37 research outputs found
Pursuing colloidal diamond
The endeavor to selectively fabricate cubic diamond is challenging due to the
formation of competing phases such as its hexagonal polymorph or others
possessing similar free energy. The necessity to achieve that is of paramount
importance, since the cubic diamond is the only polymorph exhibiting a complete
photonic bandgap making it a promising candidate in view of photonic
applications. Herein, we demonstrate that due to the presence of external field
and delicate manipulation of its strength we can attain the selectivity in the
formation of cubic diamond in a one-component system comprised of designer
tetrahedral patchy particles. The driving force of such phenomena is the
structure of the first adlayer which is commensurate with (110) face of the
cubic diamond. Moreover, after a successful nucleation event, once the external
field is turned off, the structure remains stable, paving an avenue for a
further post-synthetic treatment
Effect of 2-(4-fluorophenylamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole on the molecular organisation and structural properties of the DPPC lipid multibilayers
AbstractInteractions and complex formation between lipids and biologically active compounds are crucial for better understanding of molecular mechanisms occurring in living cells. In this paper a molecular organisation and complex formation of 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT) in DPPC multibilayers are reported. The simplified pseudo binary phase diagram of this system was created based on the X-ray diffraction study and fourier transform infrared spectroscopic data. The detailed analysis of the refraction effect indicates a much higher concentration of FABT in the polar zones during phase transition. Both the lipid and the complex ripple after cooling. It was found that FABT occupied not only the hydrophilic zones of the lipid membranes but also partly occupied the central part of the non polar zone. The infrared spectroscopy study reveals that FABT strongly interact with hydrophilic (especially PO2â) and hydrophobic (especially âkinkâ vibrations of CH2 group). The interactions of FABT molecules with these groups are responsible for changes of lipid multibilayers observed in X-ray diffraction study
Juvenile tench ( Tinca tinca L.) response to practical diets with different replacement levels of fish meal by pea protein concentrate supplemented with methionine
.The effects of methionine supplementation in diets with different replacement levels of fish meal (FM) by pea protein concentrate (PPC) on survival, growth performance and body composition of juvenile tench (0.39 g of initial weight) were studied in a 90-day experiment. Six practical diets (50% crude protein) differing in replacement level of FM by PPC were tested: 0% (control diet), 35%,45%, 60%, 75% or 85%, corresponding to 0, 285, 366, 487, 608 and 685.4 g PPC kgâ1 diet respectively. To provide the same amount as in control diet, methionine was included from the 45% substitution level. Survival rates were high, between 93.7% and 100%, without differences among treatments. Juveniles fed 75% and 85% of replacement diets showed lower (p < 0.05) weight and specific growth rate, which cannot be attributed to methionine deficiency. In all treatments, percentages of fish with externally visible deformities were low (under 0.1%). The increase in PPC diet content resulted in a significant reduction of lipid content in whole-body juvenile. Minimum methionine requirements for juvenile tench could be estimated in 10 g kgâ1 diet and supplementation over this amount would be not necessary. Juvenile tench exhibited a high tolerance to PPC dietary content, up to 487 g kgâ1, without affecting growth performance, which make possible to consider this vegetal source of protein as a suitable substitute to FM.S
Shortest Reconfiguration of Matchings
Imagine that unlabelled tokens are placed on the edges of a graph, such that
no two tokens are placed on incident edges. A token can jump to another edge if
the edges having tokens remain independent. We study the problem of determining
the distance between two token configurations (resp., the corresponding
matchings), which is given by the length of a shortest transformation. We give
a polynomial-time algorithm for the case that at least one of the two
configurations is not inclusion-wise maximal and show that otherwise, the
problem admits no polynomial-time sublogarithmic-factor approximation unless P
= NP. Furthermore, we show that the distance of two configurations in bipartite
graphs is fixed-parameter tractable parameterized by the size of the
symmetric difference of the source and target configurations, and obtain a
-factor approximation algorithm for every if
additionally the configurations correspond to maximum matchings. Our two main
technical tools are the Edmonds-Gallai decomposition and a close relation to
the Directed Steiner Tree problem. Using the former, we also characterize those
graphs whose corresponding configuration graphs are connected. Finally, we show
that deciding if the distance between two configurations is equal to a given
number is complete for the class , and deciding if the diameter of
the graph of configurations is equal to is -hard.Comment: 31 pages, 3 figure
Spectroscopic Studies of Intramolecular Proton Transfer in 2-(4-Fluorophenylamino)-5-(2,4-Dihydroxybenzeno)-1,3,4-Thiadiazole
