Temporal Structures in Positron Spectra and Charge-Sign Effects in Galactic Cosmic Rays

We present the precision measurements of 11 years of daily cosmic positron fluxes in the rigidity range from 1.00 to 41.9 GV based on 3.4×10^{6} positrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The positron fluxes show distinctly different time variations from the electron fluxes at short and long timescales. A hysteresis between the electron fluxes and the positron fluxes is observed with a significance greater than 5σ at rigidities below 8.5 GV. On the contrary, the positron fluxes and the proton fluxes show similar time variation. Remarkably, we found that positron fluxes are modulated more than proton fluxes with a significance greater than 5σ for rigidities below 7 GV. These continuous daily positron fluxes, together with AMS daily electron, proton, and helium fluxes over an 11-year solar cycle, provide unique input to the understanding of both the charge-sign and mass dependencies of cosmic rays in the heliosphere.

The default mode network is affected in the early stage of simian immunodeficiency virus infection: a longitudinal study

Acquired immune deficiency syndrome infection can lead to cognitive dysfunction represented by changes in the default mode network. Most recent studies have been cross-sectional and thus have not revealed dynamic changes in the default mode network following acquired immune deficiency syndrome infection and antiretroviral therapy. Specifically, when brain imaging data at only one time point are analyzed, determining the duration at which the default mode network is the most effective following antiretroviral therapy after the occurrence of acquired immune deficiency syndrome. However, because infection times and other factors are often uncertain, longitudinal studies cannot be conducted directly in the clinic. Therefore, in this study, we performed a longitudinal study on the dynamic changes in the default mode network over time in a rhesus monkey model of simian immunodeficiency virus infection. We found marked changes in default mode network connectivity in 11 pairs of regions of interest at baseline and 10 days and 4 weeks after virus inoculation. Significant interactions between treatment and time were observed in the default mode network connectivity of regions of interest pairs area 31/V6.R and area 8/frontal eye field (FEF). L, area 8/FEF.L and caudal temporal parietal occipital area (TPOC).R, and area 31/V6.R and TPOC.L. ART administered 4 weeks after infection not only interrupted the progress of simian immunodeficiency virus infection but also preserved brain function to a large extent. These findings suggest that the default mode network is affected in the early stage of simian immunodeficiency virus infection and that it may serve as a potential biomarker for early changes in brain function and an objective indicator for making early clinical intervention decisions.

Properties of Cosmic-Ray Sulfur and Determination of the Composition of Primary Cosmic-Ray Carbon, Neon, Magnesium, and Sulfur: Ten-Year Results from the Alpha Magnetic Spectrometer

We report the properties of primary cosmic-ray sulfur (S) in the rigidity range 2.15 GV to 3.0 TV based on 0.38×10^{6} sulfur nuclei collected by the Alpha Magnetic Spectrometer experiment (AMS). We observed that above 90 GV the rigidity dependence of the S flux is identical to the rigidity dependence of Ne-Mg-Si fluxes, which is different from the rigidity dependence of the He-C-O-Fe fluxes. We found that, similar to N, Na, and Al cosmic rays, over the entire rigidity range, the traditional primary cosmic rays S, Ne, Mg, and C all have sizeable secondary components, and the S, Ne, and Mg fluxes are well described by the weighted sum of the primary silicon flux and the secondary fluorine flux, and the C flux is well described by the weighted sum of the primary oxygen flux and the secondary boron flux. The primary and secondary contributions of the traditional primary cosmic-ray fluxes of C, Ne, Mg, and S (even Z elements) are distinctly different from the primary and secondary contributions of the N, Na, and Al (odd Z elements) fluxes. The abundance ratio at the source for S/Si is 0.167±0.006, for Ne/Si is 0.833±0.025, for Mg/Si is 0.994±0.029, and for C/O is 0.836±0.025. These values are determined independent of cosmic-ray propagation.

Temporal Structures in Electron Spectra and Charge Sign Effects in Galactic Cosmic Rays

We present the precision measurements of 11 years of daily cosmic electron fluxes in the rigidity interval from 1.00 to 41.9 GV based on 2.0×10^{8} electrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The electron fluxes exhibit variations on multiple timescales. Recurrent electron flux variations with periods of 27 days, 13.5 days, and 9 days are observed. We find that the electron fluxes show distinctly different time variations from the proton fluxes. Remarkably, a hysteresis between the electron flux and the proton flux is observed with a significance of greater than 6σ at rigidities below 8.5 GV. Furthermore, significant structures in the electron-proton hysteresis are observed corresponding to sharp structures in both fluxes. This continuous daily electron data provide unique input to the understanding of the charge sign dependence of cosmic rays over an 11-year solar cycle.

Artificial intelligence-based computer-aided diagnosis system supports diagnosis of lymph node metastasis in esophageal squamous cell carcinoma: A multicenter study

Background

This study aimed to develop an artificial intelligence-based computer-aided diagnosis system (AI-CAD) emulating the diagnostic logic of radiologists for lymph node metastasis (LNM) in esophageal squamous cell carcinoma (ESCC) patients, which contributed to clinical treatment decision-making.

Methods

A total of 689 ESCC patients with PET/CT images were enrolled from three hospitals and divided into a training cohort and two external validation cohorts. 452 CT images from three publicly available datasets were also included for pretraining the model. Anatomic information from CT images was first obtained automatically using a U-Net-based multi-organ segmentation model, and metabolic information from PET images was subsequently extracted using a gradient-based approach. AI-CAD was developed in the training cohort and externally validated in two validation cohorts.

Results

The AI-CAD achieved an accuracy of 0.744 for predicting pathological LNM in the external cohort and a good agreement with a human expert in two external validation cohorts (kappa = 0.674 and 0.587, p < 0.001). With the aid of AI-CAD, the human expert's diagnostic performance for LNM was significantly improved (accuracy [95% confidence interval]: 0.712 [0.669-0.758] vs. 0.833 [0.797-0.865], specificity [95% confidence interval]: 0.697 [0.636-0.753] vs. 0.891 [0.851-0.928]; p < 0.001) among patients underwent lymphadenectomy in the external validation cohorts.

Conclusions

The AI-CAD could aid in preoperative diagnosis of LNM in ESCC patients and thereby support clinical treatment decision-making.

Properties of Daily Helium Fluxes

We present the precision measurement of 2824 daily helium fluxes in cosmic rays from May 20, 2011 to October 29, 2019 in the rigidity interval from 1.71 to 100 GV based on 7.6×10^{8} helium nuclei collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The helium flux and the helium to proton flux ratio exhibit variations on multiple timescales. In nearly all the time intervals from 2014 to 2018, we observed recurrent helium flux variations with a period of 27 days. Shorter periods of 9 days and 13.5 days are observed in 2016. The strength of all three periodicities changes with time and rigidity. In the entire time period, we found that below ∼7  GV the helium flux exhibits larger time variations than the proton flux, and above ∼7  GV the helium to proton flux ratio is time independent. Remarkably, below 2.4 GV a hysteresis between the helium to proton flux ratio and the helium flux was observed at greater than the 7σ level. This shows that at low rigidity the modulation of the helium to proton flux ratio is different before and after the solar maximum in 2014.

[A study on the effect evaluation of virtual reality on workplace employees' emotional optimization]

Objective: To explore the effect of emotional optimization of workplace employees in immersive virtual natural environment. Methods: In July 2020, 15 subjects were selected to complete two groups of treadmill walking training experiments in virtual natural environment and daily environment respectively. At the same time, the subjects' skin electrical (EDA) , pulse frequency (Pf) , respiratory frequency (Rf) physiological data and Self-Assessment Manikin (SAM) data before and after walking were collected; the mean value of three dimensions of SAM and the emotion difference before and after the experiment were calculated. The differences of physiological indexes and subjective mood changes of subjects were tested by paired sample t-test. Results: Compared with the daily environment, the ΔEDA, ΔPf and ΔRf of the subjects in the virtual natural environment were all decreased , and the differences were statistically significant (P<0.05). There were statistically significant differences in pleasure and arousal between subjects before and after using the virtual natural environment (P <0.05). Compared with the daily environment, the Δpleasure degree of subjects using the virtual natural environment increased, and the Δarousal degree and Δdominance degree decreased, and the differences were statistically significant (P <0.05). Conclusion: Walking in virtual natural environment can help subjects improve their mood, relax and improve the regulation ability of autonomic nervous system.

Periodicities in the Daily Proton Fluxes from 2011 to 2019 Measured by the Alpha Magnetic Spectrometer on the International Space Station from 1 to 100 GV

We present the precision measurement of the daily proton fluxes in cosmic rays from May 20, 2011 to October 29, 2019 (a total of 2824 days or 114 Bartels rotations) in the rigidity interval from 1 to 100 GV based on 5.5×10^{9} protons collected with the Alpha Magnetic Spectrometer aboard the International Space Station. The proton fluxes exhibit variations on multiple timescales. From 2014 to 2018, we observed recurrent flux variations with a period of 27 days. Shorter periods of 9 days and 13.5 days are observed in 2016. The strength of all three periodicities changes with time and rigidity. The rigidity dependence of the 27-day periodicity is different from the rigidity dependences of 9-day and 13.5-day periods. Unexpectedly, the strength of 9-day and 13.5-day periodicities increases with increasing rigidities up to ∼10  GV and ∼20  GV, respectively. Then the strength of the periodicities decreases with increasing rigidity up to 100 GV.

Erratum: Properties of a New Group of Cosmic Nuclei: Results from the Alpha Magnetic Spectrometer on Sodium, Aluminum, and Nitrogen [Phys. Rev. Lett. 127, 021101 (2021)]

This corrects the article DOI: 10.1103/PhysRevLett.127.021101.

Properties of a New Group of Cosmic Nuclei: Results from the Alpha Magnetic Spectrometer on Sodium, Aluminum, and Nitrogen

We report the properties of sodium (Na) and aluminum (Al) cosmic rays in the rigidity range 2.15 GV to 3.0 TV based on 0.46 million sodium and 0.51 million aluminum nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. We found that Na and Al, together with nitrogen (N), belong to a distinct cosmic ray group. In this group, we observe that, similar to the N flux, both the Na flux and Al flux are well described by the sums of a primary cosmic ray component (proportional to the silicon flux) and a secondary cosmic ray component (proportional to the fluorine flux). The fraction of the primary component increases with rigidity for the N, Na, and Al fluxes and becomes dominant at the highest rigidities. The Na/Si and Al/Si abundance ratios at the source, 0.036±0.003 for Na/Si and 0.103±0.004 for Al/Si, are determined independent of cosmic ray propagation.

Properties of Heavy Secondary Fluorine Cosmic Rays: Results from the Alpha Magnetic Spectrometer

Precise knowledge of the charge and rigidity dependence of the secondary cosmic ray fluxes and the secondary-to-primary flux ratios is essential in the understanding of cosmic ray propagation. We report the properties of heavy secondary cosmic ray fluorine F in the rigidity R range 2.15 GV to 2.9 TV based on 0.29 million events collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The fluorine spectrum deviates from a single power law above 200 GV. The heavier secondary-to-primary F/Si flux ratio rigidity dependence is distinctly different from the lighter B/O (or B/C) rigidity dependence. In particular, above 10 GV, the F/Si/B/O ratio can be described by a power law R^{δ} with δ=0.052±0.007. This shows that the propagation properties of heavy cosmic rays, from F to Si, are different from those of light cosmic rays, from He to O, and that the secondary cosmic rays have two classes.

Properties of Iron Primary Cosmic Rays: Results from the Alpha Magnetic Spectrometer

We report the observation of new properties of primary iron (Fe) cosmic rays in the rigidity range 2.65 GV to 3.0 TV with 0.62×10^{6} iron nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. Above 80.5 GV the rigidity dependence of the cosmic ray Fe flux is identical to the rigidity dependence of the primary cosmic ray He, C, and O fluxes, with the Fe/O flux ratio being constant at 0.155±0.006. This shows that unexpectedly Fe and He, C, and O belong to the same class of primary cosmic rays which is different from the primary cosmic rays Ne, Mg, and Si class.

Properties of Neon, Magnesium, and Silicon Primary Cosmic Rays Results from the Alpha Magnetic Spectrometer

We report the observation of new properties of primary cosmic rays, neon (Ne), magnesium (Mg), and silicon (Si), measured in the rigidity range 2.15 GV to 3.0 TV with 1.8×10^{6}  Ne, 2.2×10^{6}  Mg, and 1.6×10^{6}  Si nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The Ne and Mg spectra have identical rigidity dependence above 3.65 GV. The three spectra have identical rigidity dependence above 86.5 GV, deviate from a single power law above 200 GV, and harden in an identical way. Unexpectedly, above 86.5 GV the rigidity dependence of primary cosmic rays Ne, Mg, and Si spectra is different from the rigidity dependence of primary cosmic rays He, C, and O. This shows that the Ne, Mg, and Si and He, C, and O are two different classes of primary cosmic rays.

Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of ^{3}He and ^{4}He fluxes are presented. The measurements are based on 100 million ^{4}He nuclei in the rigidity range from 2.1 to 21 GV and 18 million ^{3}He from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the ^{3}He and ^{4}He fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the ^{3}He/^{4}He flux ratio is measured for the first time. Below 4 GV, the ^{3}He/^{4}He flux ratio was found to have a significant long-term time dependence. Above 4 GV, the ^{3}He/^{4}He flux ratio was found to be time independent, and its rigidity dependence is well described by a single power law ∝R^{Δ} with Δ=-0.294±0.004. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.

Towards Understanding the Origin of Cosmic-Ray Electrons

Precision results on cosmic-ray electrons are presented in the energy range from 0.5 GeV to 1.4 TeV based on 28.1×10^{6} electrons collected by the Alpha Magnetic Spectrometer on the International Space Station. In the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. The electron flux exhibits a significant excess starting from 42.1_{-5.2}^{+5.4}  GeV compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above 25.2±1.8  GeV. Contrary to the positron flux, which has an exponential energy cutoff of 810_{-180}^{+310}  GeV, at the 5σ level the electron flux does not have an energy cutoff below 1.9 TeV. In the entire energy range the electron flux is well described by the sum of two power law components. The different behavior of the cosmic-ray electrons and positrons measured by the Alpha Magnetic Spectrometer is clear evidence that most high energy electrons originate from different sources than high energy positrons.

