Large negative differential resistance and rectifying behaviors in isolated thiophene nanowire devices.

We design isolated molecular nanowires composed of thiophene oligomers sandwiched between two one-dimensional gold electrodes. Electronic transport through the molecular junctions with two interface geometries is studied by performing the first principles calculations based on density functional theory and nonequilibrium Green's function. The current-voltage (I-V) curves of the molecular wires display an unexpected negative differential resistance and rectifying behaviors along with the oscillation effects, different from other theoretical and experimental studies about the analogous thiophene devices. The significant difference is attributed to the design of the one-dimensional gold electrodes with large enough vacuum layer in transverse direction in order to suppress the interaction between wires. Such transport behaviors indicate that the thiophene molecular device would be an important candidate in future molecular electronics.

Nature of the ferromagnetic behavior and possible occurrence of the ferrimagnetic phase transition in genuinely organic molecule-based assemblages with an S = 1 and S = 1/2 antiferromagnetic alternating spin chain: a Green's function approach.

The temperature dependence of magnetic susceptibility and sublattice magnetizations were calculated for a Heisenberg Hamiltonian of an S = 1 and S = 1/2 antiferromagnetic alternating spin chain by means of the many-body Green's function theory to show the possible occurrence of a ferrimagnetic phase transition for genuinely organic molecule-based magnets. The S = 1 site in the chain is composed of two S = 1/2 spins coupled by a finite ferromagnetic interaction. From the calculated results, it is found that the sublattice magnetization at low-spin S = 1/2 sites changes its sign from negative to positive with increasing temperature, giving rise to the spin alignments along the chain changing from antiferromagnetic to ferromagnetic ones, which indicates that there is a magnetic phase transition occurring. Because of the weak intermolecular antiferromagnetic interactions, the curves of the magnetic susceptibility multiplied by temperature (chiT) against temperature show a round peak at low temperatures, which is well consistent with recent experimental observations, and the ferrimagnetic phase transition could only be detected at an ultralow-temperature region and under very weak external magnetic fields in practical organic materials. From the analysis of the sublattice magnetizations, it is uncovered that the appearance of the low-temperature peak in the curves of the chiT originates from the ferromagnetic spin alignments for all the spins along the chain, and the intermolecular antiferromagnetic interactions play a pivotal role in ferrimagnetic spin alignments of the magnetic systems. It is also found that the higher spatial symmetry of the intermolecular antiferromagnetic interactions have contributions to stabilize the ferrimagnetic ordering state in the molecule-based magnetic materials.

Magnetic properties of very-high-spin organic pi-conjugated polymers based on Green's function theory.

Magnetic properties of two very-high-spin organic pi-conjugated polymers have been investigated theoretically by means of the many-body Green's function method with random phase approximation. The polymers are designed with a large density of cross-links and alternating connectivity of radical modules with unequal spin quantum numbers (S), macrocyclic S=2 or 3, and cross-linking S=1/2 modules, which permit large net S values for either antiferromagnetic or ferromagnetic exchange coupling between the modules. The numerical results reveal that, ascribing to the zero-temperature spin fluctuations, the sublattice magnetizations of the two polymers are both smaller than their classical spin values and the ground-state magnetizations of them are also smaller than their predicted values in the antiferromagnetic exchange coupling case. However, these magnetic behaviors do not occur in the ferromagnetic exchange coupling case. On the basis of our synthesis of the temperature dependence of the magnetic susceptibility multiplied by temperature, and through comparing the theoretical results with the experimental measurements, it is concluded that the magnetic exchange couplings between the modules within the two high-spin polymers should be ferromagnetic exchange couplings, which are consistent with other theoretical results drawn from the investigations into the ground-state properties of the two organic polymers.

4-Carboxy-pyridinium 3-carb-oxy-4-hydroxy-benzene-sulfonate.

Cocrystallization of 4-carboxy-pyridine (4-CPY) and 5-sulfosalicylic acid (5-H(2)SSA) yields the title salt, C(6)H(6)NO(2) (+)·C(7)H(5)O(6)S(-). In the crystal structure, the components of the salt are linked by a combination of inter-molecular O-H⋯O and N-H⋯O, and weak C-H⋯O hydrogen bonds, forming a three-dimensional framework.

Bis(2-methyl-imidazolium) chloranilate.

The asymmetric unit of the title structure, 2C(4)H(7)N(2) (+)·C(6)Cl(2)O(4) (2-), consists of one 2-methyl-imidazolium cation and one-half of a chloranilate anion, the formula unit being generated by crystallographic inversion symmetry. N-H⋯O hydrogen bonds link the ions into a two-dimensional framework parallel to the (102) plane. No π-π stacking or C-H⋯π inter-actions are observed in the crystal structure.

[Effect of different intensities of electroacupuncture stimulation on expression of SOCS-3 and PPAR-gamma mRNA in adipose tissues of obesity rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on the expression of suppressor of cytokine signaling 3 (SOCS-3) and peroxisome proliferator-activated receptor (PPAR)-gamma genes in the epididymis adipose tissue of obesity rats so as to explore its mechanism underlying weight reduction. METHODS: SD rats were randomized into normal control, obesity model, EA-5 mA and EA-1 mA groups (10 rats/group). EA stimulation (6 Hz/20 Hz, 5 mA or 1 mA) was delivered to the bilateral "Zusanli" (ST 36) and "Sanyinjiao" (SP 6) for 15 min, once everyday for two weeks. The expression of SOCS-3 mRNA and PPAR-gamma mRNA in the epididymis adipose tissue was detected by reverse transcriptase polymerase chain reaction. RESULTS: Compared with the normal group, the body weight and expression of SOCS-3 and PPAR-gamma mRNA in the model group were up-regulated obviously (P < 0.01). Compared with the model group, the body weight and expression of SOCS-3 and PPAR-gamma mRNA were significantly decreased in the EA group, with the effects of EA-5 mA being better than those of EA-1 mA. CONCLUSION: EA stimulation of ST 36-SP 6 can reduce body weight in rats with simple obesity, and the effect of higher intensity of EA is apparently better. Accordingly, EA intervention induces down-regulation of SOCS-3 and PPAR-gamma mRNA expression in the epididymis adipose tissue.

[Effect of different intensities of electroacupuncture on expression of monocyte chemoattractant protein-1 and TNF-alpha in adipose tissue in obesity rats].

OBJECTIVE: To observe the effect of different intensities of electroacupuncture (EA) on adipose tissue inflammatory cytokines in rats with simple obesity so as to investigate its mechanism underlying body weight reduction. METHODS: Forty SD male rats were randomly divided into normal, model, strong EA and weak EA groups (n = 10/group). Obesity model was established by feeding the rats with high fat diet. EA (20 Hz, strong EA: 5 V, weak EA: 2. 5 V) was applied to "Zusanli" (ST 36) and "Sanyinjiao" (SP 6) for 15 min, once everyday and for 14 days. Body weight and Lee's index (= body weight(1/3) x 10(3) / body length) were detected. The fasting blood glucose was detected by hexokinase method, serum triglyceride (TG) was detected by glycerol-phosphoric acid oxidase peroxydase (GPO-POD)method, total cholesterol (TC) was detected by cholesterol oxidase method, high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-O) were measured by using one-step method, respectively. The expression of monocyte chemoattractant protein-1 (MOP-1) mRNA and tumor necrosis factor (TNF)-alpha mRNA in the epididymis adipose tissue was detected by reverse transcription-polymerase chain reaction (RT-POR). RESULTS: In comparison with the normal group, the body weight, Lee's index, blood lipid (TG, TC, LDL-C), fasting blood glucose levels, and expression of MOP-1 mRNA and TNF-alpha mRNA were significantly higher in the model group (P < 0.01), and HDL-C was significantly lower (P < 0.01). After EA,compared with the model group, the body weight, Lee's index, TG, TC, LDL-C, fasting blood glucose levels, and expression of MCP-1 mRNA and TNF-a mRNA in both strong and weak EA groups were significantly decreased (P < 0.01, P < 0.05), and HDL-C was significantly increased (P < 0.01, P < 0.05). The effects of strong EA group were obviously superior to those of weak EA group (P < 0.05, P < 0.01). No statistical significance was observed between the two EA groups in fasting blood glucose levels (P > 0.05). CONCLUSION: EA of "Zusanli" (ST 36) and "Sanyinjiao" (SP 6) has a beneficial weight-reduction effect on rats with simple obesity, and moreover, the effect of strong EA stimulation is evidently superior to weak EA stimulation.

Magnetic properties and quantum phase transitions of purely organic molecule-based ferrimagnets based on Green's function theory.

Magnetic properties of a Heisenberg diamondlike spin chain model for purely organic molecule-based ferrimagnets are investigated by means of the many-body Green's function method within random phase approximation. The molecule-based ferrimagnet is composed of S=1 biradical and S=1/2 monoradical molecules alternating with intermolecular antiferromagnetic (AF) interactions, and the S=1 site is composed of two S=1/2 spins by a finite intramolecular ferromagnetic (F) interaction. The numerical results reveal that occurrence of ferrimagnetic spin alignments along the chain is determined by the intermolecular AF interactions. Owing to the very small intermolecular AF interactions, the curves of the product of magnetic susceptibility and temperature (chiT) against temperature display as a round peak at low temperatures, and the ferrimagnetic phase transition could only be detected at ultralow temperatures in practical organic compounds. Temperature- and magnetic-field-induced magnetic phase transitions are discussed, which are consistent with the experimental findings. The lower spatial symmetry of intermolecular interactions makes it easy to form spin pairs with a singlet (S=0) ground state along the chain and to reduce Curie temperature. The formations of molecular dimers and trimers along the chain have contributions to bring about F alignments with effective S=1/2 magnetic supramolecules and to enhance Curie temperature. In addition, the experimental data of the magnetic susceptibility measurements for a molecule-based ferrimagnet are also fairly compared with our theoretical results.