Extra Density Research Articles

Role of the Diamagnetic Zinc(II) Ion in Determining the Electronic Structure of Lanthanide Single-Ion Magnets.

Four complexes containing DyIII and PrIII ions and their LnIII -ZnII analogs have been synthesized in order to study the influence that a diamagnetic ZnII ion has on the electronic structure and hence, the magnetic properties of the DyIII and PrIII single ions. Single-crystal X-ray diffraction revealed the molecular structures as [DyIII (HL)2 (NO3 )3 ] (1), [PrIII (HL)2 (NO3 )3 ] (2), [ZnII DyIII (L)2 (CH3 CO2 )(NO3 )2 ] (3) and [ZnII2 PrIII (L)2 (CH3 CO2 )4 (NO3 )] (4) (where HL=2-methoxy-6-[(E)-phenyliminomethyl]phenol). The dc and ac magnetic data were collected for all four complexes. Compounds 1 and 3 display frequency dependent out-of-phase susceptibility signals (χM "), which is a characteristic signature for a single-molecule magnet (SMM). Although 1 and 3 are chemically similar, a fivefold increase in the anisotropic barrier (Ueff ) is observed experimentally for 3 (83 cm-1 ), compared to 1 (16 cm-1 ). To rationalize the larger anisotropic barrier (1 vs. 3), detailed ab initio calculations were performed. Although the ground state Kramer's doublet in both 1 and 3 are axial in nature (gzz =19.443 for 1 and 18.82 for 3), a significant difference in the energy gap (Ueff ) between the ground and first excited Kramer's doublet is calculated. This energy gap is governed by the electrostatic repulsion between the DyIII ion and the additional charge density found for the phenoxo bridging ligand in 3. This extra charge density was found to be a consequence of the presence of the diamagnetic ZnII ion present in the complex. To explore the influence of diamagnetic ions on the magnetic properties further, previously reported and structurally related Zn-DyIII complexes were analyzed. These structurally analogous complexes unambiguously suggest that the electrostatic repulsion is found to be maximal when the Zn-O-Dy-O dihedral angle is small, which is an ideal condition to maximize the anisotropic barrier in DyIII complexes.

Investigation of intrinsic defect magnetic properties in wurtzite ZnO materials

Theoretical and experimental investigations of the ferromagnetism induced by intrinsic defects inside wurtzite zinc oxide structures are performed using magnetic field-dependent circular dichroism (MCD-H), direct magnetization measurement (M-H) by superconducting quantum interference device (SQUID) as well as by generalized gradient density functional theory (GGA-DFT). To investigate localized magnetic moments of bulk material intrinsic defects - vacancies, interstitial atoms and Frenkel defects, various-size periodic supercells are calculated. It is shown that oxygen interstitial atoms (Oi) or zinc vacancies (Znv) generate magnetic moments of 1,98 и 1,26µB respectively, however, the magnitudes are significantly reduced when the distance between defects increases. At the same time, the magnetic moments of oxygen Frenkel defects are large (~1.5–1.8µB) and do not depend on the distance between the defects. It is shown that the origin of the induced ferromagnetism in bulk ZnO is the extra spin density on the oxygen atoms nearest to the defect. Also dependence of the magnetization of ZnO (101̅0)and(0001) thin films on the positions of Oi and Znv in subsurface layers were investigated and it is shown that the magnetic moments of both defects are significantly different from the values inside bulk material. In order to check theoretical results regarding the defect induced ferromagnetism in ZnO, two thin films doped by carbon (C) and having Zn interstitials and oxygen vacancies were prepared and annealed in vacuum and air, respectively. According to the MCD-H and M-H measurements, the film, which was annealed in air, exhibits a ferromagnetic behavior, while the other does not. One can assume annealing of ZnO in vacuum should create oxygen vacancies or Zn interstitial atoms. At that annealing of the second C:ZnO film in air leads to essential magnetization, probably by annihilation of oxygen vacancies, formation of interstitial oxygen atoms or zinc vacancies. Thus, our experimental results confirm our theoretical conclusions that ZnO magnetization origin are Oi or Znv defects.

Efficient ion acceleration by relativistic self-induced transparency in subwavelength targets

In this work we have studied the effect of target thickness on relativistic self-induced transparency (RSIT) and found out that for subwavelength targets the corresponding threshold target density (beyond which target is opaque to incident laser pulse of a given intensity) increases. The accelerating longitudinal electrostatic field created by RSIT from subwavelength target is used to accelerate the ion bunch from a thin, low density layer behind the main target to $\sim$ 100 MeV. A suitable scaling law for optimum laser and target conditions is also deduced. The word `via' in the title signifies the fact that we are interested in acceleration of ions from the layer placed behind the target. It is also being observed that as per as energy spectrum is concerned; an extra low density layer is advantageous than relying on target ions alone.

Merging Single-Atom-Dispersed Silver and Carbon Nitride to a Joint Electronic System via Copolymerization with Silver Tricyanomethanide.

Herein, we present an approach to create a hybrid between single-atom-dispersed silver and a carbon nitride polymer. Silver tricyanomethanide (AgTCM) is used as a reactive comonomer during templated carbon nitride synthesis to introduce both negative charges and silver atoms/ions to the system. The successful introduction of the extra electron density under the formation of a delocalized joint electronic system is proven by photoluminescence measurements, X-ray photoelectron spectroscopy investigations, and measurements of surface ζ-potential. At the same time, the principal structure of the carbon nitride network is not disturbed, as shown by solid-state nuclear magnetic resonance spectroscopy and electrochemical impedance spectroscopy analysis. The synthesis also results in an improvement of the visible light absorption and the development of higher surface area in the final products. The atom-dispersed AgTCM-doped carbon nitride shows an enhanced performance in the selective hydrogenation of alkynes in comparison with the performance of other conventional Ag-based materials prepared by spray deposition and impregnation-reduction methods, here exemplified with 1-hexyne.

If Gel and Mass Spec Don't Help, Use cryo-EM to Characterise your Specimen

Cryo-EM has proven to be efficient in obtaining high-res maps for purified and well-characterized specimen. But how about heterogenous complexes with unknown associated moieties?We applied cryo-EM to the pool of free ribosomal subunits in human mitochondria. Intensive classification generated 3.5 A resolution map from 60% of the total particles. Comparison of the map with that of the intact human mitoribosome revealed disordered rRNA at the interface and presence of a silencing factor. This suggested that the subset of particles isolated directly from the cellular compartment represents mitoribosome assembly intermediate.Further inspection revealed extra protein density of an unknown origin bound to the silencing factor, namely ‘silencing factor binding protein’. The model clearly suggests a function for this newly discovered protein in mitoribosome biogenesis. Therefore we present first high-res model of mitoribosome assembly intermediate and show that cryo-EM can be used to identify new proteins, propose their function and provide a basis for designing new biochemical experiments to further investigate the discovered mechanisms.

Improved Electrochemical Performance of a ZnFe2O4 Nanoflake‐Based Supercapacitor Electrode by Using Thiocyanate‐Functionalized Ionic Liquid Electrolytes

AbstractThiocyanate‐functionalized ionic liquids (ILs) 1‐butyl‐3‐methylimidazolium thiocyanate [BMIM][SCN], 1‐ethyl‐3‐methylimidazolium thiocyanate [EMIM][SCN], and 3‐methylimidazolium thiocyanate [MIM][SCN], with varying chain lengths, were synthesized by using metathesis followed by ion exchange under reflux conditions. These ILs were investigated for their application as electrolyte with a ZnFe2O4 nanoflake‐based supercapacitor electrode; they exhibited significantly better performance than any other previously reported ILs used as electrolytes. [BMIM][SCN] showed higher specific capacitance (781 F g–1), cycle stability (95 % retention, 3000 cycle), and energy density (156 W h kg–1) than [EMIM][SCN] (590 F g–1, 86 % retention, and 78 W h kg–1) and [MIM][SCN] (250 F g–1, 80 % retention, and 50 W h kg–1). The ZnFe2O4 nanoflake electrodes were able to deliver an energy density of 156 W h kg–1 even at an extra high power density of 7.11 kW kg–1 in [BMIM][SCN] electrolyte, justifying its utility as a potential electrolyte. Furthermore, the effect of how the hydrated ions of the ILs in aqueous media influence the overall performance of the supercapacitor was studied systematically and found to be contrary to the reported trend and use of pure ILs as electrolytes.

