Generating ultrabroadband terahertz radiation based on the under-compression mode of velocity bunching

We propose and analyze a scheme to generate enhanced ultrabroadband terahertz (THz) radiation through coherent transition radiation emitted by ultrashort electron beams based on a 10.5 m beamline at Tsinghua University. The proposed scheme involves the initial compression of the electron beam with a few hundred pC charges using a velocity bunching scheme (i.e., RF compression) in an under-compression mode instead of the usual critical-compression mode in order to maintain a positive energy chirp at the exit of the traveling wave accelerator. After a long drift segment, the particles in the tail catch up with the bunch head. More than 80% of the particles are distributed in a spike with an rms length less than 20 fs. Such beams correspond to an ultrabroadband coherent transition radiation (CTR) spectrum of 0.1 THz to 25 THz, with the single-pulse THz radiation energy of up to 50 μJ. The principle of CTR and under-compression mode of velocity bunching are introduced in this paper. And the ASTRA simulation parameters and the stability of the system are also discussed.

A dairy fat matrix providing alpha-linolenic acid (ALA) is better than a vegetable fat mixture to increase brain DHA accretion in young rats

Achieving an appropriate DHA status in the neonatal brain is an important goal of neonatal nutrition. We evaluated how alpha-linolenic acid (ALA), provided for six weeks after weaning by different dietary fat matrix, improved brain DHA content of young male rats born from deficient-dams. The level of ALA achieved was based on the fat composition of usual infant vegetable formula. A palm oil-blend diet thus providing 1.5%ALA was compared to dairy fat-blend-based diets that provided either 1.5%ALA or 2.3%ALA, or a rapeseed oil diet providing 8.3%ALA (n-6/n-3 ratio were, respectively 10,10,5,2.5). The 1.5%ALA-dairy-fat-blend was superior to 1.5%ALA-palm-oil-blend to restore values of brain DHA, while the 2.3%ALA-dairy-fat-blend exhibited a further increase and reached the values obtained with pure rapeseed diet (8.3%ALA). Dairy-fat-blends enriched with ALA appear to be an interesting strategy for achieving optimal DHA levels in the brain of post-weaning rats. Providing dairy fat as well as a reduction of the LA/ALA ratio should be reconsidered to design infant formula.

Isolation of the retinal isomers from the isomerization of all-trans-retinal by flash countercurrent chromatography

The isolation of the retinal isomers from all-trans-retinal was performed by flash countercurrent chromatography. In each separation, isomerization reaction solution of 200mg all-trans-retinal could be loaded on a 1200 mL of high-speed countercurrent chromatographic column with 5mm bore, eluted by a mobile phase flow rate of 25 mL/min, resulting in 63 mg of 11-cis-retinal, 24 mg of 13-cis-retinal and 26 mg of 9-cis-retinal with purities more than 95%. n-Hexane-acetonitrile (3:1) was used as the solvent system which possesses the advantages of simplicity, re-use of the solvent and multiple injections. This method could be used to prepare 13-cis-retinal, 11-cis-retinal and 9-cis-retinal for the photoisomerization investigation, such as the effect of 11-cis-retinal in the visual system.

Scaling up of high-speed countercurrent chromatographic apparatus with three columns connected in series for rapid preparation of (-)-epicatechin

In the present study, compact high-speed countercurrent chromatographic apparatus was constructed with three columns connected in series. Two sets of columns were prepared from 10 mm and 12 mm I.D. tubing to form 12 L and 15 L capacities, respectively. Performance of these columns was compared for the separation of (-)-epicatechin gallate (ECG) from a tea extract by flash countercurrent chromatography (FCCC). In each separation, 200 g of the tea extract in 1600 mL of mobile phase was loaded onto the column. The 12 L column gave 7.5 L (35 g of ECG) and the 15 L column gave 9 L (40 g of ECG) of ECG solution without impurities. The ECG solution was directly hydrolyzed by tannase into (-)-epicatechin. The hydrolysate was purified by flash chromatography on AB-8 macroporous resin to give 52 g of EC (purity 99.1%). This scaled up apparatus could be used for the industrial separation of natural products.

Mouse hypothalamic GT1-7 cells demonstrate AMPK-dependent intrinsic glucose-sensing behaviour

AIMS/HYPOTHESIS

Hypothalamic glucose-excited (GE) neurons contribute to whole-body glucose homeostasis and participate in the detection of hypoglycaemia. This system appears defective in type 1 diabetes, in which hypoglycaemia commonly occurs. Unfortunately, it is at present unclear which molecular components required for glucose sensing are produced in individual neurons and how these are functionally linked. We used the GT1-7 mouse hypothalamic cell line to address these issues.

METHODS

Electrophysiological recordings, coupled with measurements of gene expression and protein levels and activity, were made from unmodified GT1-7 cells and cells in which AMP-activated protein kinase (AMPK) catalytic subunit gene expression and activity were reduced.

RESULTS

Hypothalamic GT1-7 neurons express the genes encoding glucokinase and ATP-sensitive K(+) channel (K(ATP)) subunits K ( ir ) 6.2 and Sur1 and exhibit GE-type glucose-sensing behaviour. Lowered extracellular glucose concentration hyperpolarised the cells in a concentration-dependent manner, an outcome that was reversed by tolbutamide. Inhibition of glucose uptake or metabolism hyperpolarised cells, showing that energy metabolism is required to maintain their resting membrane potential. Short hairpin (sh)RNA directed to Ampkα2 (also known as Prkaa2) reduced GT1-7 cell AMPKα2, but not AMPKα1, activity and lowered the threshold for hypoglycaemia-induced hyperpolarisation. shAmpkα1 (also known as Prkaa1) had no effect on glucose-sensing or AMPKα2 activity. Decreased uncoupling protein 2 (Ucp2) mRNA was detected in AMPKα2-reduced cells, suggesting that AMPKα2 regulates UCP2 levels.

CONCLUSIONS/INTERPRETATION

We have demonstrated that GT1-7 cells closely mimic GE neuron glucose-sensing behaviour, and reducing AMPKα2 blunts their responsiveness to hypoglycaemic challenge, possibly by altering UCP2 activity. These results show that suppression of AMPKα2 activity inhibits normal glucose-sensing behaviour and may contribute to defective detection of hypoglycaemia.

The dynamic change of circulating tumour cells in patients with operable breast cancer before and after chemotherapy based on a multimarker QPCR platform

Background:

The possible presence of early tumour dissemination is the rationale behind the use of systemic adjuvant chemotherapy in patients with operable breast cancer. Circulating tumour cells (CTC) in peripheral blood may represent the possible presence of early tumour dissemination. However, relatively few studies were designed to investigate the relationship between the change of CTC status and the efficacy of adjuvant chemotherapy in operable breast cancer patients.

Methods:

In a prospective study, we established a multimarker real-time quantitative PCR platform to detect CTC in peripheral blood of breast cancer patients. By using this platform, we detected CTC in peripheral blood of 94 operable breast cancer patients. Control group consisted of 20 patients with benign breast disease and 20 healthy volunteers. For 72 patients who underwent systemic adjuvant chemotherapy, the dynamic CTC status at three different time points (1 day before initiation of chemotherapy, 1 week after three cycles of chemotherapy and 1 week after all cycles of chemotherapy) was observed.

Results:

Circulating tumour cells were detected in 56% (53 out of 94) of patients with operable breast cancer. The specificity was 95%. Seventy-two patients who received systemic adjuvant chemotherapy were followed up. After three cycles of chemotherapy, 47% (18 out of 38) of patients who were CTC-positive before chemotherapy changed into negative status. In addition, another 5% (2 out of 38) of patients had changed into negative status after all cycles of chemotherapy.

Conclusion:

Systemic adjuvant chemotherapy had a significant impact on CTC status, and this effect could be observed after three cycles of chemotherapy. Circulating tumour cells detection had the potential to be used to evaluate the efficacy of systemic adjuvant chemotherapy immediately after the chemotherapy was finished in operable breast cancer patients.

