Self-adjustment and disintegration threshold of Langmuir solitons in inhomogeneous plasmas.

Dynamics of Langmuir solitons in the presence of a background density gradient is investigated numerically, including cases with steep gradients to the extent the solitons can disintegrate. The disintegration threshold is explained by regarding the electric field part of the soliton as a point mass moving along the self-generated potential well corresponding to the density cavity. On the other hand, it is demonstrated that the Langmuir solitons are robust when the density gradient is below the threshold. During the acceleration phase toward low density regions, Langmuir solitons adjust themselves to balance the electric field pressure and the negative plasma pressure by expelling the imbalanced portion as density cavities at the sound velocity. When the density gradient is below the disintegration threshold, the electric field part of the soliton bounces back and forth within the potential well suggesting the solitons have internal structures.

Electron and Ion Heating Characteristics during Magnetic Reconnection in the MAST Spherical Tokamak.

Electron and ion heating characteristics during merging reconnection start-up on the MAST spherical tokamak have been revealed in detail using a 130 channel yttrium aluminum garnet (YAG) and a 300 channel Ruby-Thomson scattering system and a new 32 chord ion Doppler tomography diagnostic. Detailed 2D profile measurements of electron and ion temperature together with electron density have been achieved for the first time and it is found that electron temperature forms a highly localized hot spot at the X point and ion temperature globally increases downstream. For the push merging experiment when the guide field is more than 3 times the reconnecting field, a thick layer of a closed flux surface form by the reconnected field sustains the temperature profile for longer than the electron and ion energy relaxation time ~4-10 ms, both characteristic profiles finally forming a triple peak structure at the X point and downstream. An increase in the toroidal guide field results in a more peaked electron temperature profile at the X point, and also produces higher ion temperatures at this point, but the ion temperature profile in the downstream region is unaffected.

Electron temperature and density probe for small aeronomy satellites.

A compact and low power consumption instrument for measuring the electron density and temperature in the ionosphere has been developed by modifying the previously developed Electron Temperature Probe (ETP). A circuit block which controls frequency of the sinusoidal signal is added to the ETP so that the instrument can measure both T(e) in low frequency mode and N(e) in high frequency mode from the floating potential shift of the electrode. The floating potential shift shows a minimum at the upper hybrid resonance frequency (f(UHR)). The instrument which is named "TeNeP" can be used for tiny satellites which do not have enough conductive surface area for conventional DC Langmuir probe measurements. The instrument also eliminates the serious problems associated with the contamination of satellite surface as well as the sensor electrode.

Multichannel microwave interferometer with an antenna switching system for electron density measurement in a laboratory plasma experiment.

This study presents a simple and powerful technique for multichannel measurements of the density profile in laboratory plasmas by microwave interferometry. This technique uses electromechanical microwave switches to temporally switch the connection between multiple receiver antennas and one phase-detection circuit. Using this method, the phase information detected at different positions is rearranged into a time series that can be acquired from a minimum number of data acquisition channels (e.g., two channels in the case of quadrature detection). Our successfully developed multichannel microwave interferometer that uses the antenna switching method was applied to measure the radial electron density profiles in a magnetized plasma experiment. The advantage of the proposed method is its compactness and scalability to multidimensional measurement systems at low cost.

Electrode contamination effects of retarding potential analyzer.

The electrode contamination in electrostatic analyzers such as Langmuir probes and retarding potential analyzers (RPA) is a serious problem for space measurements. The contamination layer acts as extra capacitance and resistance and leads to distortion in the measured I-V curve, which leads to erroneous measurement results. There are two main effects of the contamination layer: one is the impedance effect and the other is the charge attachment and accumulation due to the capacitance. The impedance effect can be reduced or eliminated by choosing the proper sweeping frequency. However, for RPA the charge accumulation effect becomes serious because the capacitance of the contamination layer is much larger than that of the Langmuir probe of similar dimension. The charge accumulation on the retarding potential grid causes the effective potential, that ions experience, to be changed from the applied voltage. Then, the number of ions that can pass through the retarding potential grid to reach the collector and, thus, the measured ion current are changed. This effect causes the measured ion drift velocity and ion temperature to be changed from the actual values. The error caused by the RPA electrode contamination is expected to be significant for sounding rocket measurements with low rocket velocity (1-2 km/s) and low ion temperature of 200-300 K in the height range of 100-300 km. In this paper we discuss the effects associated with the RPA contaminated electrodes based on theoretical analysis and experiments performed in a space plasma operation chamber. Finally, the development of a contamination-free RPA for sounding rocket missions is presented.

Means to remove electrode contamination effect of Langmuir probe measurement in space.

Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.

Experimental identification of electromagnetically induced transparency in magnetized plasma.

We report the first experimental identification of the new wave branch at electron cyclotron frequency produced by the injection of a frequency-matched intense pump wave in magnetized plasma [A. G. Litvak and M. D. Tokman, Phys. Rev. Lett. 88, 095003 (2002); G. Shvets and J. S. Wurtele, Phys. Rev. Lett. 89, 115003 (2002)], which is a classical phenomenon analogous to electromagnetically induced transparency (EIT) in quantum systems. By using a frequency-sweep interferometer, we directly detected the dispersion relation of the plasma EIT branch for propagation parallel to the background magnetic field. The bandwidth of the EIT window was correlated with the pump-wave electric field and was found to agree with the theoretical prediction.

Causes of inpatient death for patients with warfare-related limb trauma and logistic regression analysis of the risk factors.

OBJECTIVES: To explore the causes and risk factors of inpatient death for patients with warfare-related limb trauma. METHODS: A retrospective study involving 339 patients with warfare-related limb trauma who were admitted to our hospital from 1998 to 2002 was conducted. Autopsy was performed for 15 cases who died in order to investigate the cause of death. Furthermore, based on the clinical features of warfare-related trauma patients, 11 factors were selected for further analysis: X1: causes of trauma, X2: shock after injury, X3: time from injury to hospital admission, X4: injured sites, X5: combined trauma (including head, thorax, abdomen, and vascular injury), X6: number of surgical procedures, X7: foreign body remaining, X8: fracture, X9: amputation, X10: duration of tourniquet homeostasis, X11: infection. All variables were available in all cases, and all parameters were quantified and fed into a computer. Multivariate statistical analysis was performed with a logistic regression model to elucidate the risk factors influencing death. RESULTS: Fifteen of the 339 inpatient cases died (4.4%). The causes were primarily acute renal failure (ARF) (seven cases, 46.7%), pulmonary embolism (PE) (three cases, 20.0%), multiple organ system failure (MOSF) (two cases, 13.3%), and gas gangrene (three cases, 20.0%). There was one case of gas gangrene with concomitant ARF, and one of gas gangrene with MOSF. The primary risk factors influencing death included shock, amputation, and complicating infection (P < 0.05). CONCLUSION: The primary cause of death from warfare-related limb trauma is ARF. The appropriate and prompt management of shock patients, the correct timing of amputation, and the prevention and correct handling of infection are important in reducing mortality.

Ion and electron heating characteristics of magnetic reconnection in a two flux loop merging experiment.

Characteristics of the high-power reconnection heating were measured for the first time directly by two-dimensional measurements of ion and electron temperatures. While electrons are heated mainly inside the current sheet by the Ohmic heating power, ions are heated mainly by fast shock or viscosity damping of the reconnection outflow in the two downstream areas. The magnetic reconnection converts the energy of reconnecting magnetic field B(p) mostly to the ion thermal energy, indicating that the reconnection heating energy is proportional to B(p)(2).

Lithium plasma emitter for collisionless magnetized plasma experiment.

This paper presents a newly developed lithium plasma emitter, which can provide quiescent and low-temperature collisionless conditions for magnetized plasma experiments. This plasma emitter generates thermal emissions of lithium ions and electrons to produce a lithium plasma. Lithium type beta-eucryptite and lanthanum-hexaboride (LaB(6)) powders were mixed and directly heated with a tungsten heater to synthesize ion and electron emissions. As a result, a plasma with a diameter of ~15 cm was obtained in a magnetic mirror configuration. The typical range of electron density was 10(12)-10(13) m(-3) and that of electron temperature was 0.1-0.8 eV with the emitter operation temperature of about 1500 K. The amplitude fluctuations for the plasma density were lower than 1%.

New interpretation of alpha-particle-driven instabilities in deuterium-tritium experiments on the Tokamak Fusion Test Reactor.

The original description of alpha particle driven instabilities in the Tokamak Fusion Test Reactor in terms of toroidal Alfvén eigenmodes (TAEs) remained inconsistent with three fundamental characteristics of the observations: (i) the variation of the mode frequency with toroidal mode number, (ii) the chirping of the mode frequency for a given toroidal mode number, and (iii) the antiballooning density perturbation of the modes. It is now shown that these characteristics can be explained by observing that cylindrical-like modes can exist in the weak magnetic shear region of the plasma that then make a transition to TAEs as the central safety factor decreases in time.

Observation of compressional Alfvén modes during neutral-beam heating on the national spherical torus experiment.

Neutral-beam-driven compressional Alfvén eigenmodes at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment. The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately 0.2omega(ci) to approximately 1.2omega(ci). The frequency has a scaling with toroidal field and plasma density consistent with Alfvén waves. The modes have been observed with high bandwidth magnetic pickup coils and with a reflectometer.

[Digital technology of X-ray radiography].

This paper introduces to you some methods to radlige the digital radiogzaphy, and there respectiae princiales and featuus.

The fertility decline in China: the contribution of changes in marital status and marital fertility.

PIP: Fertility declines in China are evident, however disagreement occurs over what the determinants are. This study examines the impact of changes in marriage patterns and marital fertility patterns in China during 1953-81. Coale's indirect standardization procedure is used, and results show wide fluctuations during 1949-64, a slight decline during 1965-68, a sharp decline during the 1970s, and a slight increase in the early 1980s. The decline in 1967 marks the beginning of the Cultural Revolution. The decline during the 1970s marks the "later, longer, fewer" campaign. Marital fertility and overall fertility follow the same curve, which suggests that marital fertility has a greater impact on fertility than nuptiality. 74.4% of total fertility during 1953-81 is accounted for by changes in marital fertility. 25.6% of total fertility is attributed to the decline in marital fertility. The proportion ever married inhibits potential fertility more during 1961-81 than during 1953-60 (30% vs. 20%). Changes in the overall fertility rate are more dramatic than changes in the index of marital fertility. For example, the decline was from 0.46 to 0.29 in general fertility compared to a decline from 0.53 to 0.41 for marital fertility. It is reasoned that marital fertility declined due to family limitation. Data are obtained from the 1982 One-Per-Thousand Sample Fertility Survey on the retrospective histories of childbearing and marriage among women aged 15-67 years. A conclusion is made that research should focus on examining the underlying determinants of marital fertility. After the 1970s a variety of factors influenced fertility including family planning policy during the 1970s and in 1979, institutional developments, and social changes in education, employment, women's status, and health services. Behavioral and psychological factors also have an impact on fertility decisions.^ieng