Cryopreservation of peach palm zygotic embryos

Cryopreservation is a safe and cost-effective option for long-term germplasm conservation of non-orthodox seed species, such as peach palm (Bactris gasipaes). The objective of the present study was to establish a cryopreservation protocol for peach palm zygotic embryos based on the encapsulation-dehydration technique. After excision, zygotic embryos were encapsulated with 3 percent sodium alginate plus 2 M glycerol and 0.4 M sucrose, and pre-treated or not with 1 M sucrose during 24 h, followed by air-drying. Fresh weight water contents of beads decreased from 83 percent and 87 percent to 18 percent and 20 percent for pre-treated or non-pretreated beads, respectively, after 4 h of dehydration. Sucrose pre-treatment at 1 M caused lower zygotic embryo germination and plantlet height in contrast to non-treated beads. All the variables were statistically influenced by dehydration time. Optimal conditions for recovery of cryopreserved zygotic embryos include encapsulation and dehydration for 4 h in a forced air cabinet to 20 percent water content, followed by rapid freezing in liquid nitrogen (-196 degree C) and rapid thawing at 45 degree C. In these conditions 29 percent of the zygotic embryos germinated in vitro. However, plantlets obtained from dehydrated zygotic embryos had stunted haustoria and lower heights. Histological analysis showed that haustorium cells were large, vacuolated, with few protein bodies. In contrast, small cells with high nucleus:cytoplasm ratio formed the shoot apical meristem of the embryos, which were the cell types with favorable characteristics for survival after exposure to liquid nitrogen. Plantlets were successfully acclimatized and showed 41+/-9 percent and 88+/-4 percent survival levels after 12 weeks of acclimatization from cryopreserved and non-cryopreserved treatments, respectively.     

Two-dimensional ultrasound detection with unfocused frequency-randomized signals

A method is described for detecting scattering in two-dimensions using an unfocused ultrasound field created from a continuously driven source array. The frequency of each element on the array is unique, resulting in a field that is highly variant as a function of both time and position. The scattered signal is then received by a single receiving line. The method, as currently written, is valid under the first order Born approximation. To demonstrate the approach, a series of simulations within the frequency range of 0.10-1.25 MHz are performed and compared with a simulated B-Scan in the same frequency range. The method is found to be superior in resolving closely spaced objects, discerning 1.4 mm separation in the radial and 0.5-mm separation in the axial direction. The method was also better able to determine object size, resolving scatters less than 10% of wavelength associated with the center frequency.     

Synthesis and luminescent properties of cis bis-N-heterocyclic carbene platinum(II) bis-arylacetylide complexes

A series of luminescent N-heterocyclic carbene platinum(II) complexes, [(pmim)Pt(C≡C-R)(2)] (R = C(6)H(5) (2), C(6)H(4)OMe (3), C(6)H(2)(OMe)(3) (4), C(6)H(4)NMe(2) (5), C(4)H(3)S (6), C(6)H(4)C≡CC(6)H(5) (7), 1-pyrenyl (8), and C(6)H(4)F (9)), were successfully synthesized using the precursor (pmim)PtI(2), 1 (pmim = 1,1'-dipentyl-3,3'-methylene-diimidazoline-2,2'-diylidene). The X-ray crystal structures of 1, 4, 5, and 7 have been determined. These complexes showed long-lived emission in solution at room temperature. The emission origin of the complexes is tentatively assigned to be from triplet states of predominantly intraligand (IL) character with some mixing of metal-to-ligand charge-transfer (MLCT) character. TD-DFT and DFT calculations have been performed on most of the complexes to ascertain the nature of the excited state. Changes in the alkynyl ligands lead to a change in the absorption and emission maxima seen for these complexes in a potentially predictable way.     

Prodrug design for the potent cardiovascular agent Nω-hydroxy-L-arginine (NOHA): synthetic approaches and physicochemical characterization

N(ω)-Hydroxy-L-arginine (NOHA)--the physiological nitric oxide precursor--is the intermediate of NO synthase (NOS) catalysis. Besides the important fact of releasing NO mainly at the NOS-side of action, NOHA also represents a potent inhibitor of arginases, making it an ideal therapeutic tool to treat cardiovascular diseases that are associated with endothelial dysfunction. Here, we describe an approach to impart NOHA drug-like properties, particularly by wrapping up the chemically and metabolically instable N-hydroxyguanidine moiety with different prodrug groups. We present synthetic routes that deliver several more or less highly substituted NOHA derivatives in excellent yields. Versatile prodrug strategies were realized, including novel concepts of bioactivation. Prodrug candidates were primarily investigated regarding their hydrolytic and oxidative stabilities. Within the scope of this work, we essentially present the first prodrug approaches for an interesting pharmacophoric moiety, i.e., N-hydroxyguanidine.     

