711 research outputs found
Structures and Vibrational Spectra of CH,OCH,CH,OH : The
Ab initio calculations at the MP2/6-31G* and MP2/6-31G*//6-31G* levels have been carried out for the monomer
of 2-methoxyethanol (CH,OCH,CH,OH). The MP2/6-31G* results indicate that the two more stable conformers
(tGgâ and gGgâ) display intramolecular hydrogen bonds directed from the hydroxy H atom to one of the lone pairs
of the ether 0 atom, and that the tGgâ conformer is 6.3 kJ mol-â more stable than the gGgâ conformer. As the
MP2/6-31G* and MP2/6-3lG*//6-31G* calculations do not yield results differing by more than a few tenths of a kJ
mol-â, it is concluded that the structure-sensitive and the dynamic correlation corrections are far from being
additive. While the optimization of geometry for the correlated wavefunction generally leads to increase of bond
lengths and reduction of bond angles, on the whole the geometrical parameters undergo similar changes in
different conformers. Ab initio harmonic 6-31G* derived force fields were used to perform normal mode
analyses for the more stable conformers. The calculated v(CH) frequencies are found to correlate linearly with
some of the ab initio calculated CH bond lengths. An interpretation of the FTIR and Raman spectra for the liquid
phase consonant with the structural and vibrational ab initio results is presented. Two spectral features
observed both in Raman and in FTIR spectra and associated with v(0H) in monomeric species are ascribed to
conformers, in accord with the theoretical and experimental results. On the whole, both the structural and the
vibrational results presented point to a distinction between the hydrogen-bonded G-type conformers (tGgâ and
gGgâ) and the higher energy T-type conformers (tTg and tTt)
Hydrogen-Bonded Dimers of CH3OCH2CH2OH: Ab Initio Structures and Multivariate Analysis
Structures and vibrational frequencies of relevant hydrogen-bonded dimers of 2-methoxyethanol are obtained
at the 3-21G*//Ah41 level (the 3-21G* basis set included polarization functions deliberately added to second
period atoms) and the results analyzed by standard multivariate methods. Dimers built from the same pair
of isolated monomers belong to the same homologous series. The most stable dimer is obtained from the
most stable conformations of both monomers, has a 10-membered intermolecular ring with a boat-chairboat
conformation, and presents a zero dipole moment. In addition, the most stable dimers of the three
homologous series have 10-membered rings with relatively symmetric conformations and zero or very low
dipole moments. The energies of the monomers in these dimers-monomers with geometries frozen in the
dimer-are close to the isolated and relaxed monomers energies. Generally speaking, OH 0 and CH 0
hydrogen bonds are found to contribute appreciably for the stability of the dimers. In particular, for the
second most stable dimer, two of the three CH -0 hydrogen bonds are shorter than the intramolecular OH- 0
bond for the isolated monomer. Multivariate analysis of all the results shows that the 0. *H-0 angle is
highly correlated with the H-0 bond length and that the COC and OCC angles are also highly correlated for
both monomers, hence confirming that each monomer in a dimer keeps essentially the same conformation it
has in the isolated monomer. The first and second principal components include all the highly correlated
variables and account for 45% of the total variance. 3-D plots of the three most important principal components
confirm a strong structural resemblance both for 10-membered ring dimers of homomeric series, Le., formed
by the same monomers, and for the more stable dimers in each homologous series. In addition, among the heteromeric dimers with seven membered rings, the ones whose first conformation is G or Gâ are less stable and located in a separate group
Weld lines in extrusion: Understanding the role of the flow conditions
This work reports the implemen
tation and verification of a new so
lver in OpenFOAMÂŽ open source
computational library, able to cope w
ith integral viscoelastic
models based on the integral upper-convected Maxwell
model. The code is verified through the
comparison of its predictions with anal
ytical solutions and numerical results
obtained with the differential
upper-convected Maxwell modelCAPES, FCT projects PEsT-C/CTM/LA0025/2013, PTDC/MAT/121185/2010 and FEDE
Influence of the microstructure on the creep behaviour of Tin-Silver-Copper solder
A common failure mode of electronic printed circuit boards (PCBâs) is the appearance of cold solder joints between the component and PCB, during product life. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. With todayâs solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. As fatigue life decreases with increasing plastic strain, creep occurrence should have significant impact, especially during thermal cycles and, thus, should be studied. Through the cooling phase, on the production of PCB assemblyâs by the reflow technology, the hoven atmosphere temperature is adjusted in order to control the cooling rate. Narrow criteria is used so as to control the inter-metallic compounds (IMC) thickness, PCB assembly distortion and defects due to thermal shock. The cooling rate also affects solder microstructure, which has direct impact on creep behaviour and, thus, on the soldered joint reliability.