[Research on the influence factors of the carrying system]

Objective: To investigate surface electromyography signal (sEMG) of the major back muscle group and subjective fatigue assessment under different experimental combinations during walk with weight on both shoulders, as well as the functional status and fatigue property of human muscles. Methods: From October to December, 2017, 10 college students were recruited to participate in shoulder weight-bearing work and walk under the combinations of different shoulder strap widths, weights, and hardness of waist cushion. The subjects were required to complete 12 sets of experiments, with each set lasting for 15 minutes, and the rest time between work was 30 minutes. The sEMG signals of the upper trapezius and the erector spinae were measured during the experiment, and subjective fatigue assessment was performed during rest. The time domain evaluation index (average amplitude, aEMG) , the frequency domain evaluation index (median frequency, MF) , and the data of subjective assessment were processed and analyzed. Results: Weight and shoulder strap width had a significantly effect on fatigue (P<0.01) , and the change in the hardness of waist cushion had no significant effect on fatigue (P>0.05) . There was an interaction effect between weight and shoulder strap width (P<0.01) , and there was no interaction effect between weight, shoulder strap width, and hardness of waist cushion (P>0.05) . For the backpack carrying system, the combination of 10% weight and 50 mm shoulder strap width was the best one for relieving fatigue. The subjective test also showed that subjective feelings of muscle fatigue were associated with the weight and width, which was consistent with sEMG results. Conclusion: The results of this experiment show that the combination of 10% weight and 50 mm shoulder strap width can help to relieve muscle fatigue during walk with weight on both shoulders, and weight-bearing walking is more likely to cause the fatigue of the erector spinae.

Towards Understanding the Origin of Cosmic-Ray Positrons

Precision measurements of cosmic ray positrons are presented up to 1 TeV based on 1.9 million positrons collected by the Alpha Magnetic Spectrometer on the International Space Station. The positron flux exhibits complex energy dependence. Its distinctive properties are (a) a significant excess starting from 25.2±1.8  GeV compared to the lower-energy, power-law trend, (b) a sharp dropoff above 284_{-64}^{+91}  GeV, (c) in the entire energy range the positron flux is well described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies, and a new source term of positrons, which dominates at high energies, and (d) a finite energy cutoff of the source term of E_{s}=810_{-180}^{+310}  GeV is established with a significance of more than 4σ. These experimental data on cosmic ray positrons show that, at high energies, they predominantly originate either from dark matter annihilation or from other astrophysical sources.

Observation of Complex Time Structures in the Cosmic-Ray Electron and Positron Fluxes with the Alpha Magnetic Spectrometer on the International Space Station

We present high-statistics, precision measurements of the detailed time and energy dependence of the primary cosmic-ray electron flux and positron flux over 79 Bartels rotations from May 2011 to May 2017 in the energy range from 1 to 50 GeV. For the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. Based on 23.5×10^{6} events, we report the observation of short-term structures on the timescale of months coincident in both the electron flux and the positron flux. These structures are not visible in the e^{+}/e^{-} flux ratio. The precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over 830±30 days from one value to another. The midpoint of the transition shows an energy dependent delay relative to the reversal and changes by 260±30 days from 1 to 6 GeV.

Precision Measurement of Cosmic-Ray Nitrogen and its Primary and Secondary Components with the Alpha Magnetic Spectrometer on the International Space Station

A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV to 3.3 TV based on 2.2×10^{6} events is presented. The detailed rigidity dependence of the nitrogen flux spectral index is presented for the first time. The spectral index rapidly hardens at high rigidities and becomes identical to the spectral indices of primary He, C, and O cosmic rays above ∼700  GV. We observed that the nitrogen flux Φ_{N} can be presented as the sum of its primary component Φ_{N}^{P} and secondary component Φ_{N}^{S}, Φ_{N}=Φ_{N}^{P}+Φ_{N}^{S}, and we found Φ_{N} is well described by the weighted sum of the oxygen flux Φ_{O} (primary cosmic rays) and the boron flux Φ_{B} (secondary cosmic rays), with Φ_{N}^{P}=(0.090±0.002)×Φ_{O} and Φ_{N}^{S}=(0.62±0.02)×Φ_{B} over the entire rigidity range. This corresponds to a change of the contribution of the secondary cosmic ray component in the nitrogen flux from 70% at a few GV to <30% above 1 TV.

Observation of Fine Time Structures in the Cosmic Proton and Helium Fluxes with the Alpha Magnetic Spectrometer on the International Space Station

We present the precision measurement from May 2011 to May 2017 (79 Bartels rotations) of the proton fluxes at rigidities from 1 to 60 GV and the helium fluxes from 1.9 to 60 GV based on a total of 1×10^{9} events collected with the Alpha Magnetic Spectrometer aboard the International Space Station. This measurement is in solar cycle 24, which has the solar maximum in April 2014. We observed that, below 40 GV, the proton flux and the helium flux show nearly identical fine structures in both time and relative amplitude. The amplitudes of the flux structures decrease with increasing rigidity and vanish above 40 GV. The amplitudes of the structures are reduced during the time period, which started one year after solar maximum, when the proton and helium fluxes steadily increase. Above ∼3  GV the p/He flux ratio is time independent. We observed that below ∼3  GV the ratio has a long-term decrease coinciding with the period during which the fluxes start to rise.

