Cation

We demonstrate experimentally and theoretically a nanofluidic device for the selective recognition of cesium ion by exploiting host-guest interactions inside confined geometry. For this purpose, a host molecule, i.e., the amine-terminated p-tert-butylcalix[4]arene-crown (t-BuC[4]C-NH2), is successfully synthesized and functionalized on the surface of a single conical nanopore fabricated in polyethylene terephthalate (PET) membrane through carbodiimide coupling chemistry. On exposure to cesium cation, the t-BuC[4]C-Cs+ complex is formed through host-guest interaction, leading to the generation of positive fixed charges on the pore surface. The asymmetrical distribution of these groups along the conical nanopore leads to the electrical rectification observed in the current-voltage (I-V) curve. On the contrary, other alkali cations are not able to induce any significant change in the rectification characteristics of the nanopore. The success of the chemical modification is monitored fr...

A proteolytic enzyme was produced by a strain of Lactobacillus brevis isolated from an oriental beverage. The enzyme was extracted and purified 50-fold by gel filtration and ion-exchange chromatography. The optimum pH for the enzyme was 7.0, the optimum temperature 35°C and the molecular weight 34,674 Da. Furthermore, the enzyme was stimulated by cations including Ca 2+ , Mg 2+ , Na + and K + and inhibited by Zn 2+ and Co 2+ ions. Other inhibitors were EDTA, ascorbic acid and citric acid. The enzyme is probably a neutral metalloprotease.

Microeconomics-inspired spectrum auctions can effectively improve the spectrum utilization for wireless networks to satisfy the ever increasing service demands. Considering the spatial reuse, the bidding nodes without mutual interference are grouped as virtual bidders competing for the spectrum bands, which turns a multi-winner spectrum auction into a traditional single-winner auction. To make the participating nodes bid truthfully, strategy-proof auctions are exploited to allocate the vacant spectrum bands. However, how to fairly allocate the profits of the virtual bidder among the winning bidders is still an imperative problem to solve. In this paper, we propose a Shapley Value based profit allocation (SPA) to distribute the profit among the bidding nodes according to their marginal contributions, which are both from helping the virtual bidder to win the auction and from generating the revenue during the auction period. Our simulation and analysis show that SPA can effectively integrate the contributions from the two stages in the spectrum auction and fairly allocate the profit among the winning bidders.

Cycloparaphenylenes (CPPs) have attracted wide attention because of their interesting properties owing to distorted and strained aromatic systems and radially oriented p orbitals. For application of CPPs, information on their charged states (radical cation and radical anion) is essential. Here, we measured absorption spectra of the radical cations and the radical anions of CPPs with various ring sizes over a wide spectral region by means of radiation chemical methods. The peak position of the near-IR bands for both the radical cation and the radical anion shifted to lower energies with an increase in the ring size. This trend is contrary to what is observed for transitions between the HOMO and LUMO of the neutral CPP. The observed spectra of the CPP radical ions were reasonably assigned based on time-dependent density functional theory. These results indicate that the next HOMO and the next LUMO levels are important in the electronic transitions of radical ions.

The study area is located in the Kano Municipal. It is bounded by latitudes 11°51´ to 12°06´N and longitudes 8°23´ to 8°38´ E covering an area of about 770.063 Km 2. It lies on the average altitude of 478m above sea level, and is generally undulating lowland. The relief is greatly influenced by the geology; characterized by small, blocky and low laying outcrops. Twenty (20) samples of groundwater collected from the study area from both deep (about 200m) and shallow boreholes, following the standard procedure as prescribed by APHA Guidelines. The analysis was achieved using Atomic Absorption Spectrometer (AAS-Varian AA240Fs), Direct reading Photometer (Hanna model), Titrimetric method, and Flame photometer (FPF9 Jenwy model).The interpretation of groundwater chemistry of the samples suggest that most of the samples analysed are within the WHO and Nigerian Standards for drinking, while some have concentrations beyond desirable limits. However, the concentrations of some elements such as Pb, above permissible limits in the samples analyzed have created a concern over the suitability of the water for drinking and other domestic uses. The assessment of water for irrigation indicates that most of the samples are suitable for irrigational purposes. The result of the laboratory analysis revealed that the selected ions were present in varying concentrations in the study area. The chemical parameters of water samples from the boreholes were plotted using AquaChem and revealed interaction between the groundwater and aquifer materials, and identified important data trends and groupings.