Preservation of (-)-epigallocatechin-3-gallate antioxidant properties loaded in heat treated β-lactoglobulin nanoparticles

(-)-Epigallocatechin-3-gallate (EGCG) was loaded in heat treated β-lactoglobulin (β-Lg) for the preservation of antioxidant activity. The effects of pH (2.5-7.0), the heating temperature of β-Lg (30-85 °C), the molar ratio of β-Lg to EGCG (1:2-1:32), and the β-Lg concentration (1-10 mg/mL) on the properties of β-Lg-EGCG complexes were studied. All four factors significantly influenced the particle size, the ζ-potential, and the entrapment efficiency of EGCG and EGCG loading in β-Lg particles. A stable and clear solution system could be obtained at pH 6.4-7.0. The highest protection of EGCG antioxidant activity was obtained with β-Lg heated at 85 °C and the molar ratio of 1:2 (β-Lg: EGCG). β-Lg-EGCG complexes were found to have the same secondary structure as native β-Lg.

Uptake of di-(2-ethylhexyl) phthalate of vegetables from plastic film greenhouses

Uptake of di-(2-ethylhexyl) phthalate (DEHP) of nine vegetables including potherb mustard, bok choy, celery, spinach, cabbage, leaf of tube, lettuce, garlic, and edible amaranth in plastic film greenhouses with different plastic films, film thickness, greenhouse age, and greenhouse height was studied. The results showed that the higher the DEHP content of film, the thicker the film, the lower the height of the greenhouse, and the younger the age of the greenhouse were, the higher the DEHP concentration of vegetables was. The results afford significant information for production of safe vegetables with low level DEHP contamination.

Preparation of the monomers of gingerols and 6-shogaol by flash high speed counter-current chromatography

The flash high speed counter-current chromatographic (FHSCCC) separation of gingerols and 6-shogaol was performed on a HSCCC instrument equipped with a 1200-ml column (5 mm tubing i.d.) at a flow rate of 25 ml/min. The performance met the FHSCCC feature that the flow rate of mobile phase (ml) is equal to or greater than the square of the diameter of the column tubing (mm). The separation employed the upper phase of stationary phase of the n-hexane-ethyl acetate-methanol-water (3:2:2:3, v/v) as the stationary phase. A stepwise elution was performed by eluting with the lower phase of n-hexane-ethyl acetate-methanol-water (3:2:2:3, v/v) for first 90 min and the lower phase of the n-hexane-ethyl acetate-methanol-water (3:2:6:5, v/v) for the second 90 min. In each separation 5 g of the ethyl acetate extract of rhizomes of ginger was loaded, yielding 1.96 g of 6-gingerol (98.3%), 0.33 g of 8-gingerol (97.8%), 0.64 g of 6-shogaol (98.8%) and 0.57 g of 10-gingerol (98.2%). The separation can be expected to scale up to industrial separation.

[Determination of active components in silymarin by UPLC-ESIMS]

A UPLC-ESIMS method was developed for simultaneous analysis of seven major bioactive flavonolignans in silymarin including silychristins A(1) and B(2), silydianin(3), silybins A(4) and B(5), and isosilybins A(6) and B(7). In this study, the seven major active flavonolignans including the diastereomers 1/2, 4/5, and 6/7 were completely separated using UPLC with an ACQUITY UPLC C18 column and MeOH-water (formic acid) mobile phase system. The collision-induced dissociation (CID) MS/MS spectra of these flavonolignans were studied systematically using ESI-MS. The results with the present methodology showed that UPLC-MS/MS can be used for general screening of active natural products from plant extracts and for the specific quality control of silymarin.

Bioactive diterpenes from Clerodendrum kaichianum

Bioassay-guided isolation studies of the extract of Clerodendrum kaichianum Hsu., a new rearranged abietane diterpene and five known diterpene compounds were isolated by various chromatography methods. Their structures were identified by means of spectroscopic methods, including 1D- and 2D-NMR spectroscopy, as (16R)-12,16-epoxy-11,14,17-trihydroxy-17(15-->16)-abeo-8,11,13-abietatrien-7-one (1), villosin A (2), salvinolone (3), 14-deoxyloleon U (4), 5,6-dehydrosugiol (5), and coleon U (6). Compounds 1, 2, 3, and 5 are reported for the first time for this genus. Compounds 1, 2, and 6 demonstrated potent cytotoxic activities against the HL-60 tumor cell line.