Imprints of dark energy on cosmic structure formation: II) Non-Universality of the halo mass function

The universality of the halo mass function is investigated in the context of dark energy cosmologies. This widely used approximation assumes that the mass function can be expressed as a function of the matter density omega_m and the rms linear density fluctuation sigma only, with no explicit dependence on the properties of dark energy or redshift. In order to test this hypothesis we run a series of 15 high-resolution N-body simulations for different cosmological models. These consists of three LCDM cosmologies best fitting WMAP-1, 3 and 5 years data, and three toy-models characterized by a Ratra-Peebles quintessence potential with different slopes and amounts of dark energy density. These toy models have very different evolutionary histories at the background and linear level, but share the same sigma8 value. For each of these models we measure the mass function from catalogues of halos identified in the simulations using the Friend-of-Friend (FoF) algorithm. We find redshift dependent deviations from a universal behaviour, well above numerical uncertainties and of non-stochastic origin, which are correlated with the linear growth factor of the investigated cosmologies. Using the spherical collapse as guidance, we show that such deviations are caused by the cosmology dependence of the non-linear collapse and virialization process. For practical applications, we provide a fitting formula of the mass function accurate to 5 percents over the all range of investigated cosmologies. We also derive an empirical relation between the FoF linking parameter and the virial overdensity which can account for most of the deviations from an exact universal behavior. Overall these results suggest that the halo mass function contains unique cosmological information since it carries a fossil record of the past cosmic evolution.Comment: 21 pages, 19 figures, 5 tables, published in MNRAS. Paper I: arXiv:0903.549

Imprints of dynamical dark energy on weak-lensing measurements

We show that simple models of scalar-field dark energy leave a generic enhancement in the weak-lensing power spectrum when compared to the LCDM prediction. In particular, we calculate the linear-scale enhancement in the convergence (or cosmic-shear) power spectrum for two best-fit models of scalar-field dark energy, namely, the Ratra-Peebles and SUGRA-type quintessence. Our calculations are based on linear perturbation theory, using gauge-invariant variables with carefully defined adiabatic initial conditions. We find that geometric effects enhance the lensing power spectrum on a broad range of scales, whilst the clustering of dark energy gives rise to additional power on large scales. The dark-energy power spectrum for these models are also explicitly obtained. On degree scales, the total enhancement may be as large as 30-40% for sources at redshift ~1. We argue that there are realistic prospects for detecting such an enhancement using the next generation of large telescopes.Comment: 10 pages, 8 figures, replacement matches version published in MNRA

A pseudo feedback-based annotated TF-IDF technique for dynamic crypto-ransomware pre-encryption boundary delineation and features extraction

The cryptography employed against user files makes the effect of crypto-ransomware attacks irreversible even after detection and removal. Thus, detecting such attacks early, i.e. during pre-encryption phase before the encryption takes place is necessary. Existing crypto-ransomware early detection solutions use a fixed time-based thresholding approach to determine the pre-encryption phase boundaries. However, the fixed time thresholding approach implies that all samples start the encryption at the same time. Such assumption does not necessarily hold for all samples as the time for the main sabotage to start varies among different crypto-ransomware families due to the obfuscation techniques employed by the malware to change its attack strategies and evade detection, which generates different attack behaviors. Additionally, the lack of sufficient data at the early phases of the attack adversely affects the ability of feature extraction techniques in early detection models to perceive the characteristics of the attacks, which, consequently, decreases the detection accuracy. Therefore, this paper proposes a Dynamic Pre-encryption Boundary Delineation and Feature Extraction (DPBD-FE) scheme that determines the boundary of the pre-encryption phase, from which the features are extracted and selected more accurately. Unlike the fixed thresholding employed by the extant works, DPBD-FE tracks the pre-encryption phase for each instance individually based on the first occurrence of any cryptography-related APIs. Then, an annotated Term Frequency-Inverse Document Frequency (aTF-IDF) technique was utilized to extract the features from runtime data generated during the pre-encryption phase of crypto-ransomware attacks. The aTF-IDF overcomes the challenge of insufficient attack patterns during the early phases of the attack lifecycle. The experimental evaluation shows that DPBD-FE was able to determine the pre-encryption boundaries and extract the features related to this phase more accurately compared to related works

Laparoscopy in management of appendicitis in high-, middle-, and low-income countries: a multicenter, prospective, cohort study.

