Simple and active magnetic-field stabilization for cold atom experiments.

Cold atom experiments usually need a controllable and low-noise bias magnetic field to provide a quantization axis. Most labs need home-made stabilization of the field according to the actual setup, as commercially available power supply cannot directly satisfy their requirements. Here, by measuring the field fluctuations and active feedback modulating current supply of the applied magnetic field, we successfully demonstrate a field of 10.58 G with a stability to the level of 2.8 × 10-7 in a duration of 5 min. The root mean square noise is reduced to 0.05 mG, compared to the noise of 1.3 mG without stabilization. The coherence time of the magnetic-field sensitive transition between the rubidium ground states F=1,mF=-1 and 1,0, as measured by Rabi oscillation, is extended to 19.2 ms from the unstabilized value of 1.3 ms. This result is long enough for most experiments on quantum simulation and precision measurement. As our system has no passive magnetic shielding and additional compensation coils, it is highly simple and compact to provide the stable magnetic field and would be adapted to various applications with cold atoms.

State-resolved dynamics study of the H + HS reaction on the 3A' and 3A″ states with time-dependent quantum wave packet method.

The quantum dynamics calculations of the H + HS (v = 0, j = 0) reaction on the 3A' and 3A″ potential energy surfaces (PESs) are performed using the reactant coordinate based time-dependent wave packet method. State-averaged and state-resolved results for both channels of the title reaction are presented in the 0.02-1.0 eV collision energy range and compared with those carried out with quasi-classical trajectory (QCT) method. Total integral cross sections (ICSs) for both channels are in excellent agreement with previous quantum mechanical (QM)-Coriolis coupling results while poorly agree with the QCT ICSs of the exchange channel, particularly near the threshold energy region. The product rotational distributions show that for the abstraction channel, the agreement between our QM and the QCT results improves with increasing collision energy. For the exchange channel, our calculations predict colder rotational distributions as compared to those obtained by QCT calculations. Although the QM total differential cross sections (DCSs) are in qualitatively good agreement with the QCT results, the two sets of the state-to-state DCSs with several peaks exhibit great divergences. The origin of the divergences are traced by analyzing the QM DCS for the H + HS (v = 0, j = 0) → H2 (v' = 0, j' = 0) + S reaction on the 3A″ PES at Ec = 1.0 eV. It is discovered that several groups of J partial waves are involved in the reaction and the shape of the DCS is greatly altered by quantum interferences between them.

Could a traumatic epidural hematoma on early computed tomography tell us about its future development? A multi-center retrospective study in China.

Our aim for this study was to quantitatively develop an early epidural hematoma (EDH) natural evolutionary curve and assess association of the most common radiological signs of initially nonsurgical supratentorial EDHs on early computed tomography (CT), in addition to their CT time for EDH enlargement. We retrospectively reviewed pertinent data of supratentorial EDH cases with CT ≤ 6 h postinjury (1997-2013) in three medical institutions in Shanghai. Cases involved were divided into six groups according to their initial CT time postinjury (≤ 1, 1-2, 2-3, 3-4, 4-5, and 5-6 h for groups 1 through 6, respectively). Time of initial CT, EDH-associated fractures, EDH volume, and EDH locations were the focus in the present study. A total of 797 eligible cases were included. The EDH growth curve showed that EDH reached 98.1% of its final stabilized size by volume in 5 ∼ 6 h postinjury. EDH volume and locations on initial CT was greatly associated with subsequent EDH increase ≥ 30 mL with EDH increase requiring surgery when CT time was added. Multi-variate analysis succeeded in determining two risk factors for EDH enlargement ≥ 30 mL and EDH enlargement requiring an operation for EDH cases with an early CT/EDH volume >10 mL on CT performed ≤ 2 h and EDH located at the temporal or temporoparietal region on CT ≤ 1 h post brain injury. Using recursive partitioning analysis, "high-risk" identification criteria were derived to predict EDH enlargement ≥ 30 mL with sensitivity of 90.5% (95% confidence interval [CI], 77.9-96.2), specificity of 60.1% (95% CI, 54.3-65.7), and EDH enlargement requiring surgery with sensitivity of 100.0% (95% CI, 89.9-100.0), and specificity of 59.9% (95% CI, 54.1-65.4). A redo-CT 5 ∼ 6 h post impact for cases at high risk is recommended.

Quasiclassical dynamics for the H + HS abstraction and exchange reactions on the 3A" and the 3A' states.

A detailed quasiclassical trajectory study of the H + HS reaction yielding an exchange (H + HS) and an abstraction (H2 + S) channel has been performed by employing the new triplet (3)A" and (3)A' surfaces developed by our group. The cross sections for both channels are presented and found to be in good agreement with previous quantum wave packet results. The thermal rate coefficients for abstraction channel at the temperature between 200 and 1000 K have been evaluated by averaging over a Boltzmann distribution of rotational states and compared with the available experimental values. It is found that the thermal rate coefficients exhibit a conventional Arrhenius-type dependence on temperature, which agrees well with the experimental data. Average fractions, vibration and rotation distributions of the products H2 and HS at different collision energies have been also fully investigated. Furthermore, influence of the collision energy on the total and product-state-resolved differential cross sections (DCSs) for both channels are calculated and discussed. Some observations on the mechanism of the title reaction have been made; in particular it was discovered that reactive collisions along the collinear pathway cause the H2 product to scatter backward, while the reactive collisions with large impact parameters b, which are favored deviating from the minimum energy path, produced mainly forward scattering. For the exchange channel, the discrepancies in the DCS are also distinguished through an analysis of individual trajectories and found a double microscopic mechanism, migration or non-migration. The state-to-state DCSs provide a global perspective of the reaction mechanisms and their contribution to the final product internal energy states. The theoretical findings are discussed and compared with a kinematic constraint model.

Influence of collision energy and reagent rotation on the cross sections and product polarizations of the reaction F + HCl.

Quasiclassical trajectory calculations have been carried out for the F+HCl reaction in three dimensions on a recent DHSN PES of the ground 1(2)A' electronic state [M. P. Deskevich, M. Y. Hayes, K. Takahashi, R. T. Skodje, and D. J. Nesbitt, J. Chem. Phys. 124, 224303 (2006)]. The effects of the collision energy and the reagent initial rotational excitation on the cross sections and product polarization are studied for the v = 0 and j ≤ 10 states of HCl over a wide collision energy range. It has been found that either the collision energy or the HCl rotational excitation increase remarkably reaction cross sections. The QCT-calculated integral cross sections are in good agreement with previous QM results. A detailed study on product polarization for the title reaction is also performed. The calculated results show that the product rotational angular momentum j' is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The orientation of the HF product rotational angular momentum vector j' depends very sensitively on the collision energy and also affected by the reagent rotation. The theoretical findings and especially the roles of the collision energy and initial rotational momentum on the product polarization are discussed and reasonably explained by the HLH mass combination, the property of the PES, as well as the reactive mechanism.

A new rat model for diffuse axonal injury using a combination of linear acceleration and angular acceleration.

Diffuse axonal injury (DAI) is a frequent form of traumatic brain injury, and is usually associated with long-lasting neurological impairments. A new experimental model was developed in the present study to induce DAI in rats by combining low linear and angular accelerations. In most clinical scenarios, DAI is caused by these two forms of acceleration in combination. In the injury-producing facility described here, the rat rotated instantly after it had sustained the impact that produced linear acceleration. Rats rotated rapidly 90 degrees in the coronal plane at a peak angular acceleration of 137 +/- 12 krad/sec(2) with a duration of 33.7 +/- 1.2 msec. The linear acceleration was applied to the rat's head by dropping a 450 g weight from a height of 0.9 m. Rats exposed to the combined accelerations took significantly longer to regain consciousness (11.9 +/- 3.6 min) than control rats (p < 0.01) or rats subjected to purely angular or linear acceleration (p < 0.01). Although macroscopic damage was observed in all brain-injured animals, axonal damage and hemorrhagic tissue tears were only noted in the animals sustaining the combined accelerations. All rats survived the purely linear or angular acceleration, whereas the mortality rate reached 21.7% following the combined accelerations. These results show that this model is capable of reproducing the major histological and neurological changes that are associated with DAI, and that the combination of low linear and angular accelerations can produce non-linear and synergistic effects to induce moderate/severe DAI.

Sinus pericranii in the right frontal region and thrombosis.

Sinus pericranii is a rare vascular anomaly in which an abnormal communication exists between the extracranial venous system and the underlying dural venous sinus via the diploe of the skull. We describe a case of a spontaneous thrombosis of the sinus pericranii which was located in the right frontal region and presented as a focal, leathery, and noncompressible mass distinguished in character from the typical manifestation of sinus pericranii. In this case, CT, DSA, MRI, MR venography (MRV), and pathologic examination were performed. The CT showed the bone depression in the skull and the MRI demonstrated the mass, but they were not sufficiently sensitive to detect the thrombus. Pathologic examination and MRV were helpful in depicting the thrombus. She underwent a surgical resection, and at the 5-month follow-up there was no evidence of recurrence.

Giant intradiploic epidermoid cyst of the occipital bone.

Epidermoid cysts are uncommon, benign and slow-growing lesions. They often reach an enormous size without producing neurologic symptoms. We describe a 35-year-old female who had a giant intradiploic epidermoid cyst of the occipital bone. She underwent posterior cranial fossa tumor resection. Pathology confirmed epidermoid cyst. There was no recurrence at 13-month follow-up. Total removal of these cysts and repeated washing of the cavity with 0.9% saline may prevent recurrence and aseptic meningitis.

c-Met-targeted RNA interference inhibits growth and metastasis of glioma U251 cells in vitro.

Angiogenesis plays an essential role in tumor growth and metastasis and is a promising target for cancer therapy. c-Met, a receptor tyrosine kinase, and its ligand, hepatocyte growth factor (HGF), are critical in cellular proliferation, motility, invasion, and angiogenesis. The present study was designed to determine the role of c-Met in growth and metastasis of glioma U251 cells using RNA interference (RNAi) technology in vitro. We constructed three kinds of shRNA expression vectors aiming at the c-Met gene, then transfected them into glioma U251 cells by lipofectamine(TM) 2000. The level of c-Met mRNA was investigated by real-time polymerse chain reaction (RT-PCR). The protein expression of c-Met was observed by immunofluoresence staining and western blotting. U251 cell growth and adherence was detected by methyl thiazole tetrazolium assay. The apoptosis of U251 cells was examined with a flow cytometer. The adherence, invasion, and in vitro angiogenesis assays of U251 cells were done. We got three kinds of c-Met specific shRNA expression vectors which could efficiently inhibit the growth and metastasis of U251 cells and the expression of c-Met in U251 cells. RT-PCR, immunofluoresence staining and western blotting showed that inhibition rate for c-Met expression was up to 90%, 79% and 85%, respectively. The expression of c-Met can be inhibited by RNA interference in U251 cells, which can inhibit the growth and metastasis of U251 cell and induce cell apoptosis. These results indicate that RNAi of c-Met can be an effective antiangiogenic strategy for glioma.