Direct Measurement of the Spectral Structure of Cosmic-Ray Electrons+Positrons in the TeV Region with CALET on the International Space Station

Detailed measurements of the spectral structure of cosmic-ray electrons and positrons from 10.6 GeV to 7.5 TeV are presented from over 7 years of observations with the CALorimetric Electron Telescope (CALET) on the International Space Station. The instrument, consisting of a charge detector, an imaging calorimeter, and a total absorption calorimeter with a total depth of 30 radiation lengths at normal incidