242 research outputs found
Modelling of a Wall Inlet in Numerical Simulation of Airflow in Livestock Buildings
Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a Technical Article from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 4 (2002): B. Bjerg, K. Svidt, S. Morsing, G. Zhang, and J.O. Johnson. Modelling of a Wall Inlet in Numerical Simulation of Airflow in Livestock Buildings. Vol. IV. March 2002
Obstacle Effects on Airflow and Containment Dispersion around a Naturally Ventilated Livestock Building
Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a Technical Paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 5 (2003): G. Zhang, A. Ikeguchi, J. Strom, S. Morsing, H. Takai, P. Ravn, and L. Okushima. Obstacle Effects on Airflow and Containment Dispersion around a Naturally Ventilated Livestock Building. Vol. V. December 2003
Clinical Characteristics of a Non-Alcoholic Fatty Liver Disease Population Across the Fibrosis Spectrum Measured by Magnetic Resonance Elastography: Analysis of Screening Data
Introduction: Non-alcoholic fatty liver disease (NAFLD), one of the most common liver diseases, is associated with liver-related complications and metabolic comorbidities. The phenotype is wide, ranging from simple steatosis to non-alcoholic steatohepatitis with advanced fibrosis. In this analysis of a phase 1 trial, clinical characteristics of screened subjects with NAFLD were studied according to the extent of fibrosis assessed using magnetic resonance elastography (MRE). Methods: One hundred ninety-four subjects with body mass index (BMI) of 25–40\ua0kg/m2 and suspected NAFLD were assessed by MRE and grouped by MRE thresholds as a proxy for fibrosis staging (groups 0–4). Data were summarized by group levels, and correlation analyses between MRE values and clinical parameters (including magnetic resonance imaging-proton density fat fraction) were performed. Results: Most subjects had MRE values in the lower range (groups 0–1; N = 148). Type 2 diabetes (T2D) and BMI > 35\ua0kg/m2 were more frequent in groups with higher than lower MRE values. Subjects in the highest MRE groups also tended to be older and have higher liver enzyme concentrations compared with lower MRE groups. No, or weak, correlations were found between MRE values and clinical parameters (all r values ≤ 0.45). Conclusions: There was considerable variation and overlap in clinical characteristics across the spectrum of liver stiffness. Although groups with high MRE values generally included more subjects with T2D and obesity, and had higher age and concentrations of liver enzymes, the clinical characteristics did not strongly correlate with MRE scores in this population. Trial Registration: Registered on Clinicaltrials.gov on November 29, 2017 (NCT03357380)
Modeling of air inlets in CFD prediction of airflow in ventilated animal houses
Abstract This study investigates different methods to model wall inlets in computational fluid dynamics (CFD) simulations of airflow in livestock rooms. The experiments were carried out in an 8.5 m long, 3 m high and 10.14 m wide test room equipped with a forced ventilation system. Four wall inlets were distributed symmetrically along an end wall 0.5 m beneath the ceiling. To obtain uniform and easily modeled boundary conditions the inlets were designed as rectangular frames with an elliptic profile in the contraction section following the ISO standard for a long-radius nozzle. Vertical and horizontal air speed profiles in the jets were measured with thermistor speed sensors at four distances from the inlets and an ultrasonic sensor was used for measurement of air velocity in the occupied zone close to the floor. CFD-simulations with the k-o turbulence model were carried out with a number of different grid constructions. Both measurement and CFD simulations showed that two different airflow patterns occurred in the test room. In airflow pattern 1 the jets beneath the ceiling turned towards the symmetry plane of the room and above the floor the air flowed away from the symmetry plane. In air flow pattern 2 the jets turned away from the symmetry plane and above the floor the air flowed towards the symmetry plane. The findings in this study indicate that assuming two dimensional (2-D) inlet conditions might be a useful way to simplify inlet boundary conditions and grid constructions for prediction of air flow in the occupied zone of livestock rooms with many wall inlets. However, more work must be done to evaluate this statement in other arrangements, including changed orientation and loca
National cohort of infants born before 24 gestational weeks showed increased survival rates but no improvement in neonatal morbidity
Aim: To describe survival and neonatal morbidities in infants born before 24\ua0weeks of gestation during a 12-year period. Methods: Data were retrieved from national registries and validated in medical files of infants born before 24\ua0weeks of gestation 2007–2018 in Sweden. Temporal changes were evaluated. Results: In 2007–2018, 282\ua0live births were recorded at 22\ua0weeks and 460 at 23\ua0weeks of gestation. Survival to discharge from hospital of infants born alive at 22 and 23\ua0weeks increased from 20% to 38% (p\ua0=\ua00.006) and from 45% to 67% (
DPRESS: Localizing estimates of predictive uncertainty
<p>Abstract</p> <p>Background</p> <p>The need to have a quantitative estimate of the uncertainty of prediction for QSAR models is steadily increasing, in part because such predictions are being widely distributed as tabulated values disconnected from the models used to generate them. Classical statistical theory assumes that the error in the population being modeled is independent and identically distributed (IID), but this is often not actually the case. Such inhomogeneous error (heteroskedasticity) can be addressed by providing an individualized estimate of predictive uncertainty for each particular new object <it>u</it>: the standard error of prediction <it>s</it><sub>u </sub>can be estimated as the non-cross-validated error <it>s</it><sub>t* </sub>for the closest object <it>t</it>* in the training set adjusted for its separation <it>d </it>from <it>u </it>in the descriptor space relative to the size of the training set.</p> <p><display-formula><graphic file="1758-2946-1-11-i1.gif"/></display-formula></p> <p>The predictive uncertainty factor <it>γ</it><sub>t* </sub>is obtained by distributing the internal predictive error sum of squares across objects in the training set based on the distances between them, hence the acronym: <it>D</it>istributed <it>PR</it>edictive <it>E</it>rror <it>S</it>um of <it>S</it>quares (DPRESS). Note that <it>s</it><sub>t* </sub>and <it>γ</it><sub>t*</sub>are characteristic of each training set compound contributing to the model of interest.</p> <p>Results</p> <p>The method was applied to partial least-squares models built using 2D (molecular hologram) or 3D (molecular field) descriptors applied to mid-sized training sets (<it>N </it>= 75) drawn from a large (<it>N </it>= 304), well-characterized pool of cyclooxygenase inhibitors. The observed variation in predictive error for the external 229 compound test sets was compared with the uncertainty estimates from DPRESS. Good qualitative and quantitative agreement was seen between the distributions of predictive error observed and those predicted using DPRESS. Inclusion of the distance-dependent term was essential to getting good agreement between the estimated uncertainties and the observed distributions of predictive error. The uncertainty estimates derived by DPRESS were conservative even when the training set was biased, but not excessively so.</p> <p>Conclusion</p> <p>DPRESS is a straightforward and powerful way to reliably estimate individual predictive uncertainties for compounds outside the training set based on their distance to the training set and the internal predictive uncertainty associated with its nearest neighbor in that set. It represents a sample-based, <it>a posteriori </it>approach to defining applicability domains in terms of localized uncertainty.</p
Corporate Social Responsibility Strategies of Spanish Listed Firms and Controlling Shareholders’ Representatives
This article aims at analyzing how controlling shareholders’ representatives on boards affect
corporate social responsibility (CSR) strategies (disclosing CSR matters) in Spain, a context
characterized by high ownership concentration, one-tier boards, little board independence, weak
legal protection for investors, and the presence of large shareholders, especially institutional
shareholders. Furthermore, among controlling shareholders’ representatives, we can distinguish
between those appointed by insurance companies and banks and those appointed by mutual funds,
investment funds, and pension funds. The effect of these categories of directors on CSR strategies
is, therefore, also analyzed. Our findings suggest that controlling shareholders’ representatives
have a positive effect on CSR strategies, as do directors appointed by investment funds, pension
funds, and mutual funds, while directors appointed by banks and insurance companies have no
impact on CSR strategies. This analysis offers new insights into the role played by certain types
of directors on CSR strategies
Magneto‐structural studies of paramagnetic metal cages
A central concern within the field of molecular magnetism has been the elucidation of magneto-structural
correlations. This thesis describes a variety of systems and endeavours to study the
relationship between structure and magnetic properties in these systems. The first body of work
(chapters 2 and 3) studies CrIII dimers, with the metal centres displaying a dialkoxo bridging moiety
and latterly an additional carboxylate bridge to direct the synthesis of ferromagnetic analogues. The
second section of work (chapters 4‐6) moves forward to the study of larger, heterometallic 3d‐3d
compounds, through the synthesis of a large family of Anderson type MIII
2MII
5 wheels and a
subsequent family of (VIVO)2MII
5 wheels.
Chapter 2 describes a series of di‐alkoxo bridged Cr(III) dimers, synthesised using the pyridine alcohol
ligands 2‐pyridinemethanol (hmpH) and 2‐pyridineethanol (hepH) as well as 2‐picolinic acid (picH).
The structures fall into four general categories and are of formula: [Cr2(OMe)2(pic)4],
[Cr2(hmp)2(pic)2X2] (where X = Cl, Br), [Cr2(L)2Cl4(A)2] (where L = hmp, A = H2O; L = hmp, A = pyridine; L
= hmp, A = 4‐picoline; L = hep, A = H2O), and [Cr(hmp)(hmpH)Cl2. Magnetic studies show relatively
weak antiferromagnetic exchange interactions between the Cr(III) centres and DFT calculations are
used to develop magneto‐structural correlations, showing that the magnitude and sign of the J value
is strongly dependent upon the orientation of the dihedral angle formed between the bridging Cr2O2
plane and the O–R vector of the bridging group, and the Cr–O–Cr–O dihedral angle.
Chapter 3 builds on the work from the previous chapter with discussion of a large family of
chromium(III) dimers, synthesised using a combination of carboxylate and diethanolamine type
ligands. The compounds have the general formula [Cr2(R1‐deaH)2(O2CR2)Cl2]Cl where R1 = Me and R2 =
H, Me, CMe3, Ph, 3,5‐(Cl)2Ph, (Me)5Ph, R1 = Et and R2 = H, Ph. The compound [Cr2(Me‐deaH)2Cl4] was
also synthesised in order to study the effect of removing/adding the carboxylate bridge to the
observed magnetic behaviour. Magnetic studies reveal ferromagnetic exchange interactions between
the Cr(III) centres in the carboxylate bridged family with coupling constants in the range +0.37 < J <
+8.02 cm‐1. Removal of the carboxylate to produce the dialkoxide‐bridged compound results in
antiferromagnetic exchange between the Cr(III) ions. DFT calculations to further develop the magneto-structural
correlations reveal the ferromagnetic exchange is the result of an orbital counter-complementarity
effect occurring upon introduction of the bridging carboxylate.
Chapter 4 reports a family of heterometallic Anderson‐type ‘wheels’ of general formula
[MIII
2MII
5(hmp)12](ClO4)4 (where MIII = Cr or Al and MII = Ni or Zn giving [Cr2Ni5], [Cr2Zn5], [Al2Ni5] and
[Al2Zn5]; hmpH = 2‐pyridinemethanol) synthesised solvothermally. The metallic skeleton describes a
centred hexagon with the MIII sites disordered around the outer wheel. The structural disorder is
characterised via single crystal X‐ray crystallography, 1‐3D 1H and 13C solution‐state NMR spectroscopy
of the diamagnetic analogue, and solid‐state 27Al MAS NMR spectroscopy of the Al containing
analogues. Alongside ESI mass spectrometry, these techniques show that structure is retained in
solution, and that the disorder is present in both the solution and solid‐state. Solid‐state dc
susceptibility and magnetisation measurements on [Cr2Zn5] and [Al2Ni5] reveal the Cr‐Cr and Ni‐Ni
exchange interactions to be JCr‐Cr = ‐1 cm‐1 and JNi‐Ni,r = ‐5 cm‐1, JNi‐Ni,c = 10 cm‐1. Fixing these values
allows us to extract JCr‐Ni,r = ‐1.2 cm‐1, JCr‐Ni,c = 2.6 cm‐1, the exchange between adjacent Ni and Cr ions
on the ring is antiferromagnetic and between Cr ions on the ring and the central Ni ion is
ferromagnetic.
Chapter 5 focusses on planar molecules, espanding the family of heterometallic Anderson‐type
‘wheels’ discussed in chapter 4 to include MIII = Cr, Al and MII = Co, Fe, Mn, Cu, affording five new
species of formulae [Cr2Co5(hmp)12](ClO4)4, [Cr2Fe5(hmp)12](ClO4)4, [Cr2Mn5(hmp)12](ClO4)4,
[Cr2Cu5(hmp)12](ClO4)2(NO3)2 and [Al2Co5(hmp)12](ClO4)4. As per previous family members, the two MIII
sites are disordered around the outer wheel, with the exception of [Cr2Cu5] where the the CuII sites
are localised. A structurally related, but enlarged planar disc possessing a [MIII
6MII] hexagon capped
on each edge by a CuII ion is also reported, which is formed only when MIII = Al and MII = Cu. In
[AlIII
6CuII
7(OH)12(hmp)12](ClO4)6(NO3)2 the Anderson moiety contains a central, (symmetry‐imposed)
octahedral CuII ion surrounded by a wheel of AlIII ions. Solid‐state dc susceptibility and magnetisation
measurements reveal the presence of competing exchange interactions in the Anderson wheels
family, and weak antiferromagnetic exchange between the CuII ions in [Al6Cu7].
Chapter 6 describes two heterometallic wheels of formula [(VIVO)2MII
5(hmp)10Cl2](ClO4)2∙2MeOH
(where MII = Ni or Co) displaying the same Anderson‐type structure as seen in chapters 4 and 5,
however the use of the vanadyl moiety has the effect of removing the disorder, with the two vanadyl
ions sitting on opposing sides of the ring. The magnetic properties of both show competing antiferroand
ferromagnetic interactions
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