BACKGROUND: Appendicitis is the most common abdominal surgical emergency worldwide. Differences between high- and low-income settings in the availability of laparoscopic appendectomy, alternative management choices, and outcomes are poorly described. The aim was to identify variation in surgical management and outcomes of appendicitis within low-, middle-, and high-Human Development Index (HDI) countries worldwide. METHODS: This is a multicenter, international prospective cohort study. Consecutive sampling of patients undergoing emergency appendectomy over 6 months was conducted. Follow-up lasted 30 days. RESULTS: 4546 patients from 52 countries underwent appendectomy (2499 high-, 1540 middle-, and 507 low-HDI groups). Surgical site infection (SSI) rates were higher in low-HDI (OR 2.57, 95% CI 1.33-4.99, p = 0.005) but not middle-HDI countries (OR 1.38, 95% CI 0.76-2.52, p = 0.291), compared with high-HDI countries after adjustment. A laparoscopic approach was common in high-HDI countries (1693/2499, 67.7%), but infrequent in low-HDI (41/507, 8.1%) and middle-HDI (132/1540, 8.6%) groups. After accounting for case-mix, laparoscopy was still associated with fewer overall complications (OR 0.55, 95% CI 0.42-0.71, p < 0.001) and SSIs (OR 0.22, 95% CI 0.14-0.33, p < 0.001). In propensity-score matched groups within low-/middle-HDI countries, laparoscopy was still associated with fewer overall complications (OR 0.23 95% CI 0.11-0.44) and SSI (OR 0.21 95% CI 0.09-0.45). CONCLUSION: A laparoscopic approach is associated with better outcomes and availability appears to differ by country HDI. Despite the profound clinical, operational, and financial barriers to its widespread introduction, laparoscopy could significantly improve outcomes for patients in low-resource environments. TRIAL REGISTRATION: NCT02179112

Recycling aluminium AA6061 chips with reinforced boron carbide (B4C) and zirconia (ZrO2) particles via hot extrusion

Compared to the recycling process by remelting, hot extrusion significantly reduces the energy consumption and CO2 emission and ensures good mechanical and microstructural properties. This study investigates the effects of reinforcing aluminium AA6061 chips with mixed boron carbide (B4C) and zirconia (ZrO2) particles by employing a design of experiment (DOE) under 550 °C processing temperature and three hours preheating time. The findings showed that compressive strength (CS) and hardness increased with up to 5% added particles, and beyond 5%, the yielded values decreased because of materials agglomeration. However, the decreasing density was dependent on the addition of ZrO2 particles. The distribution of particles with different volume fractions of mixed particles was investigated by employing SEM, AFM, and EDS tests. Thus, the process can produce a net shape structure that utilises material-bonding consolidation to provide sufficient support to reuse the recovered materials in engineering applications, such as in the automotive industry

Imprints of Dark Energy on Cosmic Structure Formation I) Realistic Quintessence Models and the Non-Linear Matter Power Spectrum

Dark energy as a quintessence component causes a typical modification of the background cosmic expansion, which in addition to its clustering properties, can leave a potentially distinctive signature on large scale structures. Many previous studies have investigated this topic, particularly in relation to the non-linear regime of structure formation. However, no careful pre-selection of viable quintessence models with high precision cosmological data was performed. Here we show that this has led to a misinterpretation (and underestimation) of the imprint of quintessence on the distribution of large scale structures. To this purpose we perform a likelihood analysis of the combined Supernova Ia UNION dataset and WMAP5-years data to identify realistic quintessence models. Differences from the vanilla LambdaCDM are especially manifest in the predicted amplitude and shape of the linear matter power spectrum, though these remain within the uncertainties of the SDSS data. We use these models as benchmark for studying the clustering properties of dark matter halos by performing a series of high resolution N-body simulations. We find that realistic quintessence models allow for relevant differences of the dark matter distribution with the respect to the LambdaCDM scenario well into the non-linear regime, with deviations up to 40% in the non-linear power spectrum. Such differences are shown to depend on the nature of DE, as well as the scale and epoch considered. At small scales (k~1-5 h Mpc^{-1}, depending on the redshift) the structure formation process is about 20% more efficient than in LambdaCDM. We show that these imprints are a specific record of the cosmic structure formation history in DE cosmologies and therefore cannot be accounted in standard fitting functions of the non-linear matter power spectrum.Comment: 24 pages, 11 figures. Higher resolution paper available at http://cp3.phys.ucl.ac.be/upload/papers/astro-ph-0903.5490.ps (ps) and http://cp3.phys.ucl.ac.be/upload/papers/astro-ph-0903.5490.pdf (pdf). v2: New discussion on the non-linear power spectrum at small scales. v3: same as v2 with corrected references. Matches version to appear in MNRA

