Squarefree P-modules and the cd-index

In this paper, we introduce a new algebraic concept, which we call squarefree P-modules. This concept is inspired from Karu's proof of the non-negativity of the cd-indices of Gorenstein* posets, and supplies a way to study cd-indices from the viewpoint of commutative algebra. Indeed, by using the theory of squarefree P-modules, we give several new algebraic and combinatorial results on CW-posets. First, we define an analogue of the cd-index for any CW-poset and prove its non-negativity when a CW-poset is Cohen–Macaulay. This result proves that the h-vector of the barycentric subdivision of a Cohen–Macaulay regular CW-complex is unimodal. Second, we prove that the Stanley–Reisner ring of the barycentric subdivision of an odd dimensional Cohen–Macaulay polyhedral complex has the weak Lefschetz property. Third, we obtain sharp upper bounds of the cd-indices of Gorenstein* posets for a fixed rank generating function.     

Synthesis and hybridization properties of 2′-O-(tetrazol-5-yl)ethyl-modified oligonucleotides

2′-O-(1H-Tetrazol-5-yl)ethyladenosine was synthesized using 2′-O-cyanoethyladenosine derivative as a key intermediate. The 2′-O-(1H-tetrazol-5-yl)ethyl modifications exhibited intriguing properties such as the change in the structure of the tetrazole residue between a protonated and a deprotonated form. The T_m experiments of various oligodeoxynucleotides having a 2′-O-(1H-tetrazol-5-yl)ethyl-modified adenosine showed reduced hybridization affinity in comparison to the unmodified oligonucleotides toward their complementary oligodeoxynucleotides. The mechanism of the reduced hybridization affinity was discussed on the basis of the structure and the physicochemical properties of the tetrazole moiety.     

Glucose sensor using a phospholipid polymer-based enzyme immobilization method

An electroenzymatic glucose sensor based on a simple enzyme immobilization technique was constructed and tested. The glucose sensor measures glucose concentrations as changes of oxygen concentrations induced by enzymatic reactions. The immobilizing procedure was developed with the purpose of producing wearable biosensors for clinical use. Two types of biocompatible polymers, 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymerized with dodecyl methacrylate (PMD) and MPC copolymerized with 2-ethylhexyl methacrylate, were compared as a sensitive membrane of biosensors. The PMD enzyme membrane had a better response time. Linearity, reproducibility, effect of the concentrations of immobilized enzyme and drifts of sensor characteristics in long-term tests were also investigated. The linear characteristics were confirmed with glucose concentration from 0.01 to 2.00 mmol/l, with a coefficient of determination of 0.9999. The average output current for 1 mmol/l and the standard deviation were 0.992 and 0.0283 muA. Significant changes in the sensor's characteristics were not observed for 2 weeks when it was kept in a refrigerator at 4 degrees C. Because of the simple procedure, the enzyme immobilization method is not only useful for wearable devices but also other devices such as micro total analysis systems.     

DNA duplexes and triplex-forming oligodeoxynucleotides incorporating modified nucleosides forming stable and selective triplexes

We have previously reported DNA triplexes containing the unnatural base triad G-PPI·C3, in which PPI is an indole-fused cytosine derivative incorporated into DNA duplexes and C3 is an abasic site in triplex-forming oligonucleotides (TFOs) introduced by a propylene linker. In this study, we developed a new unnatural base triad A-ψ·C(R1) where ψ and C(R1) are base moieties 2'-deoxypseudouridine and 5-substituted deoxycytidine, respectively. We examined several electron-withdrawing substituents for R1 and found that 5-bromocytosine (C(Br)) could selectively recognize ψ. In addition, we developed a new PPI derivative, PPI(Me), having a methyl group on the indole ring in order to achieve selective triplex formation between DNA duplexes incorporating various Watson-Crick base pairs, such as T-A, C-G, A-ψ, and G-PPI(Me), and TFOs containing T, C, C(Br), and C3. We studied the selective triplex formation between these duplexes and TFOs using UV-melting and gel mobility shift assays.     

Optimum hot electron production with low-density foams for laser fusion by fast ignition

We propose a foam cone-in-shell target design aiming at optimum hot electron production for the fast ignition. A thin low-density foam is proposed to cover the inner tip of a gold cone inserted in a fuel shell. An intense laser is then focused on the foam to generate hot electrons for the fast ignition. Element experiments demonstrate increased laser energy coupling efficiency into hot electrons without increasing the electron temperature and beam divergence with foam coated targets in comparison with solid targets. This may enhance the laser energy deposition in the compressed fuel plasma.     

