Charge-to-mass ratio of saltating particles in wind-blown sand.

The electrification of sand particles plays an important role in aeolian events. In this paper, the charge-to-mass ratio vertical profiles of saltating particles in wind-blown sand were measured by a field experiments. By combining the results of field measurements with our previous wind-tunnel measurements, we discussed the factors affecting the charge-to-mass ratio of saltating particles. It reveals that the magnitude of the charge-to-mass ratio increases exponentially with height above the surface. In addition, the charge polarity of saltating particles depends on the relative size between saltating and creeping particles, and the magnitude of charge-to-mass ratio is determined by wind velocity and the relative size difference ratio between saltating and creeping particles.

Electric fields in unsteady wind-blown sand.

The electrification of wind-blown sand has been widely confirmed by field and wind-tunnel measurements. It plays an important role in the lifting and transport of sand particles. In this study we investigated the behavior of electric fields in unsteady saltation by adopting periodic variation wind sequences. The influence of electric fields on sand transport rate was also discussed. The results show that both horizontal and vertical electric fields exist in unsteady saltation, and the transport rate in unsteady saltation is less than that in steady saltation. An interesting result is that the directions of vertical electric field fluctuate upward and downward-pointing with time in the unsteady saltation. This provides a possible explanation for the bipolar pattern of the vertical electric field in wind-blown sand.

Electrification of wind-blown sand: recent advances and key issues.

In this paper, we summarize the recent advances on the electrification of wind-blown sand. Some of the outstanding questions, such as the interpretation of the electrification of wind-blown sand, measurements on and models of the features of the wind-blown sand E-fields, as well as their effect on the wind-blown sand flux and electromagnetic wave propagation, are reviewed. We end by highlighting the challenges that remain.

Incident angle of saltating particles in wind-blown sand.

Incident angle of saltating particles plays a very important role in aeolian events. In this paper, the incident angles of sand particles near the sand bed were measured in wind tunnel. It reveals that the incident angles range widely from 0° to 180° and thereby the means of angles are larger than published data. Surprisingly, it is found the proportion that angles of 5°-15° occupy is far below previous reports. The measuring height is probably the most important reason for the measurement differences between this study and previous investigations.

Influence of sand grain diameter and wind velocity on lift-off velocities of sand particles.

In this paper, the velocities of sand particles near the sand bed in the saltation cloud were measured in a wind tunnel through an improved experimental scheme of the Particle Image Velocimetry (PIV) system. The influences of the diameter of sand particles in the saltation cloud and wind velocity on the probability distribution function (PDF) of lift-off velocities of sand particles were investigated. Results demonstrate that for the sand particles saltating above the sand bed with the mean grain diameter (d m = 0.3 mm), smaller and larger ones have the same velocity distribution, and wind velocity has no obvious influence on the distribution shape of the lift-off velocities, i.e., the PDFs of the horizontal and vertical lift-off velocities both follow a lognormal distribution, but the diameter of sand particles in the saltation cloud and wind velocity have an influence on the parameters of the PDF of horizontal and vertical lift-off velocities. Eventually, we present formulas to describe the PDF of lift-off velocities of sand particles with regard to the influence of wind velocity and the diameter of sand particles in the saltation cloud above the sand bed with d m = 0.3 mm.

Changes of paired-pulse evoked responses during the development of epileptic activity in the hippocampus.

Dysfunction of inhibitory synaptic transmission can destroy the balance between excitatory and inhibitory synaptic inputs in neurons, thereby inducing epileptic activity. The aim of the paper is to investigate the effects of successive excitatory inputs on the epileptic activity induced in the absence of inhibitions. Paired-pulse orthodromic and antidromic stimulations were used to test the changes in the evoked responses in the hippocampus. Picrotoxin (PTX), γ-aminobutyric acid (GABA) type A (GABA(A)) receptor antagonist, was added to block the inhibitory synaptic transmission and to establish the epileptic model. Extracellular evoked population spike (PS) was recorded in the CA1 region of the hippocampus. The results showed that the application of PTX induced a biphasic change in the paired-pulse ratio of PS amplitude. A short latency increase of the second PS (PS2) was later followed by a reappearance of PS2 depression. This type of depression was observed in both orthodromic and antidromic paired-pulse responses, whereas the GABAergic PS2 depression [called paired-pulse depression (PPD)] during baseline recordings only appeared in orthodromic-evoked responses. In addition, the depression duration at approximately 100 ms was consistent with a relative silent period observed within spontaneous burst discharges induced by prolonged application of PTX. In conclusion, the neurons may ignore the excitatory inputs and intrinsically generate bursts during epileptic activity. The depolarization block could be the mechanisms underlying the PPD in the absence of GABA(A) inhibitions. The distinct neuronal responses to stimulations during different epileptic stages may implicate the different antiepileptic effects of electrical stimulation.

CREB is a positive transcriptional regulator of gamma interferon in latent but not active tuberculosis infections.

Gamma interferon (IFN-gamma) is a crucial cytokine for protection against Mycobacterium tuberculosis, but the mechanism of IFN-gamma transcription is still unclear. The cyclic AMP (cAMP) responsive element binding (CREB) proteins belong to the bZip (basic leucine zipper) family of transcription factors and are essential for T-cell function and cytokine production. This study focused on the capacity of CREB proteins to regulate IFN-gamma transcription in CD3(+) T cells obtained from tuberculosis (TB) patients and persons with latent tuberculosis infection (LTBI) in China. The electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), and Western blotting were used to demonstrate the regulatory role of CREB. EMSA (in vitro) and ChIP (in vivo) experiments suggested CREB could bind to the IFN-gamma proximal promoter in persons with LTBI, whereas no binding was detected in TB patients. Western blotting confirmed the expression of CREB proteins, especially serine-133-phosphorylated CREB, was markedly reduced in TB patients compared with persons with LTBI. These results suggested that CREB could promote the transcription and production of IFN-gamma through binding with the IFN-gamma proximal promoter, but the regulatory role of CREB was decreased in tuberculosis patients owing to diminished expression of CREB proteins, which in turn reduced the IFN-gamma production.

[Prokaryotic expression, purification, and immunogenicity analysis of Mycobacterium tuberculosis specific excretive proteins].

OBJECTIVE: To obtain the recombinant rv1837c and rv3803c of Mycobacterium tuberculosis using gene engineering technology and explore their prokaryotic expression, purification, and immunogenicity. METHODS: The Mycobacterium tuberculosis rv1837c and rv3803c genes were amplified by polymerase chain reaction, and then cloned into the vector pTA2, followed by the subclone into the expression vector pET30a (+). The resulting plasmids, named pET30a (+): rv1837c and pET30a (+): rv3803c, encode recombinant protein containing a hexa-histidine tag on its N-terminus. pET30a (+): rv1837c and pET30a (+): rv3803c were introduced into E. coli BL21 (DE3) by transformation respectively, and the recombinant gene was induced with 0.4 mmol/L isopropyl-D-thiogalactopyranoside. The expressed products were identified by Western blot with hexa-histidine tag antibody and serum from tuberculotic patients. The histidine tagged protein was purified by nickel nitrilotriacetic acid His-Bind resin. Rabbits were immunized with purified recombinant Rv1837c and Rv3803c proteins. Then the purified recombinant Rv1837c and Rv3803c proteins were used to detect antibody in rabbit serum, which had been immunized by Western blot. RESULTS: After transformation of the E. coli and induction with 0.4 mmol/L of isopropyl-D-thiogalactopyranoside, recombinant target proteins Rv1837c (relative molecular mass: 92000) and Rv3803c (relative molecular mass: 38 000) were expressed in pET30a (+): rv1837c and pET30a (+): rv3803c system. The expressed protein existed in cytoplasm in an unsoluble form and amounted to 30% and 50% of the total proteins of E. coli. The purity of the purified protein reached 90%. The immunogenicity of the recombinant proteins Rv1837c and Rv3803c was strong, as identified by Western blot. CONCLUSION: The prokaryotic expression recombinant plasmids pET30a (+): rv1837c and pET30a (+): rv3803c was successfully constructed and the recombinant proteins Rv1837c and Rv3803c were obtained, which laid a basis for the optimized diagnosis of active tuberculosis.

Effects of carnosine on the evoked potentials in hippocampal CA1 region.

OBJECTIVE: To directly examine the effects of carnosine on neuronal excitation and inhibition in rat hippocampus in vivo. METHODS: Artificial cerebrospinal fluid with carnosine was directly administrated over the exposed rat hippocampus. The changes of neuron activity in the CA1 region of hippocampus were evaluated by orthodromically- and antidromically-evoked potentials, as well as paired-pulse stimulation paradigm. RESULTS: In both orthodromic and antidromic response potentials, carnosine transformed population spikes (PSs) with single spike into epileptiform multiple spikes. In addition, similar to the effect of (-aminobutyric acid(A) (GABA(A)) antagonist picrotoxin, carnosine decreased paired-pulse stimulating depression significantly. However, no significant change was observed in the spontaneous field potentials during the application of carnosine. CONCLUSION: The results indicate a disinhibition-induced excitation effect of carnosine on the CA1 pyramidal neurons. It provides important information against the application of carnosine as a potential anticonvulsant in clinical treatment.

[Diagnostic value of full-field digital mammography for breast carcinoma].