Immunotoxicity of polystyrene nanoplastics in different hemocyte subpopulations of Mytilus galloprovincialis

Plastic represents 60-80% of litter in the ocean. Degradation of plastic to small fragments leads to the formation of microplastics (MPs <5mm) and nanoplastics (NPs <1 mu m). One of the most widely used and representative plastics found in the ocean is polystyrene (PS). Among marine organisms, the immune system of bivalves is recognized as suitable to assess nanomaterial toxicity. Hemocyte subpopulations [R1 (large granular cells), R2 (small semi-granular cells) and R3 (small agranular or hyaline cells)] of Mytilus galloprovincialis are specialized in particular tasks and functions. The authors propose to examine the effects of different sizes (50 nm, 100 nm and 1 mu m) PS NPs on the different immune cells of mussels when they were exposed to (1 and 10mg.L-1) of PS NPs. The most noteworthy results found in this work are: (i) 1 mu m PS NPs provoked higher immunological responses with respect to 50 and 100nm PS NPs, possibly related to the higher stability in size and shape in hemolymph serum, (ii) the R1 subpopulation was the most affected with respect to R2 and R3 concerning immunological responses and (iii) an increase in the release of toxic radicals, apoptotic signals, tracking of lysosomes and a decrease in phagocytic activity was found in R1

cDNA Immunization of Mice with Human Thyroglobulin Generates Both Humoral and T Cell Responses: A Novel Model of Thyroid Autoimmunity

Thyroglobulin (Tg) represents one of the largest known self-antigens involved in autoimmunity. Numerous studies have implicated it in triggering and perpetuating the autoimmune response in autoimmune thyroid diseases (AITD). Indeed, traditional models of autoimmune thyroid disease, experimental autoimmune thyroiditis (EAT), are generated by immunizing mice with thyroglobulin protein in conjunction with an adjuvant, or by high repeated doses of Tg alone, without adjuvant. These extant models are limited in their experimental flexibility, i.e. the ability to make modifications to the Tg used in immunizations. In this study, we have immunized mice with a plasmid cDNA encoding the full-length human Tg (hTG) protein, in order to generate a model of Hashimoto's thyroiditis which is closer to the human disease and does not require adjuvants to breakdown tolerance. Human thyroglobulin cDNA was injected and subsequently electroporated into skeletal muscle using a square wave generator. Following hTg cDNA immunizations, the mice developed both B and T cell responses to Tg, albeit with no evidence of lymphocytic infiltration of the thyroid. This novel model will afford investigators the means to test various hypotheses which were unavailable with the previous EAT models, specifically the effects of hTg sequence variations on the induction of thyroiditis

Pooled analysis of who surgical safety checklist use and mortality after emergency laparotomy

Background: The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods: In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results: Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89⋅6 per cent) compared with that in countries with a middle (753 of 1242, 60⋅6 per cent; odds ratio (OR) 0⋅17, 95 per cent c.i. 0⋅14 to 0⋅21, P &lt; 0⋅001) or low (363 of 860, 42⋅2 percent; OR 0⋅08, 0⋅07 to 0⋅10, P &lt; 0⋅001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference −9⋅4 (95 per cent c.i. −11⋅9 to −6⋅9) per cent; P &lt; 0⋅001), but the relationship was reversed in low-HDI countries (+12⋅1 (+7⋅0 to +17⋅3) per cent; P &lt; 0⋅001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0⋅60, 0⋅50 to 0⋅73; P &lt; 0⋅001). The greatest absolute benefit was seen for emergency surgery in low-and middle-HDI countries. Conclusion: Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries