952 research outputs found
Synthesis of highly substituted alkenes by sulfur-mediated olefination of N-tosylhydrazones
Tetraphenylethylenes (TPEs) are well-known for their aggregation-induced emission properties. The synthesis of TPE derivatives, as well as other highly substituted olefins, generally requires the use of hazardous reagents, such as metalorganic compounds, to overcome the high activation energies caused by the sterically congested double bond. Herein, we present an efficient and metal-free procedure for the synthesis of tetraarylethylenes via alkylidene-homocoupling of N-tosylhydrazones, derived from readily available benzophenones, in excellent yields. The method relies only on cheap and benign additives, i.e. elemental sulfur and potassium carbonate, and easily competes with other established procedures in terms of scope, yield and practicability. A mechanistic study revealed a diazo compound, a thioketone and a thiirane as key intermediates in the pathway of the reaction. Based on this, a modified method, which allows for selective alkylidene-cross-coupling, generating a broader scope of tri- and tetrasubstituted olefins in good yields, is showcased as well
Novel Access to Known and Unknown Thiourea Catalyst via a Multicomponent-Reaction Approach
Thioureas are frequently used in organocatalysis and typically rely on 3,5âbis(trifluoromethyl) phenyl moieties motifs to enhance their catalytic activity. In this work, these common motifs were replaced with tailorable functional groups, such as ester or sulfone aryls, applying elemental sulfur in a multicomponent reaction (MCR) strategy for the first time for thiourea catalyst synthesis. First, several thioureas bearing aryl, benzylic or aliphatic moieties were synthesized and tested for their hydrogen bonding strength by evaluating thiourea phosphine oxide complexes via P NMR and their catalytic activity in an Ugi fourâcomponent reaction (Uâ4CR). Finally, ester and sulfone aryl thioureas were tested in the aminolysis of propylene carbonate, leading to conversions similar to those previously reported in the literature using the 3,5âbis(trifluoromethyl)phenyl moiety, proving that these groups are suitable alternatives for the trifluoromethyl group
Removal of Transition-Metal Ions by Metal-Complexing Polythiosemicarbazone Membranes
Membrane technology is one of the many strategies to remove transition-metal ions from aqueous streams because of its relatively lower costs and ease of operation. Typically, adsorbent materials are added into polymeric membranes to impart chelating/complexing properties, but this often results in a limited number of adsorption sites within the membrane. In this work, polythiosemicarbazone (pTSC) is proposed as a material to prepare polymeric membranes due to its metal-complexing ligands in the backbone, providing more adsorption sites. The polymer was easily processed into membranes via the nonsolvent-induced phase separation technique and exhibited asymmetric structures with adequate mechanical strength. The porosity of the membranes was controlled by increasing the polymer concentration in the casting solution, leading to ultrafiltration- and nanofiltration-type membranes with permeabilities ranging from 30 to 0.7 L·m·h·bar. The resulting pTSC membranes were applied for the removal of silver and copper ions in batch and, in the case of silver ions, also in dynamic adsorption experiments. The maximum removal rate of 17 mg·g for silver and 3.8 mg·g for copper ions was obtained in the batch removal experiment. Streaming potential, pH measurements, and infrared spectroscopy (FTIR) were conducted to verify the anionic binding of TSC groups, while neutral binding modes were revealed by FTIR and batch removal experiments. Furthermore, the removal of silver ions was also successfully demonstrated in a flow setup operated at 4 bar of applied pressure. The streaming potential and energy-dispersive X-ray (EDX) spectroscopy conducted on the membranes after the flow tests confirmed the complexation by TSC-functional groups as the separation mechanism. Finally, partial desorption of the silver ions was successfully conducted in water to demonstrate the reusability of pTSC membranes
Dual sequence definition increases the data storage capacity of sequence-defined macromolecules
Sequence-defined macromolecules offer applications in the field of data storage. Challenges include synthesising precise and pure sequences, reading stored information and increasing data storage capacity. Herein, the synthesis of dual sequence-defined oligomers and their application for data storage is demonstrated. While applying the well-established Passerini three-component reaction, the degree of definition of the prepared monodisperse macromolecules is improved compared to previous reports by utilising nine specifically designed isocyanide monomers to introduce backbone definition. The monomers are combined with various aldehyde components to synthesise dual-sequence defined oligomers. Thus, the side chains and the backbones of these macromolecules can be varied independently, exhibiting increased molecular diversity and hence data storage capacity per repeat unit. In case of a dual sequence-defined pentamer, 33 bits are achieved in a single molecule. The oligomers are obtained in multigram scale and excellent purity. Sequential read-out by tandem ESI-MS/MS verifies the high data storage capacity of the prepared oligomers per repeat unit in comparison to other sequence defined macromolecules
NestemÀisten jÀtteiden vastaanotto ja kÀsittely TarastenjÀrven jÀtekeskuksessa : Selvitys vaihtoehtoisista menetelmistÀ
NestemÀiset jÀtteet ovat erilaisia loka-autoilla kuljetettavia jÀtteitÀ, jotka koostuvat nesteestÀ ja kiintoaineksesta. TÀllaisia jÀtteitÀ ovat esimerkiksi hiekan- ja rasvanerotuskaivoista imetyt nesteet sekÀ teollisuudessa syntyvÀt jÀtevesilietteet. NestemÀisiÀ jÀtteitÀ ei ole Valtioneuvoston pÀÀtöksestÀ enÀÀ vuoden 2002 jÀlkeen saanut sijoittaa sellaisenaan kaatopaikkapenkkaan, vaan ne on tullut esikÀsitellÀ nesteen poistamiseksi. TÀhÀn asti nestemÀiset jÀtteet on kÀsitelty TarastenjÀrven jÀtekeskuksessa painovoimaisesti erottelemalla. MenetelmÀ on ollut toimiva, mutta on pÀivityksen tarpeessa. TÀmÀn opinnÀytetyön tarkoituksena olikin tutkia erilaisia vaihtoehtoja nestemÀisten jÀtteiden vastaanotolle sekÀ kÀsittelylle TarastenjÀrven jÀtekeskuksessa, sekÀ arvioida eri vaihtoehtojen kustannuksia mikÀli mahdollista. Myös tarvetta haitta-aineiden, kuten metallien ja öljyjen poistamiselle tutkittiin. Työn laatimisessa hyödynnettiin olemassa olevaa tieteellistÀ kirjallisuutta sekÀ asiantuntijahaastatteluja. Työn tilaajana toimi Pirkanmaan JÀtehuolto Oy.
Selvitystyön tuloksena kĂ€vi ilmi, ettĂ€ yleisimmĂ€t menetelmĂ€t nesteiden ja kiinteiden ainesten erottamiseen ovat painovoimainen erottelu ja suodatus. Painovoimaiset erottelijat ovat useimmiten kiinteĂ€seinĂ€isiĂ€ altaita, joissa kiintoaines laskeutuu painovoimaisesti altaan pohjalle ja pinnalle jÀÀnyt kirkastunut neste ohjataan ylivuotona jatkokĂ€sittelyyn. Kiintoaineksen ollessa kevyempÀÀ kuin vesi, se erottuu nesteen pinnalle. Suodattimien toiminta taas perustuu puolilĂ€pĂ€isevÀÀn suodatusmediaan, joka pÀÀstÀÀ nesteen lĂ€pi, mutta jĂ€ttÀÀ kiintoaineksen suodattimeen. Suodattimet voivat olla esimerkiksi paineistettuja tai painovoimalla toimivia. Geotuubit ovat erÀÀnlaisia paineistettuja sĂ€kkisuodattimia, joita on kĂ€ytössĂ€ myös jĂ€tekeskuksissa. Useissa kĂ€sittelymenetelmissĂ€ kĂ€ytetÀÀn apuna myös saostuskemikaaleja, jotka edistĂ€vĂ€t kiintoaineksen erottumista nesteestĂ€. Haitta-aineiden osalta helpoin ratkaisu on poistaa ne kiintoaineksen mukana ja kĂ€sitellĂ€ ne pilaantuneiden maiden kanssa jĂ€tekeskuksessa. MikĂ€li haitta-aineet ovat nesteessĂ€ liukoisessa muodossa, voidaan apuna kĂ€yttÀÀ saostuskemikaaleja, kuten alumiini- tai rautasuoloja. Ăljyjen erottamisessa olisi mahdollista hyödyntÀÀ öljynerotuskaivoa.
Kirjallisuuden sekÀ haastattelujen perusteella pÀivitetty versio painovoimaisesta erottelujÀrjestelmÀstÀ sekÀ geotuubimenetelmÀ vaikuttavat parhailta kÀytettÀvissÀ olevilta ratkaisuilta. Suurin haaste jÀtekeskuksen nestemÀisten jÀtteiden kÀsittelyssÀ on kuitenkin se, ettÀ nesteiden ominaisuudet eroavat kuormittain hyvin paljon toisistaan. TÀhÀn voitaisiin vaikuttaa jÀtteiden tarkemmalla lajittelulla vastaanottovaiheessa. KÀsittelymenetelmÀÀ valittaessa tulee kuitenkin pohtia jÀrjestelmÀn kuluja sekÀ hyötyjÀ pitkÀllÀ aikavÀlillÀ niin, ettÀ pÀÀstÀÀn parhaaseen mahdolliseen puhdistuslopputulokseen.Liquid wastes are solid-liquid mixtures such as wastes from sand and grease separation wells and industrial wastewaters. Since 2002 liquid wastes have no longer been allowed to be placed at a waste disposal site according to the decree 1049/1999 of the Finnish Council of State. Therefore liquid wastes have to be dewatered before final disposal. At the moment liquid wastes are treated at the TarastenjÀrvi waste management centre with gravitational separation but the system needs updating.
The aim of this study was to provide Pirkanmaan JĂ€tehuolto Oy with different methods of liquid waste handling as well as evaluate the costs of a new system if possible. Also the need for contaminant removal was taken into consideration. The study was carried out by literature reviews and interviewing professionals of the industry.
The results showed that the most common methods of solid-liquid separation are gravitational separation and filtration. Gravitational separators are usually containers in which the solid matter is allowed to separate either by sedimentation or flotation. Filters have a semi-permeable filter media which traps the solid matter but allows the liquid to flow through. Geotubes are an example of filters that are currently being used in several waste management centres. Many separation methods also require the use of polymers or flocculants to operate effectively. When contaminants are in a settleable form they are rather easy to be removed and treated with the solid matter. If the contaminants are dissolved in the liquid it might be possible to make them settle by adding aluminium or iron sulphate. Also an oil separation well could be used to separate oils from the liquid phase.
Based on the literature reviews and interviews an upgraded gravitational system or the geotube method seem to be the best options. However, more tests should be conducted to see if these methods would work in practice. The biggest challenge is that the incoming liquid waste loads at TarastenjÀrvi are not homogenous which makes it difficult to choose a solution that works well for all of them. The situation could be improved with more precise classification of the waste loads and handling them separately according to their characteristics. The most important aspect is to find a long-term cost-effective solution that can provide sufficient handling of the liquid wastes
The Casimir energy of skyrmions in the 2+1-dimensional O(3)-model
One-loop quantum corrections to the classical vortices in 2+1 dimensional
O(3)-models are evaluated. Skyrme and Zeeman potential terms are used to
stabilize the size of topological solitons. Contributions from zero modes,
bound-states and scattering phase-shifts are calculated for vortices with
winding index n=1 and n=2. For both cases the S-matrix shows a pronounced
series of resonances for magnon-vortex scattering in analogy to the
well-established baryon resonances in hadron physics, while vortices with n>2
are already classically unstable against decay. The quantum corrections
destabilize the classically bound n=2 configuration. Approximate independence
of the results with respect to changes in the renormalization scale is
demonstrated.Comment: 24 pages LaTeX, 14 figure
Low Efficiency of Homology-Facilitated Illegitimate Recombination during Conjugation in Escherichia coli
Homology-facilitated illegitimate recombination has been described in three naturally competent bacterial species. It permits integration of small linear DNA molecules into the chromosome by homologous recombination at one end of the linear DNA substrate, and illegitimate recombination at the other end. We report that homology-facilitated illegitimate recombination also occurs in Escherichia coli during conjugation with small non-replicative plasmids, but at a low frequency of 3Ă10â10 per recipient cell. The fate of linear DNA in E. coli is either RecBCD-dependent degradation, or circularisation by ligation, and integration into the chromosome by single crossing-over. We also report that the observed single crossing-overs are recA-dependent, but essentially recBCD, and recFOR independent. This suggests that other, still unknown, proteins may act as mediator for the loading of RecA on DNA during single crossing-over recombination in E. coli
Persistent anthrax as a major driver of wildlife mortality in a tropical rainforest
Anthrax is a globally important animal disease and zoonosis. Despite this, our current knowledge of anthrax ecology is largely limited to arid ecosystems, where outbreaks are most commonly reported. Here we show that the dynamics of an anthrax-causing agent, Bacillus cereus biovar anthracis, in a tropical rainforest have severe consequences for local wildlife communities. Using data and samples collected over three decades, we show that rainforest anthrax is a persistent and widespread cause of death for a broad range of mammalian hosts. We predict that this pathogen will accelerate the decline and possibly result in the extirpation of local chimpanzee (Pan troglodytes verus) populations. We present the epidemiology of a cryptic pathogen and show that its presence has important implications for conservation
Quantum state preparation and macroscopic entanglement in gravitational-wave detectors
Long-baseline laser-interferometer gravitational-wave detectors are operating
at a factor of 10 (in amplitude) above the standard quantum limit (SQL) within
a broad frequency band. Such a low classical noise budget has already allowed
the creation of a controlled 2.7 kg macroscopic oscillator with an effective
eigenfrequency of 150 Hz and an occupation number of 200. This result, along
with the prospect for further improvements, heralds the new possibility of
experimentally probing macroscopic quantum mechanics (MQM) - quantum mechanical
behavior of objects in the realm of everyday experience - using
gravitational-wave detectors. In this paper, we provide the mathematical
foundation for the first step of a MQM experiment: the preparation of a
macroscopic test mass into a nearly minimum-Heisenberg-limited Gaussian quantum
state, which is possible if the interferometer's classical noise beats the SQL
in a broad frequency band. Our formalism, based on Wiener filtering, allows a
straightforward conversion from the classical noise budget of a laser
interferometer, in terms of noise spectra, into the strategy for quantum state
preparation, and the quality of the prepared state. Using this formalism, we
consider how Gaussian entanglement can be built among two macroscopic test
masses, and the performance of the planned Advanced LIGO interferometers in
quantum-state preparation
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
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