Ionothermal synthesis is a little used method for the preparation of coordination polymers. By this method, two cadmium compounds were synthesized, 1, with formula Cd3(ox)F2(Ina)2 (Ina = isonicotinate) and 2, Cd(NO3)2(4,4′-Bpy) (4,4′-Bpy = 4,4′-Bipyridine). The modification of the reaction conditions has allowed to obtain 2 as a pure phase. The structure of both compounds was determined by a single-crystal X-ray diffraction. Compound 1 is isostructural to the previously reported Cd2Zn(ox)(OH)2(Ina)2. It crystallizes in the monoclinic space group P21/n and present a three-dimensional (3D) network, built-up from [Cd3(ox)F2]n2n+ layers, linked by isonicotinate ligands. Crystals of 2 are formed by twins of two components which are rotated ca. 180° to each other. This compound crystallizes in the triclinic P-1 space group and its structure can be describe as a two-dimensional (2D) 4 connected ‘sql’ net. The layers are composed by [Cd(NO3)2]n chains linked through 4,4′-Bpy ligands, and ar...

Exploring an unknown environment with multiple robots requires an efficient coordination method to minimize the total duration. A standard method to discover new areas is to assign frontiers (boundaries between unexplored and explored accessible areas) to robots. In this context, the frontier allocation method is paramount. This paper introduces a decentralized and computationally efficient frontier allocation method favoring a well balanced spatial distribution of robots in the environment. For this purpose, each robot evaluates its relative rank among the other robots in term of travel distance to each frontier. Accordingly, robots are allocated to the frontier for which it has the lowest rank. To evaluate this criteria, a wavefront propagation is computed from each frontier giving an interesting alternative to path planning from robot to frontiers. Comparisons with existing approaches in computerized simulation and on real robots demonstrated the validity and efficiency of our algorithm.

We present here the case of a continuous ambulatory peritoneal dialysis (CAPD) patient who developed sclerosing calcifying peritonitis with gross macroscopic calcification of the small bowel, a rare and life-threatening complication of sclerosing peritonitis. A 40-year-old female had been on CAPD for 7 years. A peritoneal biopsy during an open cholecystectomy for cholelithiasis showed sclerosing peritonitis, but the patient refused to change dialysis modality. She remained free of symptoms for 3 years, but then was admitted with cloudy effluent, abdominal pain, and referred pain to the left shoulder. A white blood cell count showed 25,000 cells/microL, and a peritoneal cell count showed 1000 cells/microL. An abdominal computed tomography scan was nondiagnostic. The patient was started on intraperitoneal antibiotics, but 3 days later she was taken for surgery because of acute abdomen. Laparotomy revealed a tanned and thickened peritoneum and a small bowel with significant fibrosis an...

between face-to-face energetically stable {111} surface-bound pyrrolidone groups through Na + ion induced cation- interaction. Congested interplanner space between AgNPrs allows As(III) to react differentially with silver atoms from facial {111} and peripheral {110} facets to results smaller stacking and finally to nanoseeds. Above this critical concentration of As(III), PVP leached-out from nanoparticles to form nanoseed engulfed emulsions and inducing controlled aggregation. This entire morphological transition has been decoded by recording their plasmon and SERS tuning and confirmed by TEM study. Strong affinity and selectivity of As(III) towards Ag atom (verified and estimated by HF/3-21g* level of DFT calculation) coupled with low-cost colorimetry provide us a versatile assay with potential application in the environmental protection drive.

Reduced tubular cation transport in diabetes: Prevented by situated in the basolateral membrane of proximal tubular ACE inhibition. cells. In the rat kidney, organic cation transporters (OCTs) Background. The renal clearance of organic cations is imsituated in the S 1 and S 2 segments (OCT-1) and in S 2 and portant for the homeostasis of a number of exogenous and S 3 segments (OCT-2) of the proximal tubule are responsiendogenous compounds. The organic cation transporters (OCTs) ble for the first step in active cation secretion [1-3]. OCTs situated on the basolateral surface of proximal tubular cells are necessary for the renal clearance of a broad range of mediate active cation excretion. Alterations of cation transport may occur in diabetes, although the role of the OCTs has not substrates, including drugs (e.g., metformin, ␤ blockers), been previously assessed. toxins, and xenobiotics. OCTs are also important for the Methods. Experimental diabetes was induced in rats with renal homeostasis of a number of endogenous compounds, streptozotocin (55 mg/kg) and animals were randomly assigned including monoamine neurotransmitters, N-methyl-nicoto receive ramipril (3 mg/mL) in drinking water for 24 weeks. tinamide (NMN), creatinine, choline, cortisol, and pros-In a second protocol, rats were infused with angiotensin II taglandins (PGE 2 , PGF 2-␣) [2-5]. (Ang II) at a dose of 58.3 ng/kg/min for 2 weeks via an implanted osmotic pump. Expression of the OCTs and renal clear-Diabetic nephropathy is characterized by early impairance of the endogenous cation N-methyl-nicotinamide (NMN) ment of proximal tubular function with disruption of was assessed. tubular acidification [6] and lysosomal degradation [7]. Results. Diabetes was associated with a reduction in gene However, the effect of diabetes on OCT is unclear. Reand protein expression of both OCT-1 and OCT-2 and a reducduced accumulation of cationic nephrotoxins (including tion in NMN clearance. These effects were prevented by ramicephalordine [8] and cisplatin [9] in experimental diabepril, associated with the prevention of albuminuria and tubular injury as demonstrated by the expression of osteopontin and tes) has been attributed to impaired transporter pathglutathione peroxidase 3 (GPX-3). An infusion of Ang II also ways, contributing to "renal protection" in these models. reduced NMN clearance but without altering the renal expres-Ex vivo studies using renal cortical slices have provided sion of OCTs. conflicting data, demonstrating both reduced [9], un-Conclusion. We hypothesize that reduced expression of changed [10], or even increased cation transport in dia-OCTs in diabetes may be a marker of tubular injury. However, betic animals [11]. These ambiguous results may repre-Ang II may also directly augment renal cation clearance independent of changes in transporter expression. Together these sent the limitations of slice studies in the evaluation of effects may provide additional mechanism to explain treatsolely basolateral cation uptake, particularly in an in ment-related improvements in creatinine clearance and renovivo context. Given the clinical importance of the cation protection in diabetes following blockade of the renin-angiotransporter system, we have undertaken to examine the tensin system (RAS). expression and regulation of OCTs in diabetic nephropathy. Furthermore, we explored the link of cation transport to the renin-angiotensin system (RAS), a pathway Transepithelial clearance of small cationic molecules that has been implicated in pathogenesis of progressive is mediated in the kidney by electrogenic transporters tubulointerstitial injury in experimental diabetes.

Dinuclear N-heterocyclic dicarbene gold(I) complexes of general formula [Au 2 (RIm-Y-ImR) 2 ](PF 6) 2 (R = Me, Cy; Y = (CH 2) 1−4 , oxylylene, m-xylylene) have been synthesized and screened for their luminescence properties. All the complexes are weakly emissive in solution whereas in the solid state some of them show significant luminescence intensities. In particular, crystals or powders of the complex with R = Me, Y = (CH 2) 3 exhibit an intense blue emission (λ max = 450 nm) with a high quantum yield (Φ em = 0.96). The X-ray crystal structure of this complex is characterized by a rather short intramolecular Au•••Au distance (3.272 Å). Time dependent density functional theory (TDDFT) calculations have been used to calculate the UV/vis properties of the ground state as well as of the first excited state of the complex, the latter featuring a significantly shorter Au•••Au distance.

Using UV-vis spectroscopy in conjunction with various electrochemical techniques, we have developed a new effective operando methodology for investigating the oxygen reduction reactions (ORRs) and their mechanisms in nonaqueous solutions. We can follow the in situ formation and presence of superoxide moieties during ORR as a function of solvent, cations, anions, and additives in the solution. Thus, using operando UV-vis spectroscopy, we found evidence for the formation of superoxide radical anions during oxygen reduction in LiTFSI/diglyme electrolyte solutions. Nitro blue tetrazolium (NBT) was used to indicate the presence of superoxide moieties based on its unique spectral response. Indeed, the spectral response of NBT containing solutions undergoing ORR could provide a direct indication for the level of association of the Li cations with the electrolyte anions.

Two conformational isomers of the aromatic hydrocarbon n-butylbenzene have been studied using two-color MATI (mass analyzed threshold ionization) spectroscopy to explore the effect of conformation on ionization dynamics. Cationic states of gauche-conformer III and anti-conformers IV were selectively produced by two-color excitation Via the respective S 1 origins. Adiabatic ionization potentials of the gauche-and anticonformations were determined to be 70146 and 69872 (5 cm-1 respectively. Spectral features and vibrational modes are interpreted with the aid of MP2/cc-pVDZ ab initio calculations, and ionization-induced changes in the molecular conformations are discussed. Complete basis set (CBS) ab initio studies at MP2 level reveal reliable energetics for all four n-butylbenzene conformers observed in earlier two-color REMPI (resonance enhanced multiphoton ionization) spectra. For the S 0 state, the energies of conformer III, IV and V are above conformer I by 130, 289, 73 cm-1 , respectively. Furthermore, the combination of the CBS calculations with the measured REMPI, MATI spectra allowed the determination of the energetics of all four conformers in the S 1 and D 0 states.

Functionalization of a methylviologen with four methyl ester substituents significantly facilitates the first two reduction steps. The easily generated radical cation showed markedly improved air stability compared to the parent methylviologen, making this derivative of interest in organic electronic applications.

The aromatic methylene blue cation (MB(+)) shows unprecedented ligand behavior in the X-ray structures of the trigonal-planar (TP) complexes MBMCl2 (M = Cu(I), Ag(I)). The two isostructural compounds were exclusively synthesized by grinding together methylene blue chloride and MCl solids. Only in the case of AuCl did the technique lead to a different, yet isoformular, Au(I) derivative with separated MB(+) and AuCl2(-) counterions and no direct N-Au linkage. While the density functional theory (DFT) molecular modeling failed in reproducing the isolated Cu and Ag complexes, the solid-state program CRYSTAL satisfactorily provided for Cu the correct TP building block associated with a highly compact π stacking of the MB(+) ligands. In this respect, the dispersion interactions, evaluated with the DFT functional, provide to the system an extra energy, which likely supports the unprecedented metal coordination of the MB(+) cation. The feature seems governed by subtle chemical factors, such...

In this work we evaluated the energetic interactions between imidazolium ionic liquids (ILs) and hydrofluoric acid, as well as the cation-anion interactions in ILs. We used DFT calculations that include dispersion corrections employing the PBE and M06 functionals. We tested twenty-two ILs, including [C4MIM] [PF6], [C4MIM] [NTf2] and [C4MIM] [CH3COO], obtaining interaction energies in the range of -27 to -13 kcal/mol with the PBE functional. The NCI (non-covalent interactions) index developed by Yang and collaborators (J. Am. Chem. Soc., 2010, 132, 6498-6506, J. Chem. Theory Comput. 2011, 7, 625-632) also was used for mapping the key non-covalent interactions (hydrogen bonds, van der Waals and steric repulsions) between the anions and cations of ILs and also for interactions of ILs with hydrofluoric acid (HF). The results obtained show that the anions have a stronger effect with respect to cations in their capacity for interacting with hydrofluoric acid, and the strongest interaction...

The effectiveness of the treatment of pathogens disease in fish using chemicals is very limited because of the stress of toxic ions. A treatment of humic acid of 50-90 mg /L on a farmland has been able to reduce illness and death compared to a mixture of formaldehyde and blue-green methylene. Humic acid is suspected to be able to increase yield, through improved conditions and resistance to diseases, health, and cultural vitality, either by itself or combined with cation species toxic. Humic acid can balance the soil cation so that the soil pH reached 7-8, through a chelate of Al, Fe, Ca or exchanged with NH4, Na and K. Humic acids were extracted from compost plants with a weak base of 0.1 N NaOH and precipitated at pH 2. The concentration of AH 0-400 ml was applied to three soil types with an area of 0.12 m 2 and 15 cm thickness. The results showed that the application of 100-200 ml HA/0.12 m 2 gave optimum yield in improving the physical-chemical characteristics of the soil embankment. Soil pH reached a value of 7-8, cation exchange to 60% saturated, and soil bulk density was reached in the range of 1.1-0.97 g / cm 3 .This condition is suitable for fish or shrimp in the embankment.

Cation diffusion facilitators (CDF) are part of a highly conserved protein family that maintains cellular divalent cation homeostasis in all domains of life. CDF's were shown to be involved in several human diseases, such as Type-II diabetes and neurodegenerative diseases. In this work, we employed a multidisciplinary approach to study the activation mechanism of the CDF protein family. For this we used MamM, one of the main ion transporters of magnetosomes-bacterial organelles that enable magnetotactic bacteria to orientate along geomagnetic fields. Our results reveal that the cytosolic domain of MamM forms a stable dimer that undergoes distinct conformational changes upon divalent cation binding. MamM conformational change is associated with three metal binding sites that were identified and characterized. Altogether, our results provide a novel auto-regulation mode of action model in which the cytosolic domain's conformational changes upon ligand binding allows the priming of the CDF into its transport mode.

1-methylpyrene radical cations undergo the loss of a hydrogen atom at internal energies above the first dissociation threshold. Imaging photoelectron photoion coincidence spectroscopy was employed in combination with RRKM modelling to determine a 0-K activation energy of 2.78 ± 0.25 eV and an entropy of activation of 6 ± 19 J K-1 mol-1 for this H-loss reaction. The ionization energy of 1methylpyrene was measured by mass-selected threshold photoelectron spectroscopy to be 7.27 ± 0.01 eV. These values were found to be consistent with calculations at the CCSD/6-31G(d)//B3-LYP/6-31G(d) level of theory showing that the formation of the 1-methylenepyrene cation (resulting from H loss from the methyl group) is kinetically more favorable than the formation of a tropylium-containing product ion that is structurally analogous to the formation of the tropylium cation in H loss from ionized toluene. The shift away from a tropylium-containing structure was found to be due to the increased ring-strain imposed on the C7 moiety when it is bound to three fused benzene rings. The RRKM results allow for the derivation of the ∆ f H 0 o (1-methylenepyrene cation) of 945 ± 31 kJ mol-1 .

Ionothermal synthesis is a little used method for the preparation of coordination polymers. By this method, two cadmium compounds were synthesized, 1, with formula Cd 3 (ox)F 2 (Ina) 2 (Ina = isonicotinate) and 2, Cd(NO 3) 2 (4,4-Bpy) (4,4-Bpy = 4,4-Bipyridine). The modification of the reaction conditions has allowed to obtain 2 as a pure phase. The structure of both compounds was determined by a single-crystal X-ray diffraction. Compound 1 is isostructural to the previously reported Cd 2 Zn(ox)(OH) 2 (Ina) 2. It crystallizes in the monoclinic space group P2 1 /n and present a three-dimensional (3D) network, built-up from [Cd 3 (ox)F 2 ] n 2n+ layers, linked by isonicotinate ligands. Crystals of 2 are formed by twins of two components which are rotated ca. 180 • to each other. This compound crystallizes in the triclinic P-1 space group and its structure can be describe as a two-dimensional (2D) 4 connected 'sql' net. The layers are composed by [Cd(NO 3) 2 ] n chains linked through 4,4-Bpy ligands, and are pillared along the [011] direction. The thermal decomposition of 2 was studied by thermogravimetric and thermodiffractiometric techniques. The compound decomposes gradually starting from 160 • C, and due to heating, the structure suffers slight reversible changes in the bond distances and angles.

Why does my program crash?"-This ever recurring question of software debugging drives the developer during the analysis of the failure. Complex defects are impossible to automatically identify; this can only be left to human judgment. But what we can do is empower the developer to make an informed decision, by helping her understand the failure. To fully comprehend a failure, one may need to consider many different aspects such as the range of the input parameters and the program's structure and runtime behavior. I propose an approach that gathers a variety of such facts from a given failing execution. To examine the correlation of those facts to the failure, it produces additional executions that differ in as few facts as possible. Then the approach creates generalizations and abstractions over the correlating facts. These explain different aspects of the failure and thus help the developer understand and eventually fix the underlying defect.

Prirodne vode, podzemne i površinske, često sadržavaju povišene koncentracije prirodnih organskih tvari (NOM). Prirodne organske tvari dospijevaju u vode ispiranjem tla ili biološkom razgradnjom biljnih i životinjskih materijala u vodi. Najznačajnija komponenta prirodnih organskih tvari su humusne tvari. Humusne tvari su nepoželjne u vodi jer vodi daju boju, okus i miris te na sebe vežu različite kontaminante (teške metale, pesticide). Naročito značajan problem predstavljaju povedane koncentracije humusnih tvari u vodi pri dezinfekciji vode klorom pri čemu nastaju štetni halogenirani nusprodukti trihalogenmetani (THM) koji djeluju toksično i kancerogeno na ljudski organizam. Humusne tvari su kompleksna smjesa spojeva koji se razlikuju po strukturi, molekularnoj težini, boji i poziciji funkcionalnih skupina, ovisno o porijeklu i starosti organskog materijala, vrsti vode, ekološkim i klimatskim uvjeta što rezultira i različitom reaktivnošdu s klorom, odnosno različitim njihovim potenc...

The reaction of uranyl ions with azelaic or dodecanedioic acids under solvohydrothermal conditions leads to crystallization of anionic dinuclear cage compounds with [M(bipy/phen) 3 ] 2+ counterions (M = 3dblock cation), while the smaller suberic acid yields heterometallic metallacycles. Complexes with the longer aliphatic chains are the first triple-stranded helicates reported in actinide chemistry.

FprA, a Mycobacterium tuberculosis NADPH-ferredoxin reductase, consists of two structural domains, a FAD-binding and a NADP-binding domain, respectively. For the first time, we demonstrated that native FprA, on thermal treatment underwent partial denaturation with unfolding of only the FAD-binding domain and release of the protein-bound flavin. The NADP-binding domain of this protein is highly resistant to denaturation under these conditions. However, the presence of either 150 mM NaCl or KCl or 10 M MgCl 2 or CaCl 2 or slightly acidic pH of 6.0 resulted in a highly cooperative and complete thermal unfolding of the protein. Physicochemical investigations showed that the monovalent cations or low concentrations of divalent cations induced compaction of the protein conformation. However, divalent cations at higher concentrations resulted in FAD release leading to stabilization of an enzymatically inactive apo-enzyme. Detailed thermal denaturation studies on the native protein and the isolated NADP-binding domain showed that cations and pH 6.0 destabilized only the heat-stable NADP-binding domain. The experimental studies demonstrate that modulation of intramolecular ionic interactions induce significant conformational changes in the NADP-binding domain of FprA, resulting in a substantial increase in the structural cooperativity of the whole molecule. The results presented in this paper are of importance as they demonstrate alterations in the native three-dimensional structure of FprA and cooperativity in protein molecule on slight alteration of pH or modification of ionic interactions in protein.

between face-to-face energetically stable {111} surface-bound pyrrolidone groups through Na + ion induced cation- interaction. Congested interplanner space between AgNPrs allows As(III) to react differentially with silver atoms from facial {111} and peripheral {110} facets to results smaller stacking and finally to nanoseeds. Above this critical concentration of As(III), PVP leached-out from nanoparticles to form nanoseed engulfed emulsions and inducing controlled aggregation. This entire morphological transition has been decoded by recording their plasmon and SERS tuning and confirmed by TEM study. Strong affinity and selectivity of As(III) towards Ag atom (verified and estimated by HF/3-21g* level of DFT calculation) coupled with low-cost colorimetry provide us a versatile assay with potential application in the environmental protection drive.

Room-temperature phosphorescence (RTP) has a much longer lifetime than fluorescence as it involves triplet excitons. This extended lifetime enables the design of advanced optoelectronics and biological sensing technologies. Despite the omnipresence of triplet states, harnessing these triplet excitons remains challenging for most organic materials due to the forbidden transitions between singlet and triplet states. Here we report novel organic-inorganic hybrid perovskites based on conjugated organic cations with low-lying triplet energy levels to extract triplet excitons from the inorganic component, thereby generating RTP with long lifetime in millisecond range. Dexter type energy transfer was confirmed to occur in this type of hybrid perovskites with transfer efficiency of up to 80%. More impressively, multiplecolored phosphorescence was achieved by facile design of the system using organic cations with different triplet exciton energies. These results are expected to greatly expand the prospects of hybrid perovskites with functional organic cations for versatile display applications.

Anion and cation emission following water dissociation was studied for 6.6-keV 16 O + + H2O collisions. Absolute cross sections for the emission of all positively and negatively charged fragments, differential in both energy and observation angle, were measured. The fragments formed in hard, binary collisions appearing in peaks were distinguishable from those created in soft collisions with many-body dynamics that result in a broad energy spectrum. A striking feature is that anions and cations are emitted with similar energy and angular distributions, with a nearly constant ratio of about 1:100 for Hto H +. Model calculations were performed at different levels of complexity. Four-body scattering simulations reproduce the measured fragment distributions if adequate kinetic-energy release of the target is taken into account. Providing even further insight into the underlying processes, predictions of a thermodynamic model indicate that transfer ionization at small impact parameters is the dominant mechanism for H + creation. The present findings confirm our earlier observation that in molecular fragmentation induced by slow, singly charged ions, the charge states of the emitted hydrogen fragments follow a simple statistical distribution independent of the way they are formed.

The electrochemical reduction of the extended 1,1′-bipyridinium dication was investigated in detail by means of semiquantitative in situ electron paramagnetic resonance (EPR), UV−vis−NIR spectroelectrochemistry, and density functional theory (DFT) calculations. It was found that in the extended 1,1′-bipyridinium cation radical the spin density is localized on one of the pyridinium centers, which is in contrast to charge delocalization within the 4,4′-bipyridinium radical cation reported in the literature. The charge and spin density separation in the extended 1,1′-bipyridinium cation radical leads to π-dimer formation in a triplet electronic configuration.

A microsomal fraction possessing Mg2+-dependent and K+-stimulated ATPase activity was extracted by differential centrifugation from roots of grape seedlings (Vitis vinifera L. cv. Verduzzo). Roots yield from grape seeds was stimulated by means of GA3 and further improved by treatments able to control microbial contamination. The biochemical characteristics of ATPase activity were studied and compared with those previously reported for roots produced by grape woody cuttings. The presence of choline-Cl, ethanolamine and glycerol-1-P in addition to BSA, EDTA, PVPP and DTT in the homogenizing medium was obligatory in order to record the K+-stimulated component of activity. The enzyme was activated by Mg2+, further stimulated by monovalent ions and showed strong preference for ATP as the substrate and optimum pH at 6.5 in the presence of both Mg2+ and K+. The effect of different monovalent ions followed a sequence similar to that found in cereal roots preparations, but very different wit...

Resorc[4]arenes 1 and 2, which previously proved to entrap NO + cation within their cavities under conditions of host-to-guest excess, were treated with a 10-fold excess of NOBF 4 salt in chloroform. Kinetic and spectral UV−visible analyses revealed the formation of isomeric 1:2 complexes as a direct evolution of the previously observed event. Accordingly, three-body 1−(NO +) 2 and 2−(NO +) 2 adducts were built by MM and fully optimized by DFT calculations at the B3LYP/ 6-31G(d) level of theory. Notably, covalent nitration products 4, 5 and 6, 7 were obtained by reaction of NOBF 4 salt with host 1 and 2, respectively, involving macrocycle ring-opening and insertion of a nitro group in one of the four aromatic rings. In particular, compounds 4 and 6, both containing a trans-double bond in the place of the methine bridge, were oxidized to aldehydes 5 and 7, respectively, after addition of water to the reaction mixture. Calculation of the charge and frontier orbitals of the aromatic donor (HOMO) and the NO + acceptor (LUMO) clearly suggests an ipso electrophilic attack by a first NO + unit on the resorcinol ring, mediated by the second NO + unit.

