Return-volatility correlation in financial dynamics

We investigate the return-volatility correlation both local and nonlocal in time with daily and minutely data of the German DAX and Chinese indices, and observe a leverage effect for the German DAX, while an antileverage effect for the Chinese indices. In the negative time direction, i.e., for the volatility-return correlation, an antileverage effect nonlocal in time is detected for both the German DAX and Chinese indices, although the duplicate local in time does not exist. A retarded volatility model may describe the asymmetric properties of the financial indices in the positive time direction.

Gene expression profiling of primary cultures of ovarian epithelial cells identifies novel molecular classifiers of ovarian cancer

In order to elucidate the biological variance between normal ovarian surface epithelial (NOSE) and epithelial ovarian cancer (EOC) cells, and to build a molecular classifier to discover new markers distinguishing these cells, we analysed gene expression patterns of 65 primary cultures of these tissues by oligonucleotide microarray. Unsupervised clustering highlights three subgroups of tumours: low malignant potential tumours, invasive solid tumours and tumour cells derived from ascites. We selected 18 genes with expression profiles that enable the distinction of NOSE from these three groups of EOC with 92% accuracy. Validation using an independent published data set derived from tissues or primary cultures confirmed a high accuracy (87–96%). The distinctive expression pattern of a subset of genes was validated by quantitative reverse transcription–PCR. An ovarian-specific tissue array representing tissues from NOSE and EOC samples of various subtypes and grades was used to further assess the protein expression patterns of two differentially expressed genes (Msln and BMP-2) by immunohistochemistry. This study highlights the relevance of using primary cultures of epithelial ovarian cells as a model system for gene profiling studies and demonstrates that the statistical analysis of gene expression profiling is a useful approach for selecting novel molecular tumour markers.

[Effect of magnetic mitomycin C nanoparticles on proliferation and apoptosis of L-02 cells in vitro]

OBJECTIVE

To investigate the effects of mitomycin magnetic polybutylcyanoacrylate nanoparticles (MMC-MPBCA- NP), magnetic polybutylcyanoacrylate nanoparticles (MPBCA-NP) and magnetic fluids (MF) and MMC on the proliferation and apoptosis of normal human liver cell strain (L-02 cells) in vitro.

METHODS

The effect of MMC, MMC-MPBCA-NP, MPBCA-NP, and MF on the apoptosis and cell cycle of L-02 cells was studied by flow cytometry. The changes in the cell proliferation in response to treatments of the preparations and agents were examined by MTT colorimetric assay.

RESULTS

MMC, MMC-MPBCA-NP, MPBCA-NP produced inhibition of the cell proliferation to different degrees but MF failed to result in cell proliferation inhibition. The results of MTT assay showed that MM, MPBCA-NP and MMC-MPBCA-NP all possessed concentration-dependent cytotoxicity, which increased with the concentration increment in comparison with the blank control.

CONCLUSION

The descending order of the 4 agents in their effect of L-02 cell strain growth inhibition is MF >MPBCA-NP>MMC-MPBCA-NP>MMC. MMC and MMC-MPBCA-NP can inhibit the proliferation and cause cell cycle changes of L-02 cells, while MPBCA-NP inhibits the cell proliferation without inducing cell cycle alterations.

[Determination of magnetic mitomycin C-polybutylcyanoacrylate nanoparticles in mouse plasma]

OBJECTIVE

To establish a method by high-performance liquid chromatography (HPLC) for determining the concentration of magnetic mitomycin C-polybutylcyanoacrylate nanoparticles in mouse plasma.

METHODS

Chromatography was performed on a LiChroCART C18 (250 mm x 4 mm, 5 microm) column with the mobile phase consisting of acetonitrile-NaAC (15:85), the flow rate of 1.0 ml/min, and the detection wavelength of 365 nm. Sample extraction was carried out with ethylacetate.

RESULTS

The linear range of mouse plasma mitomycin C concentration was 0.04-1.00 microg/ml, and the linear equation of Y=16 388X-17.17 (r=0.999 8) was derived.

CONCLUSION

This method is very easy to operate and suits the need of perclinical pharmacokinetic studies of mitomycin-magnetic nanoparticles and yields accurate and precise results.

[Effects of different mechanical ventilation methods on oxygenation and shunt fraction in patients undergoing valve replacement]

OBJECTIVE

To determine the effects of different mechanical ventilation on oxygenation and shunt fraction in patient undergoing valve replacement.

METHODS

Thirty ASA II-III patients (12 males, 18 females), aged 25-56 years, undergoing valve replacement were randomly divided into 3 groups according to the mechanical ventilation method. Anesthesia was induced with midazolam 0.1 mg/kg, fentanl 10 microg/kg,vecuronium 0.1 mg/kg,and etomidate 0.3 mg/kg. Valve replacement was performed with moderate hypothermic cardiopulmonary bypass( CPB). The patients were mechanically ventilated with pure oxygen and I:E ratio 1:2. Group A (TV = 7 ml/kg, f=12 bpm) ,Group B (TV=5 ml/kg, f=15 bpm), and Group C (TV=7 ml/kg, f=15 bpm). ECG, BP, SPO2, and CVP were routinely monitored. Blood samples were taken from the radial artery and pulmonary artery at 30 min after the induction of anesthesia, 10 min before CPB, and the end of operation for blood gas analysis. Respiratory index (P(A-a) DO2/PaO2), and Qs/Qt were calculated.

RESULTS

There was no significant difference in age, weight, duration of operation of CPB time and aortic cross-clamping time among the 3 groups. At the end of operation, PaO2 decreased significantly, P (A-a)DO2, RI, and Qs/Qt increased significantly in group A, while there was no significant change in group B and group C. At the end of the operation, PaCO2 was lower than the baseline value (< 35 mmHg) in Group A, but it was normal in Group B and group C.

CONCLUSION

The mechanical ventilation method of lower tidal volume and higher respiratory rate might increase the oxygenation and decrease shunt fraction and might be more suitable in patients undergoing valve replacement.

Formation and microstructural investigation of Ag–Cu alloy nanoclusters embedded in SiO2 formed by sequential ion implantation

We report on the formation of alloy nanoclusters in silica by Ag/Cu ion sequential implantation. The formation of alloy nanocluster has been evidenced by optical absorption spectra, selected area electron diffraction and energy dispersive X-ray spectra. The microstructure characters of nanoclusters have been studied by high resolution transmission electron microscopy. The lattice distortion of some nanoclusters has been observed. A model has been given to explain the distortion. Some defects (partial dislocation, stacking faults) have been found in nanoclusters.

Two-phase phenomena, minority games, and herding models

The recently discovered two-phase phenomenon in financial markets [Nature 421, 130 (2003)] is examined with the German financial index DAX, minority games, and dynamic herding models. It is observed that the two-phase phenomenon is an important characteristic of financial dynamics, independent of volatility clustering. An interacting herding model correctly produces the two-phase phenomenon.

Preparation and characterization of polybutylcyanoacrylate magnetic nanoparticles

OBJECTIVE

To Prepare and characterize polybutylcyanoacrylate (PBCA) magnetic nanoparticles.

METHODS

The suspension of PBCA magnetic nanoparticles was prepared by emulsion polymerization method. The particle size, size distribution, polydispersity and other parameters were determined by photon correlation spectroscopy and transmission electron microscopy, and the iron content in the nanoparticles by ultraviolet spectroscopy.

RESULTS

The data of the particle size and size distribution of aqueous decanoic acid stabilized Fe3O4 magnetic fluids were acquired, and the influences of concentrations of butylcyanoacrylate (BCA) and Dextran-70 on the particle size and size distribution of PBCA magnetic nanoparticles were characterized.

CONCLUSION

We have for the first time successfully prepared stable suspension of PBCA magnetic nanoparticles by emulsion polymerization method at pH 6.3-6.4 in aqueous medium.

[Using chamber technique for studying the permeability of dexamethasone sodium phosphate liposome through rabbit colon mucosa in vitro]

OBJECTIVE

To investigate the features of liposome-mediated drug permeability through the colon mucosa in vitro.

METHODS

Dexamethasone sodium phosphate liposome (DSP) was prepared using orthogonal design. With in vitro Ussing chamber experiment, the accumulated amount of DSP permeated through rabbit colon mucosa into the receptor chamber and the distribution amount in the colon were determined at different time points during the experiment.

RESULTS

Compared with the prepared DSP solution, DSP liposome decreased the permeated amount of DSP through rabbit colon mucosa. The apparent permeability coefficient (Papp, x10(-6), cm/s1) of the DSP was 31.95+/-7.65, significantly lower than that of DSP solution (88.61+/-18.61). On the other hand, the distribution amount of DSP liposome in the colon mucosa was significantly higher than that of the DSP solution both at 120 and 300 min.

CONCLUSIONS

DSP liposome dosage form may induce less toxicity with better therapeutic effect in the treatment of colitis, which is worthy of further exploitation.

Corrections to scaling in two-dimensional dynamic XY and fully frustrated XY models

With large-scale Monte Carlo simulations, we investigate the two-dimensional dynamic XY and fully frustrated XY models. Dynamic relaxation starting from a disordered or an ordered state is carefully analyzed. It is confirmed that there is a logarithmic correction to scaling for a disordered start, but a power-law correction for an ordered start. Rather accurate values of the static exponent eta and the dynamic exponent z are estimated.

Treatment of corneal epithelial in-growth after excimer laser in situ keratomileusis

OBJECTIVE

To evaluate efficacy of photo therapeutic keratectomy (PTK) on corneal epithelial growth under the lamellar flap after excimer laser in situ keratomileusis (LASIK).

METHODS

In the 6 eyes with epithelial in-growth, the corneal cap was lifted, and the in-growing epithelium was removed from the interface. Five to 10 pulses of PTK being 7 mm in diameter were placed over the undersurface of the flap and the stromal bed, irrigation between the interface and replacing corneal flap were performed, and 50 to 75 pulses PTK being 3 mm in diameter were utilized to smooth the flap edge. The follow-up period ranged from 5 to 12 months.

RESULTS

In the follow-up, no epithelial implantation reoccurred in these 6 eyes. The uncorrected visual acuity achieved their best preoperative corrected visual acuity.

CONCLUSION

The results indicate that PTK can prevent recurrent epithelial in-growth after LASIK.

Performance of AlGaN/GaN high electron mobility transistors at nanoscale gate lengths

The DC and RF performance of AlGaN/GaN high electron mobility transistors with nanoscale gate lengths is presented. The layer structures were grown by either metal organic chemical vapor deposition or rf plasma-assisted molecular beam epitaxy. Excellent scaling properties were observed as a function of both gate length and width and confirm that these devices are well suited to both high speed switching and power microwave applications.

Constrained genomic and conformational variability of the hypervariable region 1 of hepatitis C virus in chronically infected patients

We analysed the genomic and conformational variability of the hypervariable region 1 (HVR1) of the hepatitis C virus (HCV) to evaluate the importance of its biological role. A total of 865 genotype 1b HVR1 subclones were collected from serially sampled sera in 11 patients with chronic hepatitis C, four of whom received interferon therapy. Consequently, 169 distinct sequences were examined for amino acid substitutions as well as hydrophilic or hydrophobic profile at each amino acid position within HVR1. Secondary structure of HVR1 was also predicted by the method of Robson in 90 distinct sequences from eight patients, including three interferon-treated patients. Some positions within the HVR1 were invariable or nearly so as to amino acid substitution. Hydrophilic or hydrophobic residues exclusively predominated at several positions. These constrained amino acid replacement and hydrophilic or hydrophobic profiles were conserved irrespective of interferon therapy, though the frequency of amino acid replacement was greater at almost all amino acid positions within the HVR1 in interferon-treated patients. The quasispecies of HCV showed various secondary structures of HVR1, but many sequences seemed to have common characteristics. beta sheet conformations around both the N-terminus and position 20 (numbered from the NH2 terminus of E2 envelope glycoprotein), and/or coil structures around the C-terminus of HVR1 could be identified. These results suggest that HVR1 amino acid replacements are strongly constrained by a well-ordered structure, in spite of being tolerant to amino acid substitutions, and imply an important biological role of the HVR1 protein in HCV replication.

Inference and prediction of courses of the diseases caused by pathologic viruses by estimating molecular evolution of within-host virus

A new approach for inferring the evolutionary process of within-host virus is presented in this study. This approach includes a sequential-linking algorithm developed by us that can deal with the sequential viral samples that are obtained at different time points from the same host, and reconstruct a longitudinal phylogenetic tree in which the evolutionary relations between viral variants can be shown. A codon-based model, which uses a Markov process to describe substitutions between codons, is also employed in this approach to calculate synonymous and non-synonymous substitution rates and to distinguish positive selection and neutral evolution. The approach is applied to a data set of the V3 region of the HIV-1 envelope genes sequenced in different years after infection of a single patient. The results suggest that this approach may provide a more realistic description of viral evolution than the traditional evolution models because it accounts for both neutral and adaptive evolution. Most important of all, since this approach make it possible to follow up the evolutionary process of within-host virus by analyzing the sequential viral samples, it could be used in inference and prediction of the course of the diseases caused by pathologic viruses and evaluation of the treatment.