In this paper, a dynamic mechanical analyser (DMA) is used to study the influence of the solder cooling rate on its creep behaviour. SAC405 samples with two distinct cooling rates were produced: inside a hoven cooling and by water quenching. Creep tests were made on three-point-bending clamp configuration, isothermally at 25 °C, 50 °C and 75 °C and under three separate levels of stress, 3, 5 and 9 MPa. The results show that creep behaviour has a noticeable cooling rate dependence. It was also noticed that creep propensity is exacerbated by the temperature at which stresses are applied, especially for the slower cooling rates. Creep mechanisms were related to the solder microstructural constituents, namely by the amount of phases ant their morphology.The authors would like to express his acknowledgments for the
support given by the Portugal Incentive System for Research and
Technological Development. Project in co-promotion
This research is sponsored by the Portugal Incentive System for
Research and Technological Development.
This work is supported by: European Structural and Investment
Funds in the FEDER component, through the Operational
Competitiveness and Internationalization Programme
(COMPETE 2020) [Project nÂş 002814; Funding Reference:
POCI-01-0247-FEDER-002814]. This work was financed by
FCT, under the Strategic Project UID/SEM/04077/2013;
PEst2015-2020 with the reference UID/CEC/00319/2013 and
UID/FIS/04650/2013
Filtração em cerâmica microporosa aplicada à remoção de cor e turbidez de ågua para abastecimento público
Um filtro cerâmico com porosidade de 0,1Îźm, 60 cm de altura e 6 cm de diâmetro e 1 cm de espessura foi utilizado para estudar a remoção de cor e turbidez da ĂĄgua bruta. A unidade apresentava 0,113m² de superfĂcie externa e estava montada no interior de uma coluna em acrĂlico com 100 cm de altura e 23 cm de diâmetro, com volume Ăştil de 41,5 L. A ĂĄgua bruta, utilizada na pesquisa, foi proveniente de uma represa onde os valores de turbidez variaram de 2,3 a 2,8 NTU e cor aparente de 93 e 109 PtCo. Foram empregadas 3 diferentes taxas de aplicação, sendo de 1,82, 3,16 e 4,49m3/m2.dia, onde foram realizadas trĂŞs carreiras de filtração para cada taxa. A duração de cada carreira de filtração estabilizou em 100, 42 e 26 minutos, respectivamente para cada taxa de aplicação. As amostras de ĂĄgua, utilizadas para verificar sua qualidade, foram coletadas, na entrada e saĂda do filtro a cada 5 cm de perda de carga atĂŠ completar 20 cm. Os resultados obtidos demonstraram uma eficiĂŞncia na remoção de turbidez entre 75 e 80%, resultando valores de entre 0,53 e 0,58 NTU para a Ăşltima carreira de filtração para cada taxa de aplicação. Em contrapartida o sistema nĂŁo se mostrou eficiente para remoção de cor aparente ficando entre 27 e 38%, mantendo valores elevados, ou seja, superiores a 62 PtCo, dessa forma o sistema nĂŁo se mostrou eficiente para a remoção de cor
Multicentric Genome-Wide Association Study for Primary Spontaneous Pneumothorax
Despite elevated incidence and recurrence rates for Primary Spontaneous Pneumothorax (PSP), little is known about its etiology, and the genetics of idiopathic PSP remains unexplored. To identify genetic variants contributing to sporadic PSP risk, we conducted the first PSP genome-wide association study. Two replicate pools of 92 Portuguese PSP cases and of 129 age- and sex-matched controls were allelotyped in triplicate on the Affymetrix Human SNP Array 6.0 arrays. Markers passing quality control were ranked by relative allele score difference between cases and controls (|RASdiff|), by a novel cluster method and by a combined Z-test. 101 single nucleotide polymorphisms (SNPs) were selected using these three approaches for technical validation by individual genotyping in the discovery dataset. 87 out of 94 successfully tested SNPs were nominally associated in the discovery dataset. Replication of the 87 technically validated SNPs was then carried out in an independent replication dataset of 100 Portuguese cases and 425 controls. The intergenic rs4733649 SNP in chromosome 8 (between LINC00824 and LINC00977) was associated with PSP in the discovery (P = 4.07E-03, ORC[95% CI] = 1.88[1.22-2.89]), replication (P = 1.50E-02, ORC[95% CI] = 1.50[1.08-2.09]) and combined datasets (P = 8.61E-05, ORC[95% CI] = 1.65[1.29-2.13]). This study identified for the first time one genetic risk factor for sporadic PSP, but future studies are warranted to further confirm this finding in other populations and uncover its functional role in PSP pathogenesis
Effects of previous carbohydrate supplementation on muscular fatigue: double-blind, randomized, placebo-controlled crossover study
Abstract AIMS The aim of this study was to examine the effects of previous carbohydrate supplementation on high-volume resistance exercise performance METHODS Twenty males physically independent adults aged âĽ18 years participated in a double-blind randomized placebo-controlled crossover study. Sixty minutes before the experimental protocol, each participant ingested 0,6 g.kg of body mass-1 of carbohydrate supplementation or placebo. Maximum voluntary isometric contraction tests were performed before and after the dynamic fatigue induction protocol consisting of 10 sets of 8 repetitions of right leg knee extensors at 120Âş s-1. RESULTS Lower decrement of the isometric peak torque (p<0,001) and of the rate of torque development (p<0,001) was observed in carbohydrate supplementation after the dynamic protocol. Both concentric and eccentric peak torque differed significantly (p<0,001) between carbohydrate supplementation and placebo treatments from the second set, although the slope of the force-repetitions curve was not different between them. Additionally, the carbohydrate supplementation resulted in a lower session rating of perceived exertion (p<0,05). CONCLUSIONS Previous carbohydrate supplementation attenuates muscle fatigue and internal load exercise in a high-volume isokinetic leg protocol