Subdominant Dark Matter sterile neutrino resonant production in the light of PLANCK

Few independent detections of a weak X-ray line at an energy of ∼ 3.5 keV seen toward a number of astrophysical sites have been reported. If this signal will be confirmed to be the signature of decaying DM sterile neutrino with a mass of ∼ 7.1 keV, then the cosmological observables should be consistent with its properties.In this paper we make a coupled treatment of the weak decoupling, primordial nucleosynthesis and photon decoupling epochs in the sterile neutrino resonant production scenario, including the extra radiation energy density via Neff. We compute the radiation and matter perturbations including the full resonance sweep solution for να/ν̄α → νs flavor conversion in the expanding Universe.We show that the cosmological measurements are in agreement with subdominant Dark Matter sterile neutrino resonant production with following parameters (errors at 95% CL): mass mνs=6.08 ± 3.22 keV, mixing angle sin2 2θ < 5.61 × 10−10, lepton number per flavor L4 = 1.23 ± 0.04 (L4 ≡ 104 Lνa) and sterile neutrino mass fraction fνs< 0.078.Our results are in good agreement with the sterile neutrino resonant production parameters inferred in ref. [1] from the linear large scale structure constraints to produce full Dark Matter density.

Improving the Lifetime and Cycle Life of NMC/Graphite Li-Ion Cells Charged to 4.4 or 4.5V

Significant extra capacity and energy density can be obtained from NMC/graphite cells by increasing the upper voltage cutoff from 4.2V to 4.5V. However, when this is done, parasitic reactions between the charged NMC electrodes and the electrolytes accelerate and cell lifetime is compromised. In this lecture, I will review recent work in our laboratory that has focussed on increasing the lifetime of NMC/graphite Li-ion cells charged to 4.4 or 4.4V. This work has centered around: 1) Quantifying parasitic reactions using Ultra High Precision Coulometry, Isothermal Battery Microcalorimetry and Automated Cycling/Impedance Spectroscopy measurements; 2) Reducing the rate of parasitic reactions through the use of electrolyte additives; and 3) Using surface science techniques, e.g. XPS, to understand how these electrolyte additives function. The results of this work are NMC622/graphite, NMC532/graphite, NMC422/graphite and NMC111/graphite cells which have improved properties for high voltage use. This work has been carried out by a large number of graduate students and post doctoral fellows including Dr. Mengyun Nie, Dr. Jian Xia, Dr. Lenaic Madec, Dr. David Hall, Dr. David Yaohui Wang, Lin Ma, Kathlyne Nelson, Laura Downie, Remi Petibon, Julian Self, Leah Ellis, Deijun Xiong and Chris Burns. Collaborations with researchers at 3M Company, including Dr. Ang Xiao, Dr. Bill Lamanna and Dr. Kiah Smith have been vital for this work. The authors acknowledge Dr. Jing Li of BASF for supply of many of the electrolyte solvents and additives used in these studies. Dr. Yong-Shou Lin and Dr. David Wang of ATL Battery Co. are acknowledged for the supply of some of the dry pouch cells used in these studies. The authors thank the Natural Sciences and Engineering Research Council of Canada and 3M Canada Company for funding of this work.

Extending Feistel structure to DNA Cryptography

DNA cryptography is a novel field being taken up by the researcher community for research now days in order to have secure communication on a network. This technique is inspired from biological science, in which DNA is used as an information carrier from one generation to another. DNA cryptography is proposed for a secure end to end communication due to the vast parallelism and extra ordinary information density that are inherent in any DNA molecule. In this paper previous algorithm based on DNA cryptography is enhanced in terms of its security parameter by incurring feistel inspired structure in it. This adds some sort of confusion and diffusion, which makes it complex enough that it restricts the adversary to perform any kind of brute force attack. Encryption and decryption time is also compared on the basis of variable plaintext size.

Reionization constraints on primordial magnetic fields

We study the impact of the extra density fluctuations induced by primordial magnetic fields on the reionization history in the redshift range: $6 < z < 10$. We perform a comprehensive MCMC physical analysis allowing the variation of parameters related to primordial magnetic fields (strength, $B_0$, and power-spectrum index $n_{\scriptscriptstyle \rm B}$), reionization, and $\Lambda$CDM cosmological model. We find that magnetic field strengths in the range: $B_0 \simeq 0.05{-}0.3$ nG (for nearly scale-free power spectra) can significantly alter the reionization history in the above redshift range and can relieve the tension between the WMAP and quasar absorption spectra data. Our analysis puts upper-limits on the magnetic field strength $B_0 < 0.358, 0.120, 0.059$ nG (95 % c.l.) for $n_{\scriptscriptstyle \rm B} = -2.95, -2.9, -2.85$, respectively. These represent the strongest magnetic field constraints among those available from other cosmological observables.

Structural analysis of PseH, the Campylobacter jejuni N-acetyltransferase involved in bacterial O-linked glycosylation

Campylobacter jejuni is a bacterium that uses flagella for motility and causes worldwide acute gastroenteritis in humans. The C. jejuni N-acetyltransferase PseH (cjPseH) is responsible for the third step in flagellin O-linked glycosylation and plays a key role in flagellar formation and motility. cjPseH transfers an acetyl group from an acetyl donor, acetyl coenzyme A (AcCoA), to the amino group of UDP-4-amino-4,6-dideoxy-N-acetyl-β-l-altrosamine to produce UDP-2,4-diacetamido-2,4,6-trideoxy-β-l-altropyranose. To elucidate the catalytic mechanism of cjPseH, crystal structures of cjPseH alone and in complex with AcCoA were determined at 1.95 Å resolution. cjPseH folds into a single-domain structure of a central β-sheet decorated by four α-helices with two continuously connected grooves. A deep groove (groove-A) accommodates the AcCoA molecule. Interestingly, the acetyl end of AcCoA points toward an open space in a neighboring shallow groove (groove-S), which is occupied by extra electron density that potentially serves as a pseudosubstrate, suggesting that the groove-S may provide a substrate-binding site. Structure-based comparative analysis suggests that cjPseH utilizes a unique catalytic mechanism of acetylation that has not been observed in other glycosylation-associated acetyltransferases. Thus, our studies on cjPseH will provide valuable information for the design of new antibiotics to treat C. jejuni-induced gastroenteritis.

The large tegument protein pUL36 is essential for formation of the capsid vertex-specific component at the capsid-tegument interface of herpes simplex virus 1.

