potentially could detect a small number of pop III galaxies if ~1% of the baryons in these systems have been converted into pop III stars. Using JWST exposures of J0717, this limit can be pushed to ~0.1% of the baryons. Ultra-deep JWST observations of unlensed fields are predicted to do somewhat worse, but will be able to probe pop III galaxies with luminosities intermediate between those detectable in HST/CLASH and in JWST observations of J0717. We also explain how current measurements of the galaxy luminosity function at z=7-10 can be used to constrain pop III galaxy models with very high star formation efficiencies (~10% of the baryons converted into pop III stars).Comment: 14 pages, 7 figures, accepted for publication in MNRAS (v.2: presentation improved, but only minor changes in overall results

Feasibility of a standardized family participation programme in the intensive care unit: A pilot survey study

Aim: To assess the feasibility and applicability of a standardized programme to facilitate family participation in essential care activities in the intensive care unit. Design: Pilot study with a cross-sectional survey design. Methods: A standardized programme to facilitate family participation in essential nursing care activities was implemented in intensive care units of three hospitals in the Netherlands from November 2018 until March 2019. The feasibility and applicability of the programme were assessed with surveys of the patients, relatives and healthcare providers. Results: Three intensive care units successfully implemented the standardized programme. Three patients, ten relatives and 37 healthcare providers responded to the surveys. Patients appreciated family participation and recognized that their relatives liked to participate. Relatives appreciated being able to do something for the patient (80%) and to participate in essential care activities (60%). The majority of relatives (60%) felt they had sufficient knowledge and skills to participate and did not feel obliged nor uncomfortable. Healthcare providers felt they were trained adequately and motivated to apply family participation; application was perceived as easy, clear and relatively effortless according to the majority. According to 68% of the healthcare providers, most relatives were perceived to be capable of learning to participate in essential care activities. Some healthcare providers felt uncertain about the patient's wishes regarding family participation, with some indicating the behaviours of relatives and patients discouraged them from offering family participation. Use of a standardized programme to facilitate family participation in essential care activities in the intensive care unit seems feasible and applicable as determined by relatives and healthcare providers

Constraining Dynamical Dark Energy Models through the Abundance of High-Redshift Supermassive Black Holes

We compute the number density of massive Black Holes (BHs) at the centre of galaxies at z=6 in different Dynamical Dark Energy (DDE) cosmologies, and compare it with existing observational lower limits, to derive constraints on the evolution of the Dark Energy equation of state parameter w. Our approach only assumes the canonical scenario for structure formation from the collapse of overdense regions of the Dark Matter dominated primordial density field on progressively larger scales; the Black Hole accretion and merging rate have been maximized in the computation so as to obtain robust constraints on w and on its look-back time derivative w_a. Our results provide independent constraints complementary to those obtained by combining Supernovae, Cosmic Microwave Background and Baryonic Acoustic Oscillations; while the latter concern combinations of w_0 and w_a leaving the time evolution of the state parameter w_a highly unconstrained, the BH abundance mainly provide upper limits on w_a, only weakly depending on w_0. Combined with the existing constraints, our results significantly restrict the allowed region in DDE parameter space, ruling out DDE models not providing cosmic time and fast growth factor large enough to allow for the building up of the observed abundance of BHs; in particular, models with -1.2 \leq w_0 \leq -1 and positive redshift evolution w_a > 0.8 - completely consistent with previous constraints - are strongly disfavoured by our independent constraints from BH abundance. Such range of parameters corresponds to "Quintom" DDE models, with w crossing -1 starting from larger values.Comment: 19 pages, 6 figures, accepted to MNRA

Computational Identification of Phospho-Tyrosine Sub-Networks Related to Acanthocyte Generation in Neuroacanthocytosis

Acanthocytes, abnormal thorny red blood cells (RBC), are one of the biological hallmarks of neuroacanthocytosis syndromes (NA), a group of rare hereditary neurodegenerative disorders. Since RBCs are easily accessible, the study of acanthocytes in NA may provide insights into potential mechanisms of neurodegeneration. Previous studies have shown that changes in RBC membrane protein phosphorylation state affect RBC membrane mechanical stability and morphology. Here, we coupled tyrosine-phosphoproteomic analysis to topological network analysis. We aimed to predict signaling sub-networks possibly involved in the generation of acanthocytes in patients affected by the two core NA disorders, namely McLeod syndrome (MLS, XK-related, Xk protein) and chorea-acanthocytosis (ChAc, VPS13A-related, chorein protein). The experimentally determined phosphoproteomic data-sets allowed us to relate the subsequent network analysis to the pathogenetic background. To reduce the network complexity, we combined several algorithms of topological network analysis including cluster determination by shortest path analysis, protein categorization based on centrality indexes, along with annotation-based node filtering. We first identified XK- and VPS13A-related protein-protein interaction networks by identifying all the interactomic shortest paths linking Xk and chorein to the corresponding set of proteins whose tyrosine phosphorylation was altered in patients. These networks include the most likely paths of functional influence of Xk and chorein on phosphorylated proteins. We further refined the analysis by extracting restricted sets of highly interacting signaling proteins representing a common molecular background bridging the generation of acanthocytes in MLS and ChAc. The final analysis pointed to a novel, very restricted, signaling module of 14 highly interconnected kinases, whose alteration is possibly involved in generation of acanthocytes in MLS and ChAc