Spectroscopic studies of the biologically active compound 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT), have been performed. Absorption studies in the UV-Vis region for FABT in polar solvents, like water or ethanol, exhibit the domination of the enol form over its keto counterpart, with a broad absorption band centered around 340Â nm. In non-polar solvents such as n-heptane or heavier alkanes the 340Â nm absorption band disappears and an increase of the band related to the keto form (approximately 270Â nm) is observed. Fluorescence spectra (with 270Â nm and 340Â nm excitation energies used) show a similar dependence: for FABT in 2-propanol a peak at about 400Â nm dominates over that at 330Â nm while in n-heptane this relation is reversed. The solvent dependent equilibrium between the keto and enol forms is further confirmed by FTIR and Raman spectroscopies. As can be expected, this equilibrium also shows some temperature dependences. We note that the changes between the two tautomeric forms of FABT are not related to the permanent dipole moment of the solvent but rather to its dipole polarizability
Apophis planetary defense campaign
We describe results of a planetary defense exercise conducted during the close approach to Earth by the near-Earth asteroid (99942) Apophis during 2020 Decemberâ2021 March. The planetary defense community has been conducting observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. These community-led global exercises were carried out with the support of NASA's Planetary Defense Coordination Office and the International Asteroid Warning Network. The Apophis campaign is the third in our series of planetary defense exercises. The goal of this campaign was to recover, track, and characterize Apophis as a potential impactor to exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication. Based on the campaign results, we present lessons learned about our ability to observe and model a potential impactor. Data products derived from astrometric observations were available for inclusion in our risk assessment model almost immediately, allowing real-time updates to the impact probability calculation and possible impact locations. An early NEOWISE diameter measurement provided a significant improvement in the uncertainty on the range of hypothetical impact outcomes. The availability of different characterization methods such as photometry, spectroscopy, and radar provided robustness to our ability to assess the potential impact risk
Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences
The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & NemĂ©sio 2007; Donegan 2008, 2009; NemĂ©sio 2009aâb; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported
by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on
18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based
researchers who signed it in the short time span from 20 September to 6 October 2016
Structure and Physical Properties of Cardamonin: A Spectroscopic and Computational Approach
This is the first study of the crystal structure of cardamonin (CA) confirmed using single-crystal XRD analysis. In the crystal lattice of CA, two symmetry independent molecules are linked by hydrogen bonds within the layers and by the π···π stacking interactions in the columns which lead to the occurrence of two types of conformations among the CA molecules in the crystal structure. To better understand the stability of these arrangements in both crystals and the gaseous phase, seven different CA dimers were theoretically calculated. The molecular structures were optimized using density functional theory (DFT) at the B3LYP/6–311G+(d,p) level and the spectroscopic results were compared. It was found that the calculated configurations of dimer I and III were almost identical to the ones found in the CA crystal lattice. The calculated UV-Vis spectra for the CA monomer and dimer I were perfectly consistent with the experimental spectroscopic data. Furthermore, enhanced emissions induced by aggregated CA molecules were registered in the aqueous solution with the increase of water fractions. The obtained results will help to further understand the relation between a variety of conformations and the biological properties of CA, and the results are also promising in terms of the applicability of CA as a bioimaging probe to monitor biological processes
Coumarin Derivatives: The Influence of Cycloalkyl Groups at the C-3 Position on Intermolecular InteractionsâSynthesis, Structure and Spectroscopy
In this study, we explore the synthesis and solid-state characterization of four coumarin-3-carboxylic acid esters, each modified at the C-3 position with different cycloalkyl groups: cyclohexyl, menthyl, and iso-pulegyl. We conducted a detailed analysis of these compounds utilizing a variety of techniques such as a single-crystal X-ray diffraction, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy. Additionally, we calculated the dipole moments for these molecules. Our findings include a thorough structural assessment, highlighting the role of noncovalent interactions through Full Interaction Maps and Hirshfeld surface analysis. This study reveals the critical influence of the weak C-HâŠO hydrogen bonds in determining the solid-state architecture of these esters, whereas Ï-Ï stacking interactions appear to be negligible among the studied derivatives
Kolumnowa chromatografia cieczowa w rozdzielaniu i analizie peptydĂłw i biaĆek
Szybka ekspansja zastosowa peptydĂłw i biaĆek w biochemii i w medycynie, stymuluje ogromny wzrost zainteresowania metodami rozdzielania peptydĂłw. Elektroforeza ĆŒelowa i kapilarna to najczÄciej dotychczas wykorzystywane metody rozdzielania peptydĂłw i biaĆek, w celach identyfikacyjnych i analitycznych. Metody te nie sÄ
jednak przydatne do otrzymywania uĆŒytkowych iloĆci tych substancji. Obecnie HPLC jest najistotniejszÄ
metodÄ
oczyszczania i otrzymywania peptydĂłw i biaĆek. Ponadto techniki HPLC znajdujÄ
coraz wiÄksze zastosowanie w rozwijajÄ
cej siÄ proteomice. W pracy dokonano przeglÄ
du najwaĆŒniejszych technik chromatografii cieczowej, metod oraz procedur stosowanych do rozdzielania peptydĂłw i biaĆek jak rĂłwnieĆŒ obecnych trendĂłw w tym obszarze