ABSTRACTHerpesviruses have a characteristic particle structure comprising an icosahedral capsid, which contains the DNA genome and is, in turn, surrounded by a proteinaceous tegument layer and a lipid envelope. In herpes simplex virus, the interaction between the capsid and tegument is limited to the capsid vertices and involves two minor capsid proteins, pUL17 and pUL25, and the large inner tegument protein pUL36. pUL17 and pUL25 form a heterodimeric structure, the capsid vertex-specific component (CVSC), that lies on top of the peripentonal triplexes, while pUL36 has been reported to connect the CVSC to the penton. In this study, we used virus mutants with deletions in the genes for pUL36 and another inner tegument protein, pUL37, to analyze the contributions of these proteins to CVSC structure. Using electron cryomicroscopy and icosahedral reconstruction of mutants that express pUL17 and pUL25 but not pUL36, we showed that in contrast to accepted models, the CVSC is not formed from pUL17 and pUL25 on their own but requires a contribution from pUL36. In addition, the presence of full-length pUL36 results in weak density that extends the CVSC toward the penton, suggesting either that this extra density is formed directly by pUL36 or that pUL36 stabilizes other components of the vertex-tegument interface. IMPORTANCE Herpesviruses have complex particles that are formed as a result of a carefully controlled sequence of assembly steps. The nature of the interaction between two of the major particle compartments, the icosahedral capsid and the amorphous tegument, has been extensively studied, but the identity of the interacting proteins and their roles in forming the connections are still unclear. In this study, we used electron microscopy and three-dimensional reconstruction to analyze virus particles formed by mutants that do not express particular interacting proteins. We show that the largest viral protein, pUL36, which occupies the layer of tegument closest to the capsid, is essential for formation of structurally normal connections to the capsid. This demonstrates the importance of pUL36 in the initial stages of tegument addition and provides new insights into the process of virus particle assembly.

Examination of the ambient effects on the stability of amorphous indium-gallium-zinc oxide thin film transistors using a laser-glass-sealing technology

The effect of an ambient atmosphere with a positive bias constant current stress (CCS) and a negative bias illumination stress (NBIS) on the stability of amorphous In-Ga-Zn-O thin film transistors (TFTs) is examined by utilizing a glass-hermetic-sealant with a moisture permeability of less than 10−6 g/m2 · day. In the CCS test, the threshold voltage shift (ΔVth) was remarkably suppressed in the glass-sealed TFTs. The unsealed and resin-sealed TFTs exhibited large ΔVth values. During the NBIS tests, the glass-sealed TFTs had almost the same negative ΔVth as the unsealed and resin sealed TFTs. Among the different TFTs, no significant differences were observed in the threshold voltage, the subthreshold swing and the saturation mobility as a function of the photon energy. It is concluded that ambient molecules were the primary origin of the instability of the ΔVth, induced by a CCS, but they were not related to the NBIS instability. The major role of the effective passivation layers in the NBIS test was not to simply block out the ambient effects, but to reduce the extra density of states at/near the surface of the back channel.

Late-time vacuum phase transitions: Connecting sub-eV scale physics with cosmological structure formation

We show that a particular class of postrecombination phase transitions in the vacuum can lead to localized overdense regions on relatively small scales, roughly 10^6 to 10^10 M_sun, potentially interesting for the origin of large black hole seeds and for dwarf galaxy evolution. Our study suggests that this mechanism could operate over a range of conditions which are consistent with current cosmological and laboratory bounds. One byproduct of phase transition bubble-wall decay may be extra radiation energy density. This could provide an avenue for constraint, but it could also help reconcile the discordant values of the present Hubble parameter (H_0) and sigma_8 obtained by cosmic microwave background (CMB) fits and direct observational estimates. We also suggest ways in which future probes, including CMB considerations (e.g., early dark energy limits), 21-cm observations, and gravitational radiation limits, could provide more stringent constraints on this mechanism and the sub-eV scale beyond-standard-model physics, perhaps in the neutrino sector, on which it could be based. Late phase transitions associated with sterile neutrino mass and mixing may provide a way to reconcile cosmological limits and laboratory data, should a future disagreement arise.

Different responses of arbuscular mycorrhizal fungal community to day-time and night-time warming in a semiarid steppe

