Conformational electroresistance and hysteresis in nanoclusters

The existence of multiple thermodynamically stable isomer states is one of the most fundamental properties of small clusters. This work shows that the conformational dependence of the Coulomb charging energy of a nanocluster leads to a giant electroresistance, where charging induced conformational distortion changes the blockade voltage. The intricate interplay between charging and conformation change is demonstrated in a nanocluster Zn3O4 by combining a first-principles calculation with a temperature-dependent transport model. The predicted hysteretic Coulomb blockade staircase in the current-voltage curve adds another dimension to the rich phenomena of tunneling electroresistance. The new mechanism provides a better controlled and repeatable platform to study conformational electroresistance.

Differences in differential gene expression between young and mature Arabidopsis C58 tumours

Tumorigenesis of plants triggered by Agrobacterium tumefaciens has been investigated for over a century, but a global study on changes in gene expression in plant tumours during growth and development has received little attention so far due to technical difficulties. Recently a great advance in 'omic' technologies, e.g. microarray, proteome and transcriptome analyses, has allowed differential expression profiling of genes for metabolic regulation during plant tumour growth and development. Deeken et al.(The Plant Cell Online, 18, 3617) and Lee C.-W. et al.(The Plant Cell Online, 21, 2948) used a fold change approach to profile genes differentially expressed (DE) between Arabidopsis inflorescence stalks infected with Agrobacterium strains C58 (carrying T-DNA) or GV3101 (without T-DNA) and control stalks at 3 hours, 6 days and 35 days after inoculation. We utilised ranking analysis of microarray data, a modified t-test approach, to further analyse these microarray data and compared DE gene functioning in photosynthesis, energy, nucleotide, RNA, DNA, protein and lipid metabolism, biological defence, cell wall and signalling pathways in young (6-day-old) and mature (35-day-old) tumours. There were large differences in differential expression of genes for these basic metabolic pathways between young and mature tumours. In young tumours, more genes were up-regulated in most metabolic functional categories than down-regulated, whereas in mature tumours, genes involved in basic and major metabolic pathways were more down-regulated than up-regulated, strongly indicating that relative to the control stalk, many metabolic pathways were enhance in young tumours but decayed or tended to be decayed in mature tumours.

Clinical and experimental observations of peripheral blood leukocytes and nucleated bone marrow cells after local irradiation

AIM

Aim of the study was to observe the impact of bone marrow damage induced by local irradiation on leukopenia.

METHODS

For the human study, five cancer patients received local radiation therapy. Bone marrow aspiration was conducted to measure nucleated cell count and 99mTc-Sc sulfur colloid ECT imaging was carried out to examine bone marrow function. For the animal study, fifty New Zealand white rabbits were divided into 3 groups: non-irradiated control group (N.=10), abdomen irradiation group (irradiation area did not cover bone marrow) (N.=20), chest irradiation group (irradiation area covered bone marrow) (N.=20). Nucleated cell counts were taken after confirming onset of leukopenia.

RESULTS

Bone marrow of five patients proliferated normally. ECT imaging showed no abnormality in the pattern of red bone marrow distribution. Hematopoietic function was mildly active.

CONCLUSION

Suppressed myeloproliferative function does not fully account for irradiation-induced leukopenia.

Relationship between blood glucose fluctuation and macrovascular endothelial dysfunction in type 2 diabetic patients with coronary heart disease

OBJECTIVE

To evaluate the relationship between blood glucose fluctuation and macrovascular dysfunction.

PATIENTS AND METHODS

Eighty-eight type 2 diabetes mellitus (T2DM) patients with or without coronary heart disease (CHD) and 30 healthy control subjects were recruited. Glycosylated hemoglobin A1c (HbA1c), fasting insulin (FIns), and C-reaction protein (CRP) and some other general clinical variables were measured. A 72-hour continuous glucose monitoring (CGM) and brachial artery endothelium-dependent flow-mediated dilation (FMD) assessment were performed. The glucose excursion, MAGE (mean amplitude of glycemic excursions), LAGE (largest amplitude of glycemic excursions), MPPGE (mean postprandial glycemic excursions), MODD (absolute means of daily differences), and IAUC70 (incremental area under the curve below 70 mg/dl) during the CGM were analyzed. Correlations between the various variables were analyzed.

RESULTS

Enhanced blood glucose fluctuation was observed in T2DM patients with CHD as compared to other participants. And blood glucose fluctuation was correlated with FMD, CRP and HOMA-IR.

CONCLUSIONS

Blood glucose fluctuation is an important factor that affects inflammatory response and possibly induces CHD in T2DM patients.

Blood glucose fluctuation aggravates lower extremity vascular disease in type 2 diabetes

OBJECTIVES

Lower-extremity vascular diseases are important complication of diabetes. In the present study, we investigated the influence of blood glucose fluctuation in type 2 diabetes-associated lower-extremity vascular diseases, and explore the possible mechanism.

PATIENTS AND METHODS

Patients with type 2 diabetes was assigned to Group B (without lower-extremity vascular disease) and group C (with lower-extremity vascular disease). Healthy subjects (Group A) served as normal controls. All patients received dynamic blood glucose monitoring for 72 h. The mean amplitude of glycemic excursion (MAGE) and the largest amplitude of glycemic excursion (LAGE) were estimated. The levels of von Willebrand factor (vWF), ischemia-modified albumin (IMA), glycosylated hemoglobin (HbA1c), and biochemical indices were examined, and the lower-extremity vascular diseases were scored in patients from group C.

RESULTS

Groups B and C have higher systolic blood pressure (SBP), total cholesterol (TC) level, high-density lipoprotein cholesterol (HDL-C) level, HbA1c level, and vWF level and lower IMA level than those in Group A (p < 0.05). Elevated MAGE and LAGE were observed in groups B and C as compared with Group A. Correlation analysis revealed that the score of lower-extremity vascular diseases was associated with MAGE, LAGE, SBP, LDL-C, vWF, HbA1c, and IMA (p < 0.05). Stepwise multiple-linear regression analysis revealed that lower-extremity vascular diseases were involved with MAGE, IMA, and vWF.

CONCLUSIONS

Enhanced fluctuation in patients with type 2 diabetes may promote the occurrence and development of lower-extremity vascular diseases through aggravating vascular endothelial injury.

Clinical and experimental observation of the length of time of respiratory phase: a preliminary study

OBJECTIVE

Our goal was to observe the duration of inhaling and exhaling as well as the inhalation to exhalation conversion in patients with lung cancer and experimental dogs.

MATERIALS AND METHODS

We recorded lung and tumor respiratory motion with X-ray camera, in five patients with lung cancer as well as in five experimental dogs. We made random observation of breathing cycle inhalation duration, exhalation duration, and inhalation to exhalation conversion within each lung cancer patients and within each of the five animals.

RESULTS

Respiratory inhalation duration of each dog and human > exhalation duration > exhale to inhale conversion length > inhalation to exhalation conversion length. During the four breathing cycles, the total respiratory duration differs, and the length of the same breathing phase is inconsistent.

CONCLUSIONS

The measurement of early stage breathing duration cannot be representative of breathing duration of the late stage. Radiation treatment planning system based on the pre-computed tomography scanning on the basis of early stage, there will be some radiation dose errors.

Ultrasound-guided ablative therapy for hepatic malignancies : a comparison of the therapeutic effects of microwave and radiofrequency ablation

BACKGROUND

Radiofrequency ablation (RFA) is currently the most widely used thermal ablative technique for unresectable hepatic malignancies. However, microwave ablation (MWA) is also gaining popularity worldwide. With a cooled-tip electrode, MWA produces necrotic effects comparable to RFA without damaging soft tissues along the electrode track. In this study, the authors compared the efficacy of these two ablative modalities in the treatment of primary or secondary liver cancer.

MATERIALS AND METHODS

Ultrasound-guided MWA was employed to treat 230 cases of liver cancer with a total of 349 nodules and a diameter of 0.8-11.4 cm [mean: 5.7 +/- 2.1 cm]. Meanwhile, ultrasound-guided RFA was performed in 92 cases of liver cancer with 173 nodules in total and a diameter of 2.0-10.2 cm [mean: 5.4 +/- 1.9 cm]. The clinical data were retrospectively analyzed to identify the differences between MWA and RFA in terms of their operative safety, local ablative effect, cost efficiency, and cumulative survival rate.

RESULTS

The patient parameters were comparable. The area of coagulative necrosis was similar in both groups. The tumor complete ablation rate was 83.7% (292/349) for the MWA group and 86.7% (150/173) for the RFA group, which showed no significant difference (P = 0.75). The one-year and two-year cumulative survival rate were all comparable between the two groups (P = 0.66, P = 0.41), which were 90.0% (198/220), 81.6% (120/147) for the MWA group, and 91.8% (78/85), 81.0% (34/42) for the RFA group, respectively. Moreover, both the tumor type and number had no influence on survival rate for the two methods. In addition, there was no significant difference in complication rates between the two groups. The cost for performing one MWA procedure was about 40% lower than that of RFA ($1200 vs $2000).

CONCLUSIONS

Both MWA and RFA are safe and effective ablative treatments for liver cancer. Additionally, MWA has the advantage of cost efficiency.

Spatially resolved mapping of electrical conductivity across individual domain (grain) boundaries in graphene

All large-scale graphene films contain extended topological defects dividing graphene into domains or grains. Here, we spatially map electronic transport near specific domain and grain boundaries in both epitaxial graphene grown on SiC and CVD graphene on Cu subsequently transferred to a SiO2 substrate, with one-to-one correspondence to boundary structures. Boundaries coinciding with the substrate step on SiC exhibit a significant potential barrier for electron transport of epitaxial graphene due to the reduced charge transfer from the substrate near the step edge. Moreover, monolayer-bilayer boundaries exhibit a high resistance that can change depending on the height of substrate step coinciding at the boundary. In CVD graphene, the resistance of a grain boundary changes with the width of the disordered transition region between adjacent grains. A quantitative modeling of boundary resistance reveals the increased electron Fermi wave vector within the boundary region, possibly due to boundary induced charge density variation. Understanding how resistance change with domain (grain) boundary structure in graphene is a crucial first step for controlled engineering of defects in large-scale graphene films.

Giant molecular magnetocapacitance

Through investigating the spin-dependent charging energy of nanoscale systems, we introduce a new concept of intrinsic molecular magnetocapacitance (MC). In molecules and nanosize quantum dots that undergo a spin state transition, the MC can be as high as 12%. First-principles calculations demonstrate that in a number of nanoscale systems, the quantum capacitance is highly sensitive to the system spin and charge states. In single molecule junctions, one can exploit molecular MC through the Coulomb blockade effect by modulating the bias voltage and applying an external magnetic field, which turns electron conductance on or off. Detailed analysis on molecular nanomagnet Mn(3)O(sao)(3)(-)(O(2)CMe)(H(2)O)(py)(3) shows a 6% MC with a switching field of ~40 T. Its MC can be further enhanced to 9.6% by placing the molecule above a dielectric surface, opening up new avenues for novel nanoscale materials design. Under current experimental conditions, the predicted molecular MC effect can be probed without substantial difficulties.

Differential expression of lipid metabolism genes in the liver and adipose tissue of mice treated with evodiamine