OBJECTIVE: To evaluate the diagnostic value of full-field digital mammography for breast cancer. METHODS: The clinical data and mammograms of 230 patients with breast diseases between January 2008 and July 2008 were collected and reviewed. Craniocaudal (CC) and mediolateral oblique (MLO) view mammograms were performed in all patients before surgery. Three experienced radiologists in breast imaging assessment analyzed and classified all the mammograms according to breast imaging reporting and data system (BI-RADS). The sensitivity, specificity and accuracy were evaluated according to their pathological diagnosis. The reasons resulting in false-negative and false-positive diagnosis were also analyzed. RESULTS: Of the 238 samples, 130 had a malignant breast tumors and 108 cases of benign breast lesions. One hundred and nine of the 130 malignant breast tumors were invasive ductal carcinoma. Fifty-seven of the 108 benign breast lesions were breast adenosis. Masses or masses with microcalcification were the most frequently seen signs of the malignant tumors, accounting for 40.8% and 20.8%, respectively. The sensitivity, specificity and accuracy of FFDM in detecting breast carcinoma were 90.8%, 87.0% and 89.1%, respectively. The false-negative signs including negative X-ray finding (5 cases) and focal asymmetric densities (4 cases). The false-positive signs were masses with spiculate, indistinctive or lobulated margin leading to misdiagnosing the lesions as malignant tumors. CONCLUSION: Full-field digital mammography (FFDM) is helpful in detection of breast cancers in women, with a higher sensitivity, specificity and accuracy, and has an important clinical application value.

Inhibition of hepatitis B virus replication by Bay 41-4109 and its association with nucleocapsid disassembly.

The authors investigate the effects and mechanisms of the anti-hepatitis B virus (HBV) agent Bay 41-4109. HepG2.2.15 cells were used to investigate the antiviral effects of Bay 41-4109 by using real-time polymerase chain reaction (PCR), western blotting, and immunofluorescence. The C terminally truncated core protein was expressed and purified. Changes in hepatitis B capsid formation were assayed by dynamic light scattering and transmission electronic microscopy. Bay 41-4109 was found to be a highly selective and potent inhibitor of hepatitis B virus replication in HepG2.2.15 cells. This compound was equally effective at inhibiting HBV DNA release and the cytoplasmic HBcAg level, with 50% inhibitory concentrations of 32.6 and 132 nM, respectively. HBV DNA and HBcAg were inhibited in a dose-dependent manner, indicating that the anti-HBV mechanisms are associated with and dependent on the rate of HBcAg inhibition. Our results indicate that Bay 41-4109 treatment disassembled the core capsids and separated them into monomers or dimers, the form in which they could be further degraded into peptides. The core protein assembled in a misdirected manner cannot function effectively. Our results suggest that, based on its particular activities, Bay 41-4109 is a promising anti-HBV candidate.

[Construction of an expression vector for high expression of siRNA].

AIM: To construct the vector for efficient expression of siRNA using pre-mir30 backbone. METHODS: By chemical synthesis method, pre-mir30 backbone introduced an appropriate restriction enzyme site for foreign shRNA inserting was cloned into an expressing vector containing U6 promoter. The silencing efficiency of a new siRNA expressing vector was detected by transfection and Western blot. RESULTS: The new vector containing pre-mir30 backbone expressing siRNA against GFP could markedly inhibit the expression of GFP compared with the vector expressing control siRNA. CONCLUSION: siRNA expressing vector constructed by pre-mir30 backbone could highly express foreign siRNA.

Induction of transient ion channel-like pores in a cancer cell by antibiotic peptide.

The anticancer activity of anti-bacterial cecropins makes them potentially useful as peptide anti-cancer drugs. We used the cell-attached patch to study the effect of cecropin B (CB; having one hydrophobic and one amphipathic alpha-helix) and its derivative, cecropin B3 (CB3; having two hydrophobic alpha-helices) on the membrane of Ags cancer cells. Application of 10-60 microM CB onto the membrane of the cancer cell produces short outward currents. Comparative study with CB3, which induces no outward currents, shows that the amphipathic group of CB is necessary for the pore formation. The results provide a rationale to study the cell-killing activity of antimicrobial peptides at the single cancer cell level.

Experimental measurement of wind-sand flux and sand transport for naturally mixed sands.

This article presents an experimental test and a program to empirically fit experimental data for the horizontal flux of wind-blown sand passing through a unit area along a vertical direction per unit time. The experimental data for the sand flow flux as a function of the height for naturally mixed sands, which were chosen from a sand dune at the southeastern edge of the Tengger desert, were measured with a sand collector in a field wind tunnel. On the basis of the experimental data and a least squares method, a fitting program is proposed here and, further, an explicit form of an empirical formula varying with height and axial wind velocity or friction velocity for the flux structure of the sands is gained. After that, we obtain an explicit form of the empirical equation for the measurement of streamwise sand transport per unit width and unit time by integrating the empirical formula for sand flux along the height direction and considering the contribution of sand creep. Finally, we evaluate the effectiveness of the predictions of some equations, especially the well-known Bagnold equation and Kawamura equation, for predicting streamwise wind-sand transport using the empirical equation obtained for mixed sands. The results show that the predictions from Bagnold's equation in the region of friction velocity u(*)>0.47 m/s and Kawamura's equation in the region u(*t)