Factors governing the three-dimensional hydrogen-bond network structure of poly(m-phenylene isophthalamide) and a series of its model compounds (4): similarity in local conformation and packing structure between a complicated three-arm model compound and the linear model compounds

Crystal structure of a three-arm model compound of poly(m-phenylene isophthalamide) (PMIA), N,N',N' '-triphenyl trimesamide Phi(CONHPhi)(3), has been analyzed by the X-ray diffraction method. The torsional angles around the bonds connecting the amide group and the central benzene ring are 24-34 degrees , almost the same as those observed for many kinds of aromatic amide compounds, reflecting mainly the intramolecular energetic balance between the amide and benzene groups. On the other hand, the torsional angles around the bonds connecting the amide group and the outer benzene ring were found to distribute over a wide range of 2-51 degrees due to the additional effect of intermolecular interactions. This is the first example to show experimentally clearly the role of intra- and intermolecular interactions in the control of torsional angle around the benzene-amide linkage. The hydrogen bonds are formed between the amide groups of the neighboring molecules, resulting in the construction of three-dimensional network structure. The local packing structure of the three-arm compound was found to be essentially the same as those observed for PMIA and the linear model compounds, indicating a characteristic structural feature of the meta-linkage-type aromatic amide compounds. The energy calculation was made using the software Polymorph Predictor to extract the energetically most stable crystal structure, which was compared successfully with the X-ray analyzed structure.     

Supramolecular structure of N,N-Bis(2-hydroxybenzyl)alkylamine: flexible molecular assembly framework for host without guest and host with guest

N,N-Bis(2-hydroxybenzyl)alkylamine derivatives form a cage-like assembly consisting of two molecules via inter- and intramolecular hydrogen bonds. The derivatives exhibit themselves as host to accept copper-ion guests under the double-oxygen-bridged dimeric system. Quantum chemical calculation suggested that the host-guest interaction is based on a charge-transfer coordination. Comparison of the crystal structures before and after complexation clarifies a rare example of a host-guest compound where the hosts maintain their cage framework through the change of hydrogen bonds to coordination bonds.     

Castelnuovo-Mumford regularity for complexes and weakly Koszul modules

Let A be a noetherian AS-regular Koszul quiver algebra (if A is commutative, it is essentially a polynomial ring), and the category of finitely generated graded left A-modules. Following Jørgensen, we define the Castelnuovo-Mumford regularity of a complex in terms of the local cohomologies or the minimal projective resolution of M^•. Let A^! be the quadratic dual ring of A. For the Koszul duality functor , we have . Using these concepts, we interpret results of Martinez-Villa and Zacharia concerning weakly Koszul modules (also called componentwise linear modules) over A^!. As an application, refining a result of Herzog and Römer, we show that if J is a monomial ideal of an exterior algebra E=?〈y₁,…,y_d〉, d≥3, then the (d−2)nd syzygy of E/J is weakly Koszul.     

Irreversibility lines of layered Fe-based superconductors with thick blocking layers

Irreversibility lines of the layered iron-arsenide superconductors with thick perovskite-type oxide blocking layers have been systematically studied. Five compounds with different interlayer distance between iron layers from 1.5 to 3.0 nm were selected for the magnetization measurements. These compounds showed very large magnetically reversible region. The irreversibility lines of these compounds were found to locate at very low fields compared to the other iron-based superconductors and shift towards lower fields with an increase in the thickness of the blocking layer. In addition, the analysis on the irreversibility line suggested that the change of dimensionality of the vortex system occurs at $T/T_c～0.6$. These results indicate that the electromagnetic anisotropy originated from the layered crystal structure plays a crucial role to determine the irreversibility line and magnetic phase diagram of layered iron arsenides as is the case in the layered cuprates.     

Supramolecular Structure of N,N-Bis(2-hydroxy-benzyl)alkylamine: From Hydrogen Bond Assembly to Coordination Network in Guest Acceptance

N,N-Bis(2-hydroxybenzyl)alkylamine ( HBA ) was described as a model to simplify the supramolecular system of polybenzoxazines. The single crystal X-ray analysis revealed that HBA forms a dimeric assembly based on its simultaneous inter- and intramolecular hydrogen bond network. When the HBA accepted the copper ion, the dimeric assembly HBA changed its primary hydrogen bond network to charge transfer coordination as clarified by the single crystal analysis as well as the superimposed structure based on DMol³ calculation. The supramolecular structure of HBA and copper also exhibited the role of solvent molecules in the packing structure which is a rare example showing the host accepts not only the metal ions but also the neutral molecules in the same time. The cyclization of HBA with esters or ethers to macrocyclic compounds was also an important model reaction to show how the backbone molecules self-stabilized with the hydrogen bond network initiate the simple, effective and efficient macrocyclic reaction.