Arbuscular mycorrhizal (AM) fungi form mutualistic symbioses with most plant species and play important roles in ecosystems. Knowledge of the response of AM fungi to temperature change will improve our understanding of the function of AM fungal community under global climate change scenarios in ecosystems. The effects of constant warming on AM fungal communities have been investigated previously, but responses to asymmetrical warming over 24-h periods have never been documented in natural ecosystems. In this study, we examined AM fungal communities in a full factorial design including day-time and night-time warming in a semiarid steppe in northern China. Day-time and 24-h warming, but not night-time warming, significantly increased AM fungal spore density. In contrast, none of the three warming regimes had a significant effect on AM fungal extra radical hyphal density. A total of 161 operational taxonomic units (OTUs) of AM fungi were recovered by 454 pyrosequencing of 18S rDNA. Day-time, night-time, and 24-h warming all significantly increased AM fungal OTU richness. Some AM fungal OTUs showed a significant bias toward day-time, night-time or 24-h warming. The AM fungal community composition was significantly affected by night-time warming, but not by day-time and 24-h warming. Our finding highlighted different responses of AM fungal spore density and community composition to asymmetrical warming. This study might improve our understanding of ecosystem functioning of AM fungal community under global climate change scenarios in a semiarid steppe ecosystem.

Effect by Doping and Surface Termination on c-BN Surface Reactivity: A Theoretical DFT Approach

The cubic phase of boron nitride, c-BN, is a very promising material due to its very interesting and extreme properties, of which some are comparable or even superior to diamond. However, there are severe problems with the initial nucleation during vapor phase synthesis of c-BN thin films. Investigations of new possibilities for growth mechanisms are therefore of greatest importance to perform. It has experimentally been shown that the film quality will increase when a small amount of oxygen is added into the film during deposition. In the present study, the adsorption and abstraction energies of the surface terminating species, the geometrical structures, and the resulting electronic structures were studied for the situation when N (or B) was substituted by O (or C) atom in combination with different terminating species (H, F, or Cl) on the c-BN (100) surface. This theoretical study was performed by using first-principles functional theory (DFT) calculations under periodic boundary conditions. The results indicate that the reactivity of the B-rich c-BN (100)-2 × 1 surface is more pronounced when doping an H-terminated surface with O (or C). For a corresponding F-terminated surface, only the C-doped surface will result in a more exothermic adsorption process. Doping with O gives a slightly less exothermic adsorption process, when compared to the nondoped situation. The situation was completely different for the N-rich c-BN (100)-1 × 1 surface, where the H and F terminating species were found to chemisorb stronger for the nondoped situation than for the O (or C)-doped one. When Cl-terminating the surfaces, all the adsorption processes became endothermic and hence not possible to perform. The results from the DFT calculations also indicate that the extra electron density induced in the system by doping with O or C atoms will not stay in the nearest vicinity to the respective dopant, but will instead move closer to the nearest surface atoms. This overall increase in electron density was observed to either strengthen the surface-terminating bonds for the B-rich surface or weaken these bonds for the N-rich surface. The reactivity of the terminated surfaces, as obtained from the Fukui functions, revealed a much larger variation in electrophilic and nucleophilic susceptibility for the doped N-rich surfaces, as compared with the doped B-rich ones.

Human Full-Length Coagulation Factor X and a GLA Domain-Derived 40-mer Polypeptide Bind to Different Regions of the Adenovirus Serotype 5 Hexon Capsomer

The interaction of human adenovirus (HAdV)-C5 and many other adenoviruses with blood coagulation factors (e.g., human factor X, FX) involves the binding of their GLA domain to the hexon capsomers, resulting in high levels of hepatotropism and potential hepatotoxicity. In this study, we tested the possibility of preventing these undesirable effects by using a GLA-mimicking peptide as a competitor. An FX GLA domain-derived, 40-mer polypeptide carrying 12 carboxyglutamate residues was synthesized (GLA(mim)). Surface plasmon resistance (SPR) analysis showed that GLA(mim) reacted with free and capsid-embedded hexon with a nanomolar affinity. Unexpectedly, GLA(mim) failed to compete with FX for hexon binding, and instead significantly increased the formation of FX-hexon or FX-adenovirion complexes. This observation was confirmed by in vitro cell transduction experiments using HAdV-C5-Luciferase vector (HAdV5-Luc), as preincubation of HAdV5-Luc with GLA(mim) before FX addition resulted in a higher transgene expression compared with FX alone. HAdV-C5 virions complexed with GLA(mim) were analyzed by cryoelectron microscopy. Image reconstruction demonstrated the bona fide hexon-GLA(mim) interaction, as for the full-length FX, although with considerable differences in stoichiometry and relative location on the hexon capsomer. Three extra densities were found at the periphery of each hexon, whereas one single FX molecule occupied the central cavity of the hexon trimeric capsomer. A refined analysis indicated that each extra density is found at the expected location of one highly variable loop 1 of the hexon, involved in scavenger receptor recognition. HAdV5-Luc complexed with a bifunctional GLA(mim)RGD peptide showed a lesser hepatotropism, compared with control HAdV5-Luc alone, and efficiently targeted αβ-integrin-overexpressing tumor cells in an in vivo mouse tumor model. Collectively, our findings open new perspectives in the design of adenoviral vectors for biotherapy.

State of the blood lipid profile in acute period of recurrent ischemic stroke

In patients with both primary and recurrent ischemic stroke in its acute period the combined dyslipidemia with no probable differences was found which declared itself in an increase of general cholesterol, cholesterol of low den sity lipoproteins, cholesterol of extra low density lipoproteins, triglycerides and atherogenic factor at low concentrations of cholesterol of high density lipoproteins. There were no significant differences found between the indexes of lipidogram of different levels of severity in the primary ischemic stroke group as well as in the group of recurrent ischemic stroke, and no significant differences betweentheir same name levels of severity were found either.

Clusterized nuclear matter in the (proto-)neutron star crust and the symmetry energy

Though generally agreed that the symmetry energy plays a dramatic role in determining the structure of neutron stars and the evolution of core-collapsing supernovae, little is known in what concerns its value away from normal nuclear matter density and, even more important, the correct definition of this quantity in the case of unhomogeneous matter. Indeed, nuclear matter traditionally addressed by mean-field models is uniform while clusters are known to exist in the dilute baryonic matter which constitutes the main component of compact objects outer shells. In the present work we investigate the meaning of symmetry energy in the case of clusterized systems and the sensitivity of the proto-neutron star composition and equation of state to the effective interaction. To this aim an improved Nuclear Statistical Equilibrium (NSE) model is developed, where the same effective interaction is consistently used to determine the clusters and unbound particles energy functionals in the self-consistent mean-field approximation. In the same framework, in-medium modifications to the cluster energies due to the presence of the nuclear gas are evaluated. We show that the excluded volume effect does not exhaust the in-medium effects and an extra isospin and density dependent energy shift has to be considered to consistently determine the composition of subsaturation stellar matter. The symmetry energy of diluted matter is seen to depend on the isovector properties of the effective interaction, but its behavior with density and its quantitative value are strongly modified by clusterization.

Chemically functionalized carbon films for single molecule imaging

Many biological complexes are naturally low in abundance and pose a significant challenge to their structural and functional studies. Here we describe a new method that utilizes strong oxidation and chemical linkage to introduce a high density of bioactive ligands onto nanometer-thick carbon films and enable selective enrichment of individual macromolecular complexes at subnanogram levels. The introduced ligands are physically separated. Ni-NTA, Protein G and DNA/RNA oligonucleotides were covalently linked to the carbon surface. They embody negligible mass and their stability makes the functionalized films able to survive long-term storage and tolerate variations in pH, temperature, salts, detergents, and solvents. We demonstrated the application of the new method to the electron microscopic imaging of the substrate-bound C3PO, an RNA-processing enzyme important for the RNA interference pathway. On the ssRNA-linked carbon surface, the formation of C3PO oligomers at subnanomolar concentrations likely mimics their assembly onto ssRNA substrates presented by their native partners. Interestingly, the 3D reconstructions by negative stain EM reveal a side port in the C3PO/ssRNA complex, and the 15Å cryoEM map showed extra density right above the side port, which probably represents the ssRNA. These results suggest a new way for ssRNAs to interact with the active sites of the complex. Together our data demonstrate that the surface-engineered carbon films are suitable for selectively enriching low-abundance biological complexes at nanomolar level and for developing novel applications on a large number of surface-presented molecules.