Genotype may correlate with liver carcinogenesis and tumor characteristics in cirrhotic patients infected with hepatitis B virus subtype adw

To identify the influence of hepatitis B virus (HBV) genotype on development of hepatocellular carcinoma (HCC) and clinical outcome in chronic HBV infection, 26 consecutive cirrhotic patients infected with HBV subtype adw were investigated prospectively. HBV serology was undertaken using subtype-specific antibodies against hepatitis B surface antigens. The HBV genotype was determined by sequencing directly the polymerase chain reaction products of the HBV S gene. When HCC occurred, patients underwent transcatheter arterial embolization therapy. If tumor necrosis was incomplete, additional embolization therapy was carried out after a 3- to 4-month interval. At a median follow-up of 14.1 years (range 2.2 to 31.7), HCC occurred in 9 (35%) of 26 patients. Nineteen patients were infected with genotype B and 7 with genotype C. Four of the 19 genotype B patients (21%) and 5 of the 7 genotype C patients (71%) developed HCC (P = 0.058). Patient age (<45 years or 45 < or = ) at diagnosis of cirrhosis was the only significant independent factor influencing liver carcinogenesis by multiple logistic regression analysis and Cox's regression analysis (P = 0.0069 and 0.029, respectively). When analysis was limited to the age of 45 years or more at the last visit, genotype was the only contributory factor to HCC development by univariate analysis (P = 0.038). Whereas genotype B patients responded well to embolization therapy and had no recurrence of HCC for a prolonged period of time, genotype C patients showed poor responses and died of hepatic failure due to rapid HCC progression despite embolization therapy. The cumulative incidence of survival was significantly higher in the genotype B group (P = 0.0049). The HBV genotype correlated with the development of HCC, response to embolization therapy, and recurrence of HCC. Determination of HBV genotype may be useful in predicting outcomes in HBV subtype adw-related cirrhosis.

A new algorithm for analysis of within-host HIV-1 evolution

A new algorithm for inferring the evolution of within-host viral sequences is presented. A sequential-linking approach is developed so that a longitudinal phylogenetic tree can be reconstructed from sequential molecular data that are obtained at different time points from the same host. The algorithm employs a codon-based model, which uses a Markov process to describe substitutions between codons, to calculate nonsynonymous and synonymous substitution rates and to distinguish positive selection and neutral evolution. The algorithm is applied to a data set of the V3 region of the HIV-1 envelope genes sequenced at different years after the infection of a single patient. The results suggest that this algorithm may provide a more realistic description of viral evolution than traditional evolutionary models, because it accounts for both neutral and adaptive evolution, and reconstructs a longitudinal phylogenetic tree that describes the dynamic process of viral evolution.

Once a month administration of mifepristone improves bleeding patterns in women using subdermal contraceptive implants releasing levonorgestrel

It has been suggested that the administration of an anti-progesterone might improve bleeding patterns in women with irregular bleeding while using low-dose progestin-only contraception. We report the findings of a double-blind, randomized, placebo-controlled trial of mifepristone 50 mg taken once every 4 weeks in 100 Chinese women (50 subjects and 50 controls) complaining of frequent and irregular bleeding while using a levonorgestrel-releasing subdermal contraceptive implant. In all women, regardless of treatment, the frequency of bleeding decreased significantly over 360 days of observation. Women recorded significantly shorter episodes of bleeding (P: < 0.0002) during mifepristone treatment than during the 90 days before treatment started. In contrast, the duration of bleeding episodes fell more gradually in placebo-treated controls. Women using mifepristone were more likely to find treatment acceptable than women receiving a placebo tablet (P: < 0.01). Despite concern that anti-progestogenic effects may jeopardize contraception, there were no pregnancies. This approach may offer a useful strategy to improve continuation rates by alleviating unwanted side-effects until bleeding patterns improve spontaneously with time.