Quantitative evaluation of process induced strain in MOS transistors by Convergent Beam Electron Diffraction

Convergent Beam Electron Diffraction (CBED) experiments and simulations associated with Finite Element calculations were performed in order to measure strain and stress in a complex device such as periodic MOS transistors with a spatial resolution of about 2 nm and a sensitivity that could reach 50 MPa. A lamella of a thickness of about 475 nm was extracted from the wafer with the transistors by Focus Ion Beam (FIB) and was observed in cross-section in a Transmission Electron Microscope (TEM). When approaching the transistors, the HOLZ lines of the CBED patterns acquired in the silicon substrate, become broader and broader. This HOLZ line broadening, which is due to the stress relaxation in the thin foil, was used to determine quantitatively the strain and stress in the lamella and then in the bulk device. We showed that this procedure could be applied to a complex device. Two parameters, the intrinsic material strains – or equivalently the intrinsic material stresses – in the nickel silicide (NiSi) and nitride (Si₃N₄) layers on the top of the transistors gate, were successfully fitted by trial and error, in the procedure.     

Single- and double-pion production in nucleon collisions on the nucleon and on nuclei—the ABC effect and its origin in a dibaryonic resonance

The ABC effect-an intriguing low-mass enhancement in the ππ invariant mass spectrum-is known from inclusive measurements of two-pion production in nuclear fusion reactions. First exclusive measurements carried out at CELSIUS-WASA for the fusion reactions leading to d or ³He reveal this effect to be a σ-channel phenomenon associated with the formation of a ΔΔ system in the intermediate state and combined with a resonance-like behavior in the total cross-section. Together with the observation that the differential distributions do not change in shape over the resonance region the features fulfill the criteria of an isoscalar s-channel resonance in pn and NNππ systems, if the two emitted nucleons are bound. It obviously is robust enough to survive in nuclei as a dibaryonic resonance configuration. In this context also the phenomenon of NΔ resonances is reexamined.     

Single \mathrm{\ensuremath{\pi^{-}}} production in np collisions for excess energies up to 90 MeV

The quasifree reaction was studied in a kinematically complete experiment by bombarding a liquid-hydrogen target with a deuteron beam of momentum 1.85GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector _n which differed from event to event. A range of almost 90MeV excess energy above threshold was covered. Energy-dependent angular distributions, invariant-mass spectra as well as fully covered Dalitz plots were deduced. Sizeable pp FSI effects were found as were contributions of p and d partial waves. In comparison with existing literature data the results provide a sensitive test of the spectator model. The behavior of the elementary cross-section σ₀₁ close to threshold is discussed in view of new cross-section data.     

Plasma-enhanced atomic layer deposition of Co using Co（MeCp）2 precursor

Cobalt（Co） thermal or plasma enhanced atomic layer deposition（PE-ALD） was investigated using a novel metal organic precursor,Co（MeCp）₂, and NH₃ or H₂ or their plasma as a reactant.The growth characteristics,electrical and microstructural properties were investigated.Especially, PE-ALD produced Co thin films at low growth temperature down to 100℃.Interestingly,the low temperature growth of Co films showed the formation of columnar structure at substrate temperature below 300℃.The growth characteristics and films properties of PE-ALD Co using bis（η-methylcyclopentadienyl） Co（Ⅱ）（Co（MeCp）₂） was compared with those of PE-ALD Co using other Cp based metal organic precursors, bis-cyclopentadienyl cobalt（II）（CoCP₂） and cyclopentadienyl isopropyl acetarrudinato-cobalt（Co（CpAMD））.     

Synthesis and characterization of physically crosslinked N‐vinylcaprolactam,acrylic acid,methacrylic acid,and N,N‐dimethylacrylamide hydrogels

Physically crosslinked hydrogels based on N‐vinylcaprolactam/acrylic acid and N‐vinylcaprolactam/methacrylic acid were prepared via free radical polymerization. These temperature responsive hydrogels were characterized in terms of glass transition, phase separation temperature, potentiometric titration and swelling properties. Results showed that phase transition temperature was dependent on the pH value of the solution; increasing pH led to higher lower critical solution temperature (LCST) values which was related to the dissociative behaviors of the carboxylic group of MAc in the buffered solutions. Additionally, with the incorporation of N,N‐dimethylacrylamide into the system, cloud point measurements and MDSC showed an increased in the LCST. This increase was based on hydrophilicity, the hydrophilic–hydrophobic balance was disturbed, and consequently, the LCST behavior was shifted. The pKa of the copolymers ranged between 5.6 and 6.5, while for the terpolymers pKa ranged between 5.3 and 6. At high pH (>10), the ? COOH group is deprotonated and negatively charged (? COO^?), while at low pH (1–3) the carboxylic group remains protonated which results in hydrogen bonding between the hydroxyl groups (from NaOH) and the excess of HCl. These results correlate with swelling studies where above the pKa value the hydrogels dissolved rapidly compared to below pKa they did not dissolve at all. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1555–1564