Evodiamine is the main active alkali of Wu Zhuyu, a widely distributed Chinese herb. It plays an important role in the regulation of body fat deposition. In this study, we aimed to investigate the effect of evodiamine administration on the expression of genes involved in lipid metabolism in the liver and adipose tissue. Fasted mice were subcutaneously injected with evodiamine (37 °C, 20 mg/kg), and the core body temperature change and expression levels of lipid metabolism-related genes were evaluated at baseline, 0.5, 1, and 2 h. We detected the mRNA expression of fatty acid synthesis enzyme (FAS), peroxisome proliferator-activated receptor gamma (PPAR-γ), sterol regulatory element binding protein 1c (SREBP-1c), triglyceride hydrolase (TGH), and hormone-sensitive lipase (HSL) by real-time PCR and analyzed their correlation with core body temperature. Our results showed that the core body temperature was reduced greater than 1 °C with evodiamine treatment at 1 and 2 h (P < 0.01). In mouse livers, SREBP-1c, HSL, and TGH mRNA expression was significantly increased, and they reached the highest levels 1 h after injection (P < 0.01). However, PPAR-γ mRNA expression was decreased and reached a significant level at 0.5 h (P < 0.01) and FAS mRNA expression was not significantly different; FAS and SREBP-1c mRNA expression were reduced and reached significant levels at 1 h (P < 0.01). Of note, other genes demonstrated opposite changes in adipose tissue, and HSL mRNA expression was significantly reduced at 0.5 h (P < 0.01). The decreasing core temperature had a significant negative correlation with the expression of TGH, HSL, FAS, and SREBP- 1c mRNA in the liver (P < 0.01), but had significant positive correlation with levels of FAS and SREBP-1c mRNA in adipose tissue (P < 0.01). In light of these results, the main mechanism of the regulation of body fat deposition by evodiamine is raising energy consumption through reducing body temperature and promoting fat decomposition.

Neonatal sevoflurane anesthesia induces long-term memory impairment and decreases hippocampal PSD-95 expression without neuronal loss

AIM

Volatile anesthetics are widely used in the clinic, and sevoflurane is the most prevalent volatile anesthetic in pediatric anesthesia. Recent findings question the potential risks of volatile anesthetics on brain development. Evidence suggests that sevoflurane may cause neuronal deficiency. This study investigates the long-term effect of sevoflurane in the developing brain.

MATERIALS AND METHODS

We anesthetized 7 day-old rats for 4 h with 2.5% sevoflurane. A Morris water maze was used to evaluate hippocampal function 7 weeks after sevoflurane exposure. Nissl staining was performed to analyze neuronal loss. PSD-95 (postsynaptic density protein-95) expression in the hippocampus was measured using a western blot.

RESULTS

The exposure to 2.5% sevoflurane caused long-term deficits in hippocampal function and decreased hippocampal PSD-95 expression without neuronal loss. This study demonstrates that P7 rats exposed for 4 h to 2.5% sevoflurane have significant spatial learning and memory impairment 7 weeks after anesthesia. In addition, PSD-95 expression in the hippocampus decreased at P56 without neuronal loss.

CONCLUSIONS

These data suggest that sevoflurane causes neurotoxicity in the developing brain, which may be attributed to decreased PSD-95 in the hippocampus.

Biodegradable and redox-responsive chitosan/poly(L-aspartic acid) submicron capsules for transmucosal delivery of proteins and peptides

The development of peptides and proteins is hampered by their rapid clearance in liver and other body tissues by proteolytic enzymes, so these drugs are difficult to administer except for the injection. Here, we designed and fabricated a novel biodegradable and redox-responsive submicron capsules through the layer-by-layer technique with poly(L-aspartic acid) and chitosan for transmucosal delivery of proteins and peptides. TEM graphs reveal that the intact submicron capsules were obtained and the shell of submicron capsules was about 40 nm. The mucoadhesion test indicates that the adsorption amount of the mucin could achieve up to 96.2 μg per 2 mg. The cell viability test shows that all types of submicron capsules had good cytocompatibility and the cell viability was above 90 %. As a drug model, the insulin could be loaded in the submicron capsules, and the loading efficiency was about 5 %. The release amount of insulin could be regulated by the levels of GSH. Therefore, the mucoadhesive submicron capsules as vehicles have a potential for the mucosal delivery (e.g. nasal and buccal) of therapeutic peptide and protein drugs.

RNA interference targeting extracellular matrix metalloproteinase inducer (CD147) inhibits growth and increases chemosensitivity in human cervical cancer cells

Overexpression of extracellular matrix metalloproteinase (MMP) inducer (EMMPRIN CD147) has been implicated in the growth and survival of malignant cells. However, its presence and role in cervical cancer cells has not been well-studied. In the present study, small interfering RNA (siRNA) was designed and synthesized to breakdown the expression of CD147. The present data demonstrated that 24 and 48 hours after transfecting CD147 siRNA, both the CD147 mRNA and protein expression were significantly inhibited as determined by quantitative real-time polymerase chain reaction (RT-PCR) and immunocytochemistry. Meanwhile, simultaneous silencing of CD147 resulted in distinctly increasing MMP-9, VEGF, and MDR-1. Further studies demonstrated decreased CD147 expression, resulted in G1/S phase transition with flow cytometry analysis, as well as the resistance of the cells to 5-FU. These findings provide further evidence that CD147 may become a promising therapeutic target for human cervical cancer and a potential chemotherapy-sensitizing agent.

Accuracy of noninvasive quantification of brain NAA concentrations using PRESS sequence: verification in a swine model with external standard

The metabolite ratios had been employed in the field of MR spectroscopy (MRS) for a long period. The main drawback of metabolite ratio is that ratio results are not comparable with absolute metabolite concentration in vivo. The purpose of this study was to examine the accuracy of noninvasive quantification of brain N-acetylaspartate (NAA) concentrations using previously reported MR external standard method. Eight swine were scanned on a GE 1.5 T scanner with a standard head coil. The external standard method was utilized with a sphere filled with NAA, GABA, glutamine, glutamate, creatine, choline chloride, and myo-inositol. The position resolved spectroscopy (PRESS) sequence was used with TE=135 msec, TR=1500 msec, and 128 scan averages. The analysis of MRS was done with SAGE/IDL program. In vivo NAA concentration was obtained using the equation S=N * e(-TE/T₂) * [1-e(-TR/T₁). In vitro NAA concentration was measured by high performance liquid chromatography (HPLC). In the MRS group, the mean concentration of NAA was 10.03 plusmn 0.74 mmol/kg. In the HPLC group, the mean concentration of NAA was 9.22 plusmn 0.55 mmol/kg. There was no significant difference between the two groups (p = 0.46). However, slightly higher value was observed in the MRS group (7/8 swine), compared with HPLC group. The range of differences was between 0.02~2.05 mmol/kg. MRS external reference method could be more accurate than internal reference method. ¹H MRS does not distinguish between N-acetyl resonance frequencies and other N-acetylated amino acids.

Theory of space charge limited currents

Space-charge-limited currents are important in energy devices such as solar cells and light-emitting diodes, but the available theory from the 1950s finds it necessary to postulate defect states that are distributed in energy in order to match data. Here, we show that this postulate is not warranted. Instead, we demonstrate that dopants and the concomitant Frenkel effect, which have been neglected, control the shape of measured current-voltage characteristics. We also account for the observed peak in the noise power. The new theory can anchor efforts to develop experimental techniques to measure deep-trap levels.

Nanoscale periodic modulations on sodium chloride surface revealed by tuning fork atomic force microscopy

The sodium chloride surface is one of the most common platforms for the study of catalysts, thin film growth, and atmospheric aerosols. Here we report a nanoscale periodic modulation pattern on the surface of a cleaved NaCl single crystal, revealed by non-contact atomic force microscopy with a tuning fork sensor. The surface pattern shows two orthogonal domains, extending over the entire cleavage surface. The spatial modulations exhibit a characteristic period of 5.4 nm, along <110> crystallographic directions of the NaCl. The modulations are robust in vacuum, not affected by the tip-induced electric field or gentle annealing (<300 °C); however, they are eliminated after exposure to water and an atomically flat surface can be recovered by subsequent thermal annealing after water exposure. A strong electrostatic charging is revealed on the cleavage surface which may facilitate the formation of the observed metastable surface reconstruction.

Interface characterization of epitaxial Fe/MgO/Fe magnetic tunnel junctions

Following predictions by first-principles theory of a huge tunnel magnetoresistance (TMR) effect in epitaxial Fe/MgO/Fe magnetic tunnel junctions (MTJs), measured magnetoresistance (MR) ratios of about 200% at room temperature (RT) have been reported in MgO-based epitaxial MTJs. Recently, a MR ratio of about 600% has been reported at RT in MgO-based MTJs prepared by magnetron sputtering, using amorphous CoFeB as the ferromagnetic electrode. These MTJs show great potential for application in spintronic devices. Fully epitaxial MTJs are excellent model systems that enhance our understanding of the spin-dependent tunneling process as the interface is well defined and can be fully characterized. Both theoretical calculations and experimental results clearly indicate that the interfacial structure plays a crucial role in the coherent tunneling across a single crystal MgO barrier, especially in epitaxial MgO-based MTJs grown by molecular beam epitaxy (MBE). Surface X-ray diffraction, Auger electron spectroscopy, X-ray absorption spectra, and X-ray magnetic circular dichroism techniques have been reported previously for interface characterization. However, no consistent viewpoint has been reached on the interfacial structures (such as FeO layer formation at the bottom Fe/MgO interface), and it is still an open issue. In this article, our recent studies on the interface characterization of MgO-based epitaxial MTJs by X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and spin-dependent tunneling spectroscopy, will be presented.

Successful therapy with hemoperfusion and plasma exchange in acute 1,2,3-trichloropropane poisoning

1,2,3-trichloropropane (1,2,3-TCP) is commonly used as an intermediate in pesticide and an industrial specialty solvent. Acute 1,2,3-TCP poisoning is rare but a medical emergency. Sporadic cases of toxic hepatic injury from 1,2,3-TCP in humans have been reported. Liver is a target organ for 1,2,3-TCP toxicity, which may ensue in a short period after ingestion. A specific antidote against 1,2,3-TCP is not available. So it is important to distinguish that a patient with 1,2,3-TCP poisoning constitutes a medical emergency. In this case study, the poisoned patient's clinical condition and laboratory values improved gradually after she received hemoperfusion (HP) and plasma exchange, which indicated that the therapy with HP and plasma exchange were helpful in the treatment of 1,2,3-TCP poisoning.

Lack of association of variants of the renal salt reabsorption-related genes SLC12A3 and ClC-Kb and hypertension in Mongolian and Han populations in Inner Mongolia

Abnormalities in renal sodium chloride and water reabsorption play important roles in the development of hypertension. Mutations in the genes involved in renal sodium chloride reabsorption can affect blood pressure. Recently, the R904Q variant of the sodium/chloride transporters, member 3 (SLC12A3) gene and the T481S variant of the chloride channel Kb (ClC-Kb) gene were found to be implicated in essential hypertension. We investigated a possible role of the SLC12A3 and ClC-Kb genes in the prevalence of essential hypertension in the Mongolian and Han ethnic groups. The study population comprised 308 unrelated Mongolians with essential hypertension, 271 Mongolian normotensives, 285 unrelated Han with essential hypertension, and 194 Han normotensives living in Inner Mongolia. The presence of the SLC12A3 R904Q and ClC-Kb-T481S polymorphisms was determined using TaqMan PCR. The risk factors for hypertension were age, body mass index, alcohol consumption, total plasma cholesterol, and low-density lipoprotein cholesterol. The genotype and allele frequencies of SLC12A3 R904Q and ClC-Kb-T481S were not significantly different between hypertensive patients and controls in the Mongolian (SLC12A3 R904Q, P = 0.471 and P = 0.494, ClC-Kb-T481S, P = 0.960 and P = 0.960, respectively) and Han (SLC12A3 R904Q, P = 0.765 and P = 0.777, ClC-Kb-T481S, P = 0.100 and P = 0.103, respectively) populations. There was no significant association between the SLC12A3 R904Q variant and the ClC-Kb-T481S variant and essential hypertension in either ethnic group.