We have investigated, both theoretically and experimentally, the balance between the presence of alkyl and perfluoroalkyl side chains on the surface organization and surface tension of fluorinated ionic liquids (FILs). A series of ILs composed of 1-alkyl-3-methylimidazolium cations ([CnC1im] with n = 2, 4, 6, 8, 10 or 12) combined with the perfluorobutanesulfonate anion was used. The surface tensions of the investigated liquid salts are considerably lower than those reported for non-fluorinated ionic liquids. The most surprising and striking feature was the identification, for the first time, of a minimum at n = 8 in the surface tension versus the length of the IL cation alkyl side chain. Supported by molecular dynamic simulations it was found that this trend is a result of the competition between the two nonpolar domains (perfluorinated and aliphatic) on pointing towards the gas-liquid interface, a phenomenon which occurs in ionic liquids with perfluorinated anions. Furthermore, th...

The well-studied hydrogen sulfide molecule is shown here for the first time to form a S−S bond barrierlessly with sulfur atomic cation to produce stable H SS + , a compound for which there is nearly no literature data. Previous work has shown that the reaction of hydrogen sulfide with neutral atomic sulfur will likely only take place at high pressures. Conversely, this work shows that hydrogen sulfide will readily bind with atomic sulfur cation first through the 1 4 A state from association of H 2 S with S + (4 S) and then will relax down to the nearly degenerate 1 2 A or 1 2 A states. S + (4 S) + H 2 S lies 29.5 kcal/mol above the 1 4 A H 2 SS + minimum. The 1 4 A H 2 SS + minimum in the S−S bond is also directly intersected by the doublet potential energy surface. As the S−S bond shortens in the association, the 1 2 A and 1 2 A states split falling 33.5 kcal/mol and 26.4 kcal/mol, respectively, below the 1 4 A state. Hence, this work is opening the door for novel synthesis of S−S bonds or potential removal of the common H 2 S toxin/pollutant through concatenation and subsequent precipitation.

Aqueous biphasic systems (ABS) are relevant for the development of environmentally friendly and "biocompatible" separation processes. However, the common polyethylene glycol (PEG) polymers present a limited range of applicability, due to the low polarity of the PEG-rich phase. To overcome this limitation, a new approach was recently proposed based on the use of ionic liquids (ILs) as adjuvants in ABS, enlarging the polarity range of these systems. This work addresses the use of imidazolium-based ILs as ionic adjuvant compounds in the formation of ABS, namely potassium salts + water + PEG (1500, 4000, 6000 and 8000). To explore the differences induced by the presence of the IL as adjuvant the partition behavior of two dyes, Chloranilic Acid and Rhodamine 6G, is analyzed and correlated with the phase behavior and the IL distribution on the ABS under study.

The neutrals of the Li n I (n = 2-6) clusters were detected using Knudsen-cell which was placed into ionization chamber of the magnetic sector mass spectrometer. The first theoretical and experimental data on the Li 3 I and Li 5 I clusters were presented in this Letter. The ionization energies of the neutral of Li 3 I and Li 5 I clusters, obtained by the electron impact ionization mass spectrometry, were (5.14 ± 0.25) and (4.62 ± 0.25) eV, respectively. We report the geometry, ionization energies and thermodynamical stability of these clusters, calculated at the restricted coupled cluster RHF-RCCSD/cc-pVTZ(Li), cc-pVTZ-PP(I) level of theory.

Some salts have been recently shown to decrease the SFG (sum frequency generation spectroscopy) intensity of the hydrogen-bonded water molecules, but a quantitative explanation is still awaited. Here we report a similar trend for the chloride salts of monovalent cations, i.e., LiCl, NaCl, and CsCl, at low concentrations. Specifically, we revealed not only the specific adsorption of cations at the water surface but also the concentration-dependent effect of ions on the SFG response of the interfacial water molecules. Our thin film pressure balance (TFPB) measurements (stabilized by 10 mM of methyl isobutyl carbinol) enabled the determination of the surface potential that governs the surface electric field affecting interfacial water dipoles. The use of the special alcohol also enabled us to identify a remarkable specific screening effect of cations on the surface potential. We explained the concentration-dependency by considering the direct ion-water interactions and water reorientation under the influence of surface electric field as the two main contributors to the overall SFG signal of the hydrogen-bonded water molecules. While the former was dominant only at low concentration range, the effect of the latter intensified with increasing salt concentration, leading to the recovery of the band intensity at medium concentrations. We discussed the likelihood of a correlation between the effect of ions on reorientation dynamics of water molecules and the broadband intensity drop in the SFG spectra of salt solutions. We proposed a mechanism for the cation-specific effect through the formation of an ionic capacitance at the solution surface. It explains how cations could impart the ion specificity while they are traditionally believed to be repelled from the interfacial region. The electrical potential of this capacitance varies with the charge separation and ion density at the interface. The charge separation being controlled by the polarizability difference between anions and cations was identified using the SFG response of the

The infrared spectrum of mass selected Li +-D 2 cations is recorded in the D-D stretch region (2860-2950 cm-1) in a tandem mass spectrometer by monitoring Li + photofragments. The D-D stretch vibration of Li +-D 2 is shifted by-79 cm-1 from that of the free D 2 molecule indicating that the vibrational excitation of the D 2 subunit strengthens the effective Li +-D 2 intermolecular interaction. Around 100 rovibrational transitions, belonging to parallel K a=0-0, 1-1, and 2-2 subbands, are fitted to a Watson A-reduced Hamiltonian to yield effective molecular parameters. The infrared spectrum shows that the complex consists of a Li + ion attached to a slightly perturbed D 2 molecule with a T-shaped equilibrium configuration and a 2.035 A vibrationally averaged intermolecular separation. Comparisons are made between the spectroscopic data and data obtained from rovibrational calculations using a recent three dimensional Li +-D 2 potential energy surface [R.

The Li +-(H 2) n n = 1-3 complexes are investigated through infrared spectra recorded in the H-H stretch region (3980-4120 cm −1) and through ab initio calculations at the MP2∕aug-cc-pVQZ level. The rotationally resolved H-H stretch band of Li +-H 2 is centered at 4053.4 cm −1 [a −108 cm −1 shift from the Q 1 (0) transition of H 2 ]. The spectrum exhibits rotational substructure consistent with the complex possessing a Tshaped equilibrium geometry, with the Li + ion attached to a slightly perturbed H 2 molecule. Around 100 rovibrational transitions belonging to parallel K a = 0-0, 1-1, 2-2, and 3-3 subbands are observed. The K a = 0-0 and 1-1 transitions are fitted by a Watson A-reduced Hamiltonian yielding effective molecular parameters. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 2.056 Å increasing by 0.004 Å when the H 2 subunit is vibrationally excited. The spectroscopic data are compared to results from rovibrational calculations using recent three dimensional Li +-H 2 potential energy surfaces [

The results of a combined zyncbrouon UV-radiation and convcntionsl XPS study on the (001) surface of a NaCN single crjmxl are rcponaim ALsolute valma and core binding energies of CN-are deduced_ The valence ektron s~ectnn of NaCN is shown to be dominated by cmiss~-on from the CN-sublattice. Satellite structure is found in the inner valence electron n&011 and consistently intapzeted in comparison with CO and N2_ The eqerimmtalIy de termined electronic structure is compare+i with many-bodyab initiocakuhions oflheiotitionspeanun of CN-_ No band stkture effects (k diqxsion) in the vakna qxctra are found due co the rotational disorder of the CN sublattioc T&c branching ratios of the outer valence k&s ~d~~and~pe~~~inbottoI~artobsenrrd'Tht~ergi~OftheSha~-~~~~-are compreduithgascous omdusai and adsorbed CO and N+_ ' Work nrpporred in Part by Bundesminkxerium f&r Forschung und Tcchnologic (BMFT) from funds for rexarch with syadlrotnnl mdiation * Rcsalt addrcss~ Ji.dlrstu!ll fii-l-lK!orctische chemic. uoivasita zu KaIn, Grrinnraac 4. Q-5000 cologne 4!. FRG. 'TovbomconxsPomlenceshould~sddre=L l Pamasunt addresk InstiFute for'M@cad% S&LXX. Myodaiji. O-444. Jzqxk-_ s &tmument addresx Department of Physis linkwing Uniwssity. ssg1g3 link*ing. Sweden pendence of the phdtoionization cross section since the observation of molecuiar shape resonances [3]_ It has been she-recently, that energetic position and intensity of such shape resonances are wnsid-. erably influenced by binding the fi-ee moJ+e tp a metal surface [1,4].. Firstly, this cquld be due to the change of-the potential felt by the escaping-eleIectron caused by ~a i-qiistribution _of @e yectron density upon bin$ling a molecule to +e surface, ie.

The electrochemical reduction of the extended 1,1′-bipyridinium dication was investigated in detail by means of semiquantitative in situ electron paramagnetic resonance (EPR), UV−vis−NIR spectroelectrochemistry, and density functional theory (DFT) calculations. It was found that in the extended 1,1′-bipyridinium cation radical the spin density is localized on one of the pyridinium centers, which is in contrast to charge delocalization within the 4,4′-bipyridinium radical cation reported in the literature. The charge and spin density separation in the extended 1,1′-bipyridinium cation radical leads to π-dimer formation in a triplet electronic configuration.