Observation of New Properties of Secondary Cosmic Rays Lithium, Beryllium, and Boron by the Alpha Magnetic Spectrometer on the International Space Station

We report on the observation of new properties of secondary cosmic rays Li, Be, and B measured in the rigidity (momentum per unit charge) range 1.9 GV to 3.3 TV with a total of 5.4×10^{6} nuclei collected by AMS during the first five years of operation aboard the International Space Station. The Li and B fluxes have an identical rigidity dependence above 7 GV and all three fluxes have an identical rigidity dependence above 30 GV with the Li/Be flux ratio of 2.0±0.1. The three fluxes deviate from a single power law above 200 GV in an identical way. This behavior of secondary cosmic rays has also been observed in the AMS measurement of primary cosmic rays He, C, and O but the rigidity dependences of primary cosmic rays and of secondary cosmic rays are distinctly different. In particular, above 200 GV, the secondary cosmic rays harden more than the primary cosmic rays.

Observation of the Identical Rigidity Dependence of He, C, and O Cosmic Rays at High Rigidities by the Alpha Magnetic Spectrometer on the International Space Station

We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with 90×10^{6} helium, 8.4×10^{6} carbon, and 7.0×10^{6} oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.

Precision Measurement of the Boron to Carbon Flux Ratio in Cosmic Rays from 1.9 GV to 2.6 TV with the Alpha Magnetic Spectrometer on the International Space Station

Knowledge of the rigidity dependence of the boron to carbon flux ratio (B/C) is important in understanding the propagation of cosmic rays. The precise measurement of the B/C ratio from 1.9 GV to 2.6 TV, based on 2.3 million boron and 8.3 million carbon nuclei collected by AMS during the first 5 years of operation, is presented. The detailed variation with rigidity of the B/C spectral index is reported for the first time. The B/C ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. Remarkably, above 65 GV, the B/C ratio is well described by a single power law R^{Δ} with index Δ=-0.333±0.014(fit)±0.005(syst), in good agreement with the Kolmogorov theory of turbulence which predicts Δ=-1/3 asymptotically.

Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49×10^{5} antiproton events and 2.42×10^{9} proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ∼60 to ∼500  GV, the antiproton p[over ¯], proton p, and positron e^{+} fluxes are found to have nearly identical rigidity dependence and the electron e^{-} flux exhibits a different rigidity dependence. Below 60 GV, the (p[over ¯]/p), (p[over ¯]/e^{+}), and (p/e^{+}) flux ratios each reaches a maximum. From ∼60 to ∼500  GV, the (p[over ¯]/p), (p[over ¯]/e^{+}), and (p/e^{+}) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

Precision Measurement of the (e^{+}+e^{-}) Flux in Primary Cosmic Rays from 0.5 GeV to 1 TeV with the Alpha Magnetic Spectrometer on the International Space Station

We present a measurement of the cosmic ray (e^{+}+e^{-}) flux in the range 0.5 GeV to 1 TeV based on the analysis of 10.6 million (e^{+}+e^{-}) events collected by AMS. The statistics and the resolution of AMS provide a precision measurement of the flux. The flux is smooth and reveals new and distinct information. Above 30.2 GeV, the flux can be described by a single power law with a spectral index γ=-3.170±0.008(stat+syst)±0.008(energy scale).

Electron and positron fluxes in primary cosmic rays measured with the alpha magnetic spectrometer on the international space station

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30  GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

High statistics measurement of the positron fraction in primary cosmic rays of 0.5-500 GeV with the alpha magnetic spectrometer on the international space station

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200  GeV the positron fraction no longer exhibits an increase with energy.

First result from the Alpha Magnetic Spectrometer on the International Space Station: precision measurement of the positron fraction in primary cosmic rays of 0.5-350 GeV

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250  GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

Identification of the forensically important beetles Nicrophorus japonicus, Ptomascopus plagiatus and Silpha carinata (Coleoptera: Silphidae) based on 16S rRNA gene in China

Sarcophagous beetles play an important role in estimating postmortem interval time (PMI) in the later stages decomposition of carcasses. However, the morphological similarity of beetles usually poses a challenge for forensic scientists within their routine work. As a supplementary to traditional morphological method, molecular genetics identification is simple and time-saving. A molecular identification method involving a 288-bp segment of the 16S ribosomal RNA (16S rRNA) gene from 15 beetles of Silphidae (Coleoptera), collected from 5 locations in 4 Chinese provinces, was evaluated. Phenogram analysis of the sequenced segments by the unweighted pairgroup method analysis (UPGMA) method showed that all specimens were properly assigned into four species with strong similarity, which indicated the possibility of separation congeneric species with the short 16S rRNA fragment. These results will be instrumental for implementation of the Chinese database of forensically relevant beetles.