Identification of 18 genes encoding necrosis-inducing proteins from the plant pathogen Phytophthora capsici (Pythiaceae: Oomycetes)

Phytophthora capsici is an aggressive plant pathogen that affects solanaceous and cucurbitaceous hosts. Necrosis-inducing Phytophthora proteins (NPPs) are a group of secreted toxins found particularly in oomycetes. Several NPPs from Phytophthora species trigger plant cell death and activate host defense gene expression. We isolated 18 P. capsici NPP genes, of which 12 were active during hypha growth from a Phytophthora stain isolated from pepper (Capsicum annuum) plants in China. The 18 predicted proteins had a sequence homology of 46.26%. The 18 Pcnpp sequences had a conserved GHRHDWE motif and fell into two groups. Eleven sequences in group 1 had two conserved cysteine residues, whereas the other seven sequences in group 2 lacked these two cysteine residues. A phylogenetic tree was constructed on the basis of the alignment of the predicted protein sequences of 52 selected NPP genes from oomycetes, fungi and bacteria from Genbank. The tree did not rigorously follow the taxonomic classification of the species; all the NPPs from oomycetes formed their own clusters, while fungal sequences were grouped into two separate clades, indicating that based on NPPs, we can separate oomycetes from fungi and bacteria, and that expansion of the NPP family was a feature of Phytophthora evolution.

Hierarchically structured carbon-based composites: Design, synthesis and their application in electrochemical capacitors

This feature article provides an overview of the recent research progress on the hierarchically structured carbon-based composites for electrochemical capacitors. The basic principles of electrochemical capacitors, and the design, construction and performance of hierarchically structured carbon-based composites electrode materials with good ions and electron transportation and large specific surface area are discussed. The trend of future development of high-power and large-energy electrochemical capacitors is proposed.

Large discrete resistance jump at grain boundary in copper nanowire

Copper is the current interconnect metal of choice in integrated circuits. As interconnect dimensions decrease, the resistivity of copper increases dramatically because of electron scattering from surfaces, impurities, and grain boundaries (GBs) and threatens to stymie continued device scaling. Lacking direct measurements of individual scattering sources, understanding of the relative importance of these scattering mechanisms has largely relied on semiempirical modeling. Here we present the first ever attempt to measure and calculate individual GB resistances in copper nanowires with a one-to-one correspondence to the GB structure. Large resistance jumps are directly measured at the random GBs with a value far greater than at coincidence GBs and first-principles calculations. The high resistivity of the random GB appears to be intrinsic, arising from the scaling of electron mean free path with the size of the lattice relaxation region. The striking impact of random GB scattering adds vital information for understanding nanoscale conductors.

Synergistic effects of beta-aescin and 5-fluorouracil in human hepatocellular carcinoma SMMC-7721 cells

The effects and mechanisms of action of beta-aescin and 5-fluorouracil (5-FU), alone and in combination, were studied in human hepatocellular carcinoma SMMC-7721 cells. Growth inhibition, cell cycle distribution, apoptosis, Bcl-2 expression and caspase activity were assessed. The Isobole-method/interaction-index analysis was applied to evaluate the synergy, additivity or antagonism of these agents. The results indicate that mixtures of beta-aescin and 5-FU showed a synergistic effect on the 50% inhibitory effect when their ratio was 4:1 when compared with either agent alone. The mechanism of action could be through the synergistic arrest of the cell cycle, induction of apoptosis, activation of caspases-3, 8 and 9, and down-regulation Bcl-2 expression. The results suggest that mixtures of these two agents had a synergistic inhibitory effect on SMMC-7721 cells, an observation which might be useful for the further development of anti-cancer drugs.

Giant magnetoresistance in organic spin valves

Interfacial diffusion between magnetic electrodes and organic spacer layers is a serious problem in the organic spintronics which complicates attempts to understand the spin-dependent transport mechanism and hurts the achievement of a desirably high magnetoresistance (MR). We deposit nanodots instead of atoms onto the organic layer using buffer layer assist growth. Spin valves using this method exhibit a sharper interface and a giant MR of up to ∼300%. Analysis of the current-voltage characteristics indicates that the spin-dependent carrier injection correlates with the observed MR.