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Detection of nitroaromatic compounds (NAC) is an important task since these substances are hazardous to both the biosphere and the society. Fluorescent sensors developed for NAC detection usually demonstrate a ‘turn-off’ response to the analyte, while ‘turn-on’ sensors are rarely reported. Here, we present a showcase report on new pyrene-imidazoporphyrin dyads that demonstrate an unusual analytic response to NAC with clear ‘turn-on’ behavior followed by an unexpected appearance of a new band, which can be ascribed to exciplex emission. The porphyrin backbone of the dyad also allows registration of its own fluorescence, providing an internal reference signal for ratiometric detection. The association constants in the order of 104 M−1 are reported.

The development of flexible strain sensors over the past decade has focused on accessing high strain percentages and high sensitivity (i.e., gauge factors). Strain sensors that employ capacitance as the electrical signal to correlate to strain are typically restricted in sensitivity because of the Poisson effect. By employing auxetic structures, the limits of sensitivity for capacitive sensors have been exceeded, which has improved the competitiveness of this modality of sensing. In this work, the first employment of helical auxetic yarns as capacitive sensors is presented. It is found that the response of the helical auxetic yarn capacitive sensors (termed as HACS) is dependent on the two main fabrication variables-the ratio of diameters and the helical wrapping length. Depending on these variables, sensors that respond to strain with increasing or decreasing capacitance values can be obtained. A greater auxetic character results in larger sensitivities accessible at smaller strains-a characteristic that is not commonly found when accessing high gauge factors. In addition, the highest sensitivity for auxetic capacitive sensors reported thus far is obtained. A mechanism of sensor response that explains both the variable capacitance response and the high gauge factors obtained experimentally is proposed., Advanced Materials, 35 (10), ISSN:0935-9648, ISSN:1521-4095

The reliability of evolutionary reconstructions based on the fossil record critically depends on our knowledge of the factors affecting the fossilization of soft‐bodied organisms. Despite considerable research effort, these factors are still poorly understood. In order to elucidate the main prerequisites for the preservation of soft‐bodied organisms, we conducted long‐term (1–5 years) taphonomic experiments with the model crustacean Artemia salina buried in five different sediments. The subsequent analysis of the carcasses and sediments revealed that, in our experimental settings, better preservation was associated with the fast deposition of aluminum and silicon on organic tissues. Other elements such as calcium, magnesium, and iron, which can also accumulate quickly on the carcasses, appear to be much less efficient in preventing decay. Next, we asked if the carcasses of uni‐ and multicellular organisms differ in their ability to accumulate aluminum ions on their surface. The experiments with the flagellate Euglena gracilis and the sponge Spongilla lacustris showed that aluminum ions are more readily deposited onto a multicellular body. This was further confirmed by the experiments with uni‐ and multicellular stages of the social ameba Dictyostelium discoideum. The results lead us to speculate that the evolution of cell adhesion molecules, which provide efficient cell–cell and cell–substrate binding, probably can explain the rich fossil record of soft‐bodied animals, the comparatively poor fossil record of nonskeletal unicellular eukaryotes, and the explosive emergence of the Cambrian diversity of soft‐bodied fossils., We present the results of long‐term (1–5 years) taphonomic experiments with Artemia salina buried in different sediments. The results imply that fossil preservation of soft‐bodied organisms depends critically on fast deposition of Al and Si ions and that the evolution of cell adhesion molecules in the early multicellular organisms probably played an important role in the sudden appearance of diverse fossil record of multicellular soft‐bodied organisms around the Precambrian/Cambrian boundary.

In this paper, we study the possibility of using a certain cloud computing model supplied with cryptoservers to obfuscate software programs. Earlier, we proposed this cloud computing model in our study of some information security problems for multi-client distributed computing over encrypted data. Based on this model, we proposed a new approach involving the use of threshold homomorphic cryptosystems for program obfuscation. The main result of this paper is a new definition of the resistance of obfuscation of programs in the cloud computing model and a theorem proving the cryptographic strength of the proposed algorithm of obfuscation of programs under the assumption of the existence of cryptographically strong threshold homomorphic encryption systems. The paper is organized as follows. In the introducing section we discuss the main aspects of the information security problems for cloud computing systems. Section 2 provides a description of the obfuscation program objectives, as well as a brief overview of the main achievements in its study. The next section provides general information about homomorphic cryptosystems. Section 4 describes a more special class of homomorphic cryptosystems - threshold homomorphic encryption systems. Section 5 introduces the cloud computing model, which is used as a framework for our program obfuscation techniques. For this computing environment, in Section 6, the definition of the cryptographic strength of program obfuscation is formulated, a new method of program obfuscation using threshold homomorphic cryptosystems is described, and the cryptographic strength of the proposed obfuscation algorithm is proved.

New di- and tetrasubstituted thiacalix[4]arenes in cone and 1,3-alternate configurations containing terpyridine and triazole fragments at the lower rim of the macrocycle, as well as model triazole-terpyridine, are synthesized. The structures and purity of the compounds are confirmed by NMR spectroscopy and high-resolution MALDI mass spectrometry. The compounds form luminescent complexes with lanthanide cations (europium and terbium) in a chloroform-methanol (10: 1) system during fluorimetric titration. The possibility of antenna ef ect during fluorescence sensitization in lanthanides by the thiacalixarene ligands is demonstrated. Successful immobilization of the terpyridine receptors on a solid substrate makes it possible to consider the Langmuir-Blodgett films on the basis of these receptors as promising adsorbents of lanthanide from nonaqueous media or organic salts and also provides new opportunities for the investigation of the luminescence characteristics of lanthanide complexes in thin films.

Langmuir 36(6), 1423 - 1429 (2020). doi:10.1021/acs.langmuir.9b03403, Redox isomerism, that is, the change of a metal cation valence state in organic complexes, can find promising applications in multistable molecular switches for various molecular electronic devices. However, despite a large number of studies devoted to such processes in organic complexes of multivalent lanthanides, redox-isomeric transformations were never observed for europium. In the present work, we demonstrate the unique case of redox isomerization of Eu(III)/Eu(II) complexes on the example of Eu double-decker octa-n-butoxyph- thalocyaninate (Eu[(BuO)8Pc]2) under ambient conditions (air and room temperature). It is shown that assumption of the face-on orientation on the aqueous subphase surface, in which two of each phthalocyanine decks in Eu[(BuO)8Pc]2 are located in different media (air and water), leads to the intramolecular electron transfer that results in the formation of a divalent Eu(II) cation in the complex. Lateral compression of the thus-formed monolayer results in the reorientation of bisphthalocyaninate to the edge-on state, in which the ligands can be considered identical, and occurrence of the reverse redox-isomeric transformation into the complex with a trivalent Eu cation. Both redox-isomeric states were directly observed by X-ray absorption near-edge structure spectroscopy in ultrathin films formed under different conditions., Published by ACS Publ., Washington, DC

Designing sensors for toxic compounds such as mercury salts in aqueous solutions still remains one of the most pressing tasks of modern chemical research, since many existing systems do not show enough sensitivity and/or response. In this regard, the opportunities offered by supramolecular approaches can be used to improve both these characteristics by creating a new self-organized smart system. Herein, we show that barium cations, that according to the data of X-ray standing waves do not bind directly to the ionophore molecules in the monolayers at the air/water interface, could be used to efficiently preorganize such molecules to achieve supramolecular architecture. We demonstrate that such preorganization ensures both low analyte detection threshold and high fluorescent response. We reveal the interrelation of the monolayer structure and receptor characteristics of a sensory system and show that such cation-induced preorganization in Langmuir monolayers of a hemicyanine dithia-aza-crown-substituted chromoionophore inhibits the formation of non-fluorescent aggregates with low receptor function, and allows the quantitative detection of mercury cations using a ratiometric fluorometric approach.

In the present work, we investigate, by means of in situ UV-Vis reflection-absorption spectroscopy and X-ray reflectivity measurements, the effect of the mercury ion analyte on the supramolecular structure of the dithia-azacrown-hemicyanine chromoionophore Langmuir monolayers upon their interaction at the air/water interface. It was revealed that while Hg2+ ions are not able to form complexes with ionophore crown ether groups and do not perturb the organization of the monolayer at low analyte concentrations, high enough concentrations lead to the change of its structure. Supramolecular architecture of the monolayer attains a type identical to the one observed in the case of analyte-binding by the barium-preorganized monolayer. Presented study brings further insight into this preorganization phenomenon.

International audience; This work deals with the development of ultra-thin film nanosensors for selective and sensitive detection of toxic Hg2+ cations in aqueous media. 1,8-Bis[(2-aminoethyl)amino]anthraquinone D0 was functionalized by alkoxy groups of different length to prepare ligands D3 and D12 with linear arrangement of two polyamine receptors and two lipophilic alkyl chains. Chemosensor D0 only binds copper(II) and mercury(II) cations in water/methanol (1:1 v/v) solutions with no interference by other metal cations. The introduction of alkoxy groups to the anthraquinone scaffold, which are required to form Langmuir monolayers and ultra-thin films on solid supports, does not change the sensing properties of the anthraquinone D0. In contrast to systems without specific molecular order (i.e. solutions and drop-cast films), Langmuir monolayers and ultra-thin Langmuir-Blodgett films of alkoxy-substituted ligands selectively bind only mercury(II) cations, even in the presence of copper(II) ions and 10 other interfering cations. Selective binding of mercury(II) cations was confirmed by the UV–vis absorption and X-ray fluorescence spectroscopies. Thus, ultra-thin films, in which chemosensor molecules are assembled in highly ordered supramolecular systems, display a higher selectivity as compared to that of disordered molecular systems. Ultra-thin sensory film allows for the selective detection of Hg2+ ions in water when their concentration is exceeded 0.01 μM, which corresponds to the action level for Hg2+ ions in drinking water recommended by the U.S. Environmental Protection Agency. Chemosensor D12 is also suitable for the fabrication of electrochemical sensors for mercury(II) cations that show similar sensitivity.

Achievement of information storage at molecular level remains a pressing task in miniaturization of computing technology. One of the promising approaches for its practical realization is development of nanoscale molecular switching materials including redox-active systems. The present work demonstrates a concept of expansion of a number of available redox-states of self-assembled monolayers through supramolecular approach. For this, the authors synthesized an octopus-like heteroleptic terbium(III) bisphthalocyaninate bearing one ligand with eight thioacetate-terminated "tentacles" (octopus-Pc) and a ligand with four crown-ether moieties (H2 [(15C5)4 Pc]). It is shown that octopus-Pc forms stable monolayers on gold, where its face-on orientation allows for subsequent binding of crown-phthalocyanine molecules via potassium ion bridges. This chemistry is utilized to form a heterogeneous bilayer, in which a single molecule thick adlayer brings an additional redox-state to the system, thus expanding the multistability of the system as a whole. All four redox states available to this system exhibit characteristic absorbance in visible range, allowing for the switching to be easily read out using optical density measurements. The proposed approach can be used in wide range of switchable materials-single-molecule magnets, conductive, and optical devices, etc.

Coordination-induced spin crossover (CISCO) in nickel(II) porphyrinates is an intriguing phenomenon that is interesting from both fundamental and practical standpoints. However, in most cases, realization of this effect requires extensive synthetic protocols or extreme concentrations of extra-ligands. Herein we show that CISCO effect can be prompted for the commonly available nickel(II) tetraphenylporphyrinate, NiTPP, upon deposition of this complex at the air/water interface together with a ruthenium(II) phthalocyaninate, CRPcRu(pyz)2, bearing two axial pyrazine ligands. The latter was used as a molecular guiderail to align Ni···Ru···Ni metal centers for pyrazine coordination upon lateral compression of the system, which helps bring the two macrocycles closer together and forces the formation of Ni–pyz bonds. The fact of Ni(II) porphyrinate switching from low- to high-spin state upon acquiring additional ligands can be conveniently observed in situ via reflection-absorption UV-vis spectroscopy. The reversible nature of this interaction allows for dissociation of Ni–pyz bonds, and thus, change of nickel cation spin state, upon expansion of the monolayer.

The work presents the results of a study of the negative photochromism and luminescent properties of 1',3'-dihydro-3',3'-dimethyl-6-nitro-1'-octadecyl-[1-benzopyran-2,2'-indole]-8-methyl pyridinium chloride (SP2) in solutions, Langmuir monolayers, and cast films. It has been demonstrated that the introduction of the pyridine substituent into the chromene part of the amphiphilic spiropyran leads to stabilization of the open form of the compound under dark conditions, both in the dissolved and in the ordered planar state. The kinetic characteristics of photoreactions occurring in organic solvents upon irradiation by visible light and during relaxation in darkness are determined. Negative solvatochromism of SP2, which consists in the hypsochromic shift of the maximum absorption of the merocyanine form of the compound upon increase of the solvent polarity, is revealed. The luminescent properties of solutions of negative spiropyran and its cast films are investigated. For the first time, SP2 monolayers are formed at the air/water interface and their properties are studied. It is established that SP2 retains its photochromic properties upon transition from solutions to a two-dimensional condensed state. The results obtained open up broad prospects for the development of switchable optoelectronic and information systems based on negative spiropyrans.

New derivatives of 2-(4-vinylchromen-2-ylidene)malononitrile and 2-(2-vinylchromen-4-ylidene)malononitrile were synthesized using the Knoevenagel reaction of 2-(4-methyl-chromen-2-ylidene)malononitrile and 2-(2-methylchromen-4-ylidene)malononitrile, respectively, with the participation of [1-(2-n-butoxyethyl)-2,2,4,7-tetramethyl-1,2,3,4-tetrahydroquinolin-6-yl)]-carbaldehyde. First hyperpolarizability (β) was calculated for the obtained compounds using the M05-2X functional and 6-31+G (d) basis. Optical properties and solvatochromism in solvents of different polarity (toluene, 1,4-dioxane, chlorobenzene, dichloromethane, DMF, and ethanol) were also investigated.

The dynamic behaviour of a porphyrin dimer, based on the covalent linkage of two macrocyclic moieties with a butadiyne connector, was studied in thin films by UV-Vis and emission spectroscopies. The degree of π-conjugation through control of intramolecular motion was investigated without employing extreme conditions such as cryogenic temperatures or high viscosity. By exploiting the propensity of the dimer to bind axial ligands through Zn–N bonds, it was shown that the co-planar and orthogonal conformations of the dimer may be stabilized in ultrathin films at the air/water interface. Furthermore, using the Langmuir–Blodgett technique, monolayer-thick matrix-free films on solid substrates containing the porphyrin dimer were obtained. In the latter case, the dimer exists in either an exclusively co-planar state or a mixture of conformational states depending on the nature of the axial ligand: 1,4-diazabicyclo[2.2.2]-octane (DABCO) or 4-aminomethylpyridine (AMP).

International audience; Reusable dual-channel optical sensors for Hg2+ ions were prepared by Langmuir-Schaefer (LS) method from amphiphilic (trans-A2)BC-type porphyrins functionalized at meso-positions of the tetrapyrrolic macrocycle by sterically demanding diethoxyphosphoryl and mesityl groups as well as electron donating RO, RS or RNH substituents (R = n-C8H17). These three novel amphiphilic porphyrin derivatives were synthesized in good yields and their floating films at the air⎯water interface were investigated. In these monolayers, porphyrin molecules display a slipped stack-of-card orientation, but their strong π stacking is prohibited by bulky diethoxyphosphoryl and mesityl groups. The heteroatom substituent plays a key role in the molecular organization of the monolayers because it can participate in intermolecular hydrogen bonding, which influences the monolayer structure. Sensing properties of the porphyrins organized in Langmuir monolayers differ from those in the solution environment. Selective spectrophotometric detection of Hg2+ ions by these floating films is observed because interfering Cu2+, Zn2+, Cd2+, and Pb2+ ions are coordinated to donor centers located at the periphery of the macrocycle. Transfer of these floating films onto a polyvinyl chloride surface by LS technique affords perforated multilayer films with a tight molecular coverage of the solid support. The effect of the heteroatoms on the organization of these films was demonstrated by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Both absorption and emission studies provide a strong evidence that chromophore-chromophore interactions are rather weak in these LS films. Binding of mercury(II) ions by the films and the regeneration of the sensors were explored visually and using reflection absorbance and fluorescence spectroscopies and then confirmed by X-ray fluorescence analysis. Detection limit of these selective and reusable dual-channel (absorbance and fluorescence) thin-film sensors is about 10-8 M (2 ppb), that corresponds to the action level for Hg2+ ions in drinking water recommended by the U.S. Environmental Protection Agency (EPA).

Cellular membrane is one of the main targets of photodynamic therapy. Its high complexity has led to the study of the efficiency of photosensitizers on artificial lipid systems mimicking membranes. However, the preliminary analysis of this efficiency remains limited due to difficulty of the model construction and/or implementation of the required measurement techniques. Hereby, we propose a quite simple way for the rapid comparative assessment of novel photosensitizers in terms of membrane photodegradation, based on simple and fast measurements, such as wetting angle and surface plasmon resonance spectroscopy. As a proof of concept, we applied this methodology to two bacteriopurpurinimide derivatives. We have shown in particular that such complementary techniques can be employed not only for the multiparametric monitoring of the kinetics of the photodegradation, but also for the comparison of the damaging efficiency of the photosensitizers in the lipid structures as well.

Europium(III) and terbium(III) complexes with 4-n-octyloxybenzoic acid of the composition LnL3 were synthesized and their luminescent properties were studied. It was established that the luminescence intensity of the TbL3 complex in the visible region is much higher than that of EuL3. Langmuir monolayers of these compounds on the water subphase and Langmuir–Blodgett films on solid substrates were prepared. The morphological characteristics of the latter were studied. The results obtained indicate good prospects for application of these compounds in the design and fabrication of planar photonic and optoelectronic devices.

The efficiency of the Forster resonance energy transfer (FRET) in a monolayer film containing the energy donor and energy acceptor fluorophores is low since the energy transfer process occurs in one plane only. As the number of layers increases to five, the energy transfer efficiency increases due to the interlayer energy transfer occurring in three dimensions. Further increase in the number of layers (up to 10) causes no significant increase in the efficiency since in this case the total film thickness exceeds an optimum value for the FRET process.

The results of a study of the photochromic properties of 1´-hexadecyl-3´,3´-dimethyl-6-nitro-1´,3´-dihydrospiro[chromene-2,2´-indole] (SP) are presented. The kinetic characteristics of photophysical processes occurring in acetonitrile solution of SP upon irradiation with UV light and during dark relaxation are determined. It is shown that spiropyran modified at the nitrogen atom by a long-chain hydrocarbon radical exhibits photochromic properties in the dissolved state, with the rate of the direct photocoloration exceeding the rate of dark relaxation by an order of magnitude. Comparative studies of SP photoreaction in dissolved and 2D states are carried out. The obtained results open up broad prospects for application of such photochromes in thin-film devices obtained using the Langmuir monolayer technique.

Cambrian Lagerstätten host rocks are frequently composed of kaolinite and chlorite in varying amounts; accordingly, our goal was to study the preservation potential of crustaceans in these two clays. We conducted long-term experiments (12–18 months, the longest duration of actualistic taphonomy experiments from published literature) on the decay of Artemia salina in these clay sediments. The degree of preservation, transformed mineralogical composition of the sediments, and the elemental composition of the nauplial remains were examined. We demonstrate that the kaolinite and chlorite sediment enhanced the preservation (in the kaolinite the effect was considerably higher than in the chlorite) compared with the sediment-free control. pH inside the sediments dropped to 6.5–7.1 and was even lower (

This study takes a novel approach to the enhancement of receptor properties of thin-film sensors based on hemicyanine dyes with dithia-aza-crown-ionophoric moiety. By means of in situ UV-vis and X-ray reflectivity (XRR) measurements, it was revealed that the introduction of up to 0.25 mmol of Hg2+ under a preliminarily compressed monolayer, formed on pure water, does not lead to cation binding. This is due to the formation of "head-to-tail" aggregates (H-type), in which ionophoric group is blocked by the neighboring molecule. However, the presence of barium cations in the subphase under the forming Langmuir monolayer of the mentioned compound causes codirectional (head-to-head) orientation of chromoionophore fragments. This provides preorganization of a monolayer structure that facilitates the binding of complementary mercury cations, even in a compressed state: asymmetric sandwich complexes containing two dye molecules coordinate a Hg2+ cation between them. This complex structure was confirmed by molecular modeling based on the electron density distribution calculated from XRR measurement data. Such preorganization of supramolecular ensembles induced by cations, which do not participate in the complex formation with macroheterocyclic receptors, may have applications in fields where strict control of molecular orientation at the interface is required, such as nanoelectronics, sensorics, catalysis, etc.

One of the priority problems in the development and use of databases is that of information security. It becomes substantially more complicated when databases are implemented in cloud computing systems. In our previous paper we studied this problem for the simple case of databases with one-bit records; we offered a criterion of deductive security for queries to such databases, proved the hardness of its checking, and showed that for some classes of queries deductive security can be verified relatively easy. In this paper these results are generalized for the case of more complex databases with multi-bit records.

An ultrathin film, wherein a resonance energy transfer (FRET) from the energy donor monolayer to the analyte sensitive acceptor monolayer is controlled by definable cation binding, was produced, thus proving the feasible concept of non-covalently linked FRET couple based sensors.

We study certain simple models of confidential databases in cloud computing systems. In the framework of these models we introduce a concept of deductive security for queries to such databases, find necessary and sufficient conditions of deductive security, and describe some classes of queries which satisfy these requirements.

Macrocyclic tetrapyrrolic compounds, such as naturally occurring or artificial porphyrins and phthalocyanines, have unique and highly attractive properties for applications in medicine and technology. The interaction of free-base phthalocyanine (H2Pc) and tetraphenylporphyrin (H2TPP) molecules with low-energy (0-15 eV) electrons was studied in vacuo by means of negative ion resonant electron capture mass spectrometry. Close similarities in formation and decay of negative ions of these compounds were revealed. Efficient formation of long-lived molecular negative ions (MNIs) was observed in the incident electron energy range of 0-8 eV, unprecedentedly wide for organic compounds and comparable to the range characteristic to carbon atomic clusters, fullerenes. Experiments testify to the strong persistence of MNIs of both compounds to dissociative decay, isomerization, and electron autodetachment. Lifetimes of MNIs as a function of incident electron energy were measured and it was concluded that the isolated anions may retain additional electrons in a time scale of up to hundreds of seconds at standard temperature due to the high adiabatic electron affinity of these large molecules. For the representatives of dyes and photochromic compounds comprehensively studied in terms of interaction with light, the present work highlights yet another unique property of these molecules, namely the capability to attach and durably retain an additional electron of low, pre-ionization energy.

Herein we report the synthesis and characterization of a series of new dyads – imidazo-fused Ni(II) porphyrinates, containing polycyclic aromatic hydrocarbons (PAH) at the C-2 position of the imidazole ring, including pyrene – 1Pyr, anthracene – 1An, and diphenylanthracene – 1Ph2An. Electronic communication between the tetrapyrrolic macrocycles and PAH moieties was comprehensively studied by UV–Vis and fluorescence spectra together with quantum-chemical modelling. DFT calculations, including geometry optimization and analysis of the frontier orbitals, has revealed the efficient conjugation of pyrene and anthracene with porphyrin π-system, while 1Ph2An dyad possessed two isolated non-conjugated π-systems. Interestingly, these conclusions could not be unambiguously ruled out of UV–Vis spectroscopy data alone. Finally, the presence or absence of conjugation was confirmed using the analysis of ellipticities of bond critical points, thus proving this method to be a convenient tool to study the conjugation in multichromophoric porphyrin-based systems.

Lagerstatten, places where soft-bodied organisms became mineralized, provide a substantial bulk of palaeobiological information, but the detailed mechanisms of how soft-tissue preservation takes place remain debatable. An experimental taphonomy approach, which allows for direct study of decay and mineralization, offers a means to study the preservational potential of different soft-bodied organisms under controlled conditions. Here we compare the preservational capacity of two types of clay (kaolinite and montmorillonite) through a long-term (24 month) experiment involving the burial and decay of small crustaceans. Our experimental design is innovative in that it models catastrophic sedimentation in fine-grained colloidal suspension, which is believed to form Lagerstatten deposits. We demonstrated better preservation of buried organisms in clays compared to water, and in kaolinite compared to montmorillonite. As aluminium cations were present in high concentrations in kaolinite sediment but not in montmorillonite, the better preservation in kaolinite is attributed to the tanning properties of aluminium, which catalyses cross-linking in proteins, protecting them from bacterial degradation. Anaerobic environments and acidification also slow down decay, but they are less effective than tanning. Kaolinite and montmorillonite replaced the crustacean integuments differently: in the remains buried in kaolinite, Al and Si were detected in equal proportions, while in those buried in montmorillonite, the Si content appeared to be much higher even in comparison with the initial sample of the clay. These variations probably arose from the different dynamics of acidic hydrolysis in the two clays associated with anaerobic decomposition of organic matter. Our results show that the preservation mechanism includes multi-component interactions between the solution, mineral, sediment and organic remains; taken separately, any single component explains little. The specific conditions that occur within the colloidal clay sediments can facilitate conservation and start fast mineralization according to chemical properties and elemental content.

The mechanism that guides the formation of exceptionally preserved fossils with soft tissues variously displayed is a paramount challenge to paleontology. The key question for exceptional preservation is the nature of the slowdown of decay and acceleration of soft tissue mineralization. Here we report the experimental formation of subfossils of the brine shrimp Artemia salina (Crustacea, Branchiopoda), which were produced during 14 months of aging in a kaolinite clay sediment. EDS/SEM elemental analyses showed that the subfossils were preserved as thin clay-organic replicas that displayed fine anatomical details. Decomposition in the clay-colloidal solution established highly heterogeneous acidic conditions, with the lowest pH typically found in the vicinity of the buried organisms, and visually manifested in patchy coloration of the sediment. Elevated acidity is likely what ultimately slowed the decay. An acidic environment increases the rate of clay destruction and, consequently, the diffusion rate decline. As a result, the acidic products quickly accumulate around a buried body; this in turn inhibits bacterial proliferation, accelerates the acidic hydrolysis of clay and, accordingly, the release of tanning and mineralizing agents. The subfossils remained stable under experimental high pressure and temperature. These model subfossils exhibit features that are typical of some Lagerstätten fossils preserved in fine-grained sediments.

We study a formal model of cloud computing systems with auxiliary cryptoservers. Assuming an existence of a secure threshold somewhat homomorphic public key cryptosystem we show how to build a cloud computing system secure in this model.

Di- n -octylated tetranitrothiacalix[4]arene, a new multidipolar D-π-A chromophore has been synthesized and the dependence of its aggregation in solution and at the air–water interface on the concentration of solution and spreading solvent has been evaluated.