listening to what matters for the patients and health professionals
Funding Information: The authors would like to acknowledge the members of the medical and patient committees for the input, advice and experiences shared for the guidance of this study. Namely, to AM, SP, JP, LR, MC, RF, TR and JB for being part of the patient committee and to JJ, EM, LB, DCo, DCa, CTL, RA, CL and AE for integrating the medical committee. We also want to acknowledge the volunteers from the NOVA Sci & Tech Volunteer program that helped with the organisation of this project. Funding Information: This work was supported by the CDG & AlliesâProfessionals and Patient Associations International Network (CDG&Allies-PPAIN) and by national funds from FCTâFundação para a CiĂŞncia e a Tecnologia, I.P., in the scope of the Project UIDP/04378/2020 and UIDB/04378/2020 of the Research Unit on Applied Molecular BiosciencesâUCIBIO, the Project LA/P/0140/2020 of the Associate Laboratory Institute for Health and Bioeconomyâi4HB C.P. and R.F. were funded by Fundação para a CiĂŞncia e Tecnologia with the Grants SFRH/BD/138647/2018 and (SFRH/BD/124326/2016) respectively. Publisher Copyright: Š 2022, The Author(s).Background: Congenital disorders of glycosylation (CDG) are a growing group of rare genetic disorders. The most common CDG is phosphomannomutase 2 (PMM2)-CDG which often has a severe clinical presentation and life-limiting consequences. There are no approved therapies for this condition. Also, there are no validated disease-specific quality of life (QoL) scales to assess the heterogeneous clinical burden of PMM2-CDG which presents a challenge for the assessment of the disease severity and the impact of a certain treatment on the course of the disease. Aim and methods: This study aimed to identify the most impactful clinical signs and symptoms of PMM2-CDG, and specific patient and observer reported outcome measures (PROMs and ObsROMs, respectively) that can adequately measure such impact on patientsâ QoL. The most burdensome signs and symptoms were identified through input from the CDG community using a survey targeting PMM2-CDG families and experts, followed by family interviews to understand the real burden of these symptoms in daily life. The list of signs and symptoms was then verified and refined by patient representatives and medical experts in the field. Finally, a literature search for PROMs and ObsROMs used in other rare or common diseases with similar signs and symptoms to those of PMM2-CDG was performed. Results: Twenty-four signs/symptoms were identified as the most impactful throughout PMM2-CDG patientsâ lifetime. We found 239 articles that included tools to measure those community-selected PMM2-CDG symptoms. Among them, we identified 80 QoL scales that address those signs and symptoms and, subsequently, their psychometric quality was analysed. These scales could be applied directly to the PMM2-CDG population or adapted to create the first PMM2-CDG-specific QoL questionnaire. Conclusion: Identifying the impactful clinical manifestations of PMM2-CDG, along with the collection of PROMs/ObsROMs assessing QoL using a creative and community-centric methodology are the first step towards the development of a new, tailored, and specific PMM2-CDG QoL questionnaire. These findings can be used to fill a gap in PMM2-CDG clinical development. Importantly, this methodology is transferable to other CDG and rare diseases with multiple signs and symptoms.publishersversionpublishe
Selection of Saccharomyces cerevisiae strains for efficient very high gravity bio-ethanol fermentation processes
An optimized very high gravity (VHG)
glucose medium supplemented with low cost nutrient
sources was used to evaluate bio-ethanol production
by 11 Saccharomyces cerevisiae strains. The industrial
strains PE-2 and CA1185 exhibited the best
overall fermentation performance, producing an ethanol
titre of 19.2% (v/v) corresponding to a batch
productivity of 2.5 g l-1 h-1, while the best laboratory
strain (CEN.PK 113-7D) produced 17.5% (v/v)
ethanol with a productivity of 1.7 g l-1 h-1. The
results presented here emphasize the biodiversity
found within S. cerevisiae species and that naturally
adapted strains, such as PE-2 and CA1185, are likely
to play a key role in facilitating the transition from
laboratory technological breakthroughs to industrialscale
bio-ethanol fermentations.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/BIO/66151/2006, SFRH/
BD/64776/2009, SFRH/BPD/44328/
200
Standalone vertex ďŹnding in the ATLAS muon spectrometer
A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at âs = 7 TeV collected with the ATLAS detector at the LHC during 2011
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