[Effects of IAA and stimulated microgravity on formation of adventitious roots of Chinese cabbage]

Under the induction of indole-3-acetic acid (IAA), adventitious roots were differentiated on hypocotyl segments derived from seedlings of Chinese cabbage (Brassica campestris spp. pekinensis). IAA at concentration of 0.4-1.0 mg/L in solid MS medium incited many adventitious roots on hypocotyl segments. The earliest anatomic changes were observed on cut surface of hypocotyl segments under optical microscope 24 hours after IAA treatment: cytoplasmic and nuclear density became higher in a few of parenchytmatous cells adjacent to phloem in tissue of pericycle, followed by cell divisions. Lately, the dividing cells expanded and developed into root primordium from which root cap was differentiated. After five days, most roots protruded through hypocotyl cortex and appeared just below the cut surface. The rooting capacity of the segments derived from three regions of each hypocotyl was different. High level of IAA modified the polarity of root formation on segment inserted upside down and sucrose increased the function of IAA. Additionally, microgravity did not significantly change the rooting polarity under the condition of stimulated microgravity, but it increased the competence of explants to IAA treatment. The results presented here provided an experimental system for further investigation of molecular events associated with adventitious root initiation.

Molecular characters and morphological genetics of CAL gene in Chinese cabbage

BcpCAL, the homologous gene of CAL, was isolated from Chinese cabbage. Unlike BobCAL of cauliflower, BcpCAL did not hold the terminating mutation in the fifth exon. After crosses of cauliflower with Chinese cabbage, the resultant hybrids failed to form curd, which implicates the genetic complement of BcpCAL to the mutated BobCAL in the function of curd formation. One of CAL gene isolated from the hybrid apparently comes from the female parent (Chinese cabbage) even though there are a few of the bases substituted and deleted. The result offers the molecular and genetic evidences for the study of biological function of CAL in morphological genetics of curd.

Absence of p53 gene mutations in rat colon carcinomas induced through the synergistic interaction between methylazoxymethanol and X-irradiation

p53 is one the most frequently mutated genes found in human colonic tumors. Because colonic neoplasms induced in rats by certain chemical carcinogens are similar to human colonic tumors in their histological features and proliferation characteristics, the rat has been used as an experimental model to study the pathogenesis of colon cancer. However, p53 mutations were not detected in the chemically induced colonic tumors analyzed for p53 mutations. X-irradiation has also been shown to induce colonic neoplasms in rats that resemble human colonic tumors histopathologically. Because the incidence of colonic tumors induced by methylazoxymethanol (MAM) in rats was shown to be enhanced by X-irradiation, we immunohistochemically analyzed these colonic carcinomas for the presence of p53 gene mutations. The immunohistochemical analyses clearly showed the absence of nuclear immunoreactivity in all ten tumors examined. The results from the present study indicate that point mutations in p53, at least in the coding region, are not involved in the development of colon cancer induced by the combination of MAM and X-irradiation. Our observations, together with the data from previous studies, further suggest that rat colon carcinogenesis, unlike human colon cancer, may not involve p53 mutation as an obligatory event.

A rapid dual organ rat carcinogenesis bioassay for evaluating the chemoprevention of breast and colon cancer

In this study we evaluated the effect of dietary administration of a high fat, low fiber diet (HRD) with or without 2% phytic acid (PA) on the development of mammary cancer and/or colon cancer in rats exposed to methylnitrosourea (MNU), azoxymethane (AOM) or MNU + AOM. The rats were fed a HRD alone or a HRD + 2% PA. At the end of week 2, the rats were given either a s.c. injection of MNU (50 mg/kg body wt) or one of normal saline (vehicle). At the end of weeks 3 and 4, the rats were given either a s.c. injection of AOM (15 mg/kg body wt per week) or one of normal saline (vehicle). Nine weeks after the injection of MNU or saline, 10 rats from each group were sacrificed and the mammary tumor incidence and the number of colonic aberrant crypt foci (ACF) were compared between different groups. The administration of different diets was continued for an additional 21 weeks and the mammary tumor and colon tumor incidence between different groups were compared. Results showed that rats injected with MNU alone did not develop ACF or colon tumors while those injected with AOM alone did not develop mammary tumors. Linear regression analysis of the number of ACF at 11 weeks versus colonic tumor incidence at 32 weeks, and the linear regression analysis of mammary tumor incidence at 11 weeks versus mammary tumor incidence at 32 weeks, both showed good linear correlation. These results demonstrate the potential value of the short term dual organ carcinogenesis bioassay for screening chemopreventive agents for their relative ability to inhibit the development of mammary cancer and/or colon cancer while on high risk diet.

The effect of dietary fat on the promotion of mammary and colon cancer in a dual-organ rat carcinogenesis model

Female Sprague-Dawley rats (n = 270) were randomly divided into nine subgroups (30 rats/group) and fed diets with fat contents ranging from 5% to 45% of total energy, in which fat was isocalorically substituted for carbohydrates. At Week 3, the rats were given a single injection of methylnitrosourea (MNU, 50 mg/kg body wt). At Weeks 4 and 5, rats were given an injection of azoxymethane (AOM, 15 mg/kg body wt sc). The rats were maintained on their respective experimental diets until they were sacrificed. Nine weeks after the injection of MNU, 10 rats from each group were killed and their mammary tissue was examined for tumors and their colons for aberrant crypt foci (ACF) formation. The results showed no significant increase in the number of colonic ACF or mammary tumors at 11 weeks among individual groups consuming 5-25% energy from fat or among groups consuming 30-45% energy from fat. Data analysis indicated that the effects of the two diets (5-25% energy from fat and 30-45% energy from fat) on ACF formation as well mammary tumor development were statistically different. Continuation of the diets for 32 weeks led to the development of colonic and mammary tumors. Analysis of the combined group tumor incidence data clearly showed that the colonic and mammary tumor incidence in groups fed 30-45% of energy from fat was significantly higher than that observed among groups fed 5-25% of energy from fat. Linear regression analysis of the colonic ACF at 11 weeks, colonic tumor incidence at 32 weeks, and mammary tumor incidence at 11 and 32 weeks showed good linear correlation, demonstrating the potential value of ACF and mammary tumors at 11 weeks for evaluating the carcinogenic risk associated with different diets. The main conclusion of the experiment is that the incidence of colon and mammary cancers increased rapidly when the dietary levels of fat were increased from 15% to 30% of calories and that there was no significant influence on the colon and mammary cancer risk beyond 30% of calories from fat.

Potential synergism between wheat bran and psyllium: enhanced inhibition of colon cancer

In this study we compared the influence of high fat (20% w/w) diets that combine low levels of calcium (0.18% w/w) and low (1% w/w), medium (4% w/w) and high (8% w/w) levels of dietary fiber from wheat bran (WB), with high (8% w/w) levels of dietary fiber from psyllium (PS) alone or in various combinations with WB, on the induction of colon tumors in Fischer-344 rats following exposure to azoxymethane (AOM). The rats were fed the experimental diets for 2 weeks, and then were given two s.c. injections of AOM (15 mg/kg body wt./week). Twenty-three weeks following the first injection of AOM, the incidence of colon tumors in the different dietary groups (12 rats/group) was compared. The results clearly showed that by increasing the dietary fiber concentration of WB from 1 to 8% significantly reduced the number of colon tumors/group. When the influence of 8% dietary fiber from WB on the development of colon tumors was compared with that of PS (WB:PS = 0:100), no significant difference was observed. However, combinations of WB and PS showed a greater protective effect than either WB or PS alone, at comparable levels of dietary fiber. The 50:50 combination of WB and PS showed maximum protection, while 25:75 and 75:25 combinations both produced intermediate effects. None of the diets showed any significant effect on the normal growth of rats. The results indicate that WB and PS fiber alone, and to a greater degree in combination, can offer protection against colon cancer promoted by high fat, low calcium diets. Diets that include wheat bran in combination with psyllium could be an effective means of reducing colon cancer risk in human populations addicted to high risk western diets.

Adaptative responses of tobacco callus cells to simulated microgravity by compensation

Under the rotation-induced gravity compensation, growth rate of callus was repressed by about 44%. Its osmotic and water potential declined by about 22 and 27% respectively. The content of soluble sugar was enhanced by about 123% and that of K+ by about 25%. The permeability of plasmic membrane increased and the lipid peroxidation intensified. When the callus grown under clinostatting were subcultured and returned to stationary conditions, the growth rates and related physiological indications were restored again to or near to the level of the control (SC). Electron microscopic studies showed that nuclear membrane was invaginated so deeply that some of the nuclei were like a starfish. Rough endoplasmic reticulum was diminished. The smooth one observed on the surface of slices was lengthened by almost 8.9 times of the control (SC), the longest one reached to 42 micrometers. They were often concentrated in a corner of the cell. Some of them were rolled into tube-shapes. The amyloplasts were without starch grain. It is assumed that the responses of plant cell to microgravity may be a sort of tolerable unloading reaction on endomembrane system.

Cavity-enhanced photothermal spectroscopy: dynamics, sensitivity, and spatial resolution

The spectrally resolved low-level absorption of thin films and of solid and liquid surfaces was measured by cavity-enhanced photothermal spectroscopy. The technique is ultrasensitive and can determine surfacespecific absorbances alpha(omega) ~ 10(-6) at a power density of 10(4)W/cm(2). Both cases of continuous wave and modulated laser light absorption were studied experimentally and are interpreted theoretically. It is shown that it is possible to achieve a spatial resolution of absorbance variations in the few-micrometer range. The thermal diffusivity can also be simultaneously measured by observing the time evolution of the surface temperature during laser irradiation.

The effect of high-risk and low-risk diets on aberrant crypt and colonic tumor formation in Fischer-344 rats

Eighty Fischer-344 male rats were divided into eight groups. Half the groups were given a high-risk diet (HRD) that was high in fat, low in fiber and low in calcium, while the remaining groups were given a low-risk diet (LRD) that was low in fat, high in fiber and high in calcium. After 4 weeks, four groups were then given two weekly s.c. injections of azoxymethane (AOM) (15 mg/kg body wt), and four groups were given saline injections. At the end of 6 weeks the rats were either continued on HRD, LRD, or crossed over from HRD to LRD, or LRD to HRD for an additional 6 weeks. The rats were then killed and the influence of different dietary regimens on the induction of foci of aberrant crypts (AC) in their colons was compared. The number of foci of AC was highest in the AOM-injected HRD/HRD dietary group (8.83 +/- 0.98), followed by the AOM-injected LRD/HRD group (5.37 +/- 0.75), the HRD/LRD group (3.32 +/- 0.36) and the LRD/LRD group (2.93 +/- 0.32). Except for the HRD/HRD control group, which developed a small but significant number of foci of AC (1.24 +/- 0.19), the other saline-injected dietary groups showed no significant numbers of foci of AC. Two groups of rats on HRD/HRD (AOM and saline-injected), and two groups of rats on HRD/LRD (AOM and saline-injected) were continued on HRD and LRD respectively for an additional 14 weeks. A continuous HRD in AOM-injected rats induced colon tumors in 92% of rats, while the crossover from HRD to LRD suppressed the tumor incidence to 33%. Neither diet induced any tumors in saline-injected rats. The results clearly show that the influence of HRD and LRD on the induction of foci of AC and their distribution in the colon, correlated with the induction and distribution of tumors in the colon.

Cloning and partial sequence of a cDNA for rabbit prothrombin

A 1466 base pair cDNA for rabbit prothrombin has been isolated and partially sequenced. The deduced amino acid sequence shows considerable homology with the sequences of human and bovine prothrombin. The cDNA extends from the equivalent of nucleotide 516 in the bovine sequence through the coding region and 99 nucleotides in the 3' non-coding region.

Surface absorption measurements of thin films by cavity-enhanced photothermal spectroscopy

Cavity-enhanced photothermal spectroscopy has been applied to perform ultrasensitive absorption measurements on thin metallic and high-reflectivity dielectric films. The novel method can be employed to determine minute surface-specific absorbances of alpha in the range of a few parts in 10(6) and has high sensitivity since the sample is placed inside a resonant optical cavity. Spatial-, spectral-, and time-resolved measurements were carried out. Laser surface heating calculations have been performed and can be evaluated to yield the thermal diffusivity of the thin films with a resolution at the level of a few micrometers.

Reevaluation of limited side-to-side portacaval shunt

Although the results of limited side-to-side portacaval shunt were better than those of other shunts, postoperative encephalopathy still occurred in 10.2% of the patients. To determine the relationship between the diameter of anastomotic stoma and the development of postoperative encephalopathy, animal experiments and clinical observations were carried out. In 4 of 8 dogs in 3 months after limited side-to-side portacaval shunt and in 6 patients with postoperative encephalopathy, there was significant augmentation of the diameter of anastomotic stoma. To prevent the widening of anastomotic stoma caused by blood flow under high pressure, a limiting ring of 10 mm in diameter was put around the anastomotic site during operation in 21 patients with portal hypertension. Follow-up for 3-15 months (average 6 months) showed that there was no evidence of postoperative encephalopathy and rebleeding. A ring of same kind was put around the dilated anastomotic stoma during exploration in the 6 patients, and all their cerebral symptoms and signs disappeared completely soon after the second operation.

Comparison of the effects of 4-methylhistamine on the cell-cycle response between CFU-s and its subpopulation

When bone marrow cells were treated with an H2-receptor agonist (4-methylhistamine 10(-8) M) before treatment with hydroxyurea (10(-3) M), the suicide rate of spleen colony-forming units (CFU-s) as a whole rose significantly. The rabbit antimouse brain serum (RAMBS)-resistant CFU-s subpopulation was also significantly elevated. Prior treatment of bone marrow cells with cimetidine would prevent this effect of 4-methylhistamine (4-MH). These findings not only confirm that 4-MH can trigger mouse bone marrow CFU-s to enter a DNA synthetic phase of the cell cycle, but also suggest that the RAMBS-resistant CFU-s subpopulation is more sensitive to the effect of 4-MH. Furthermore, this suggests that concentrations of the histamine receptor change during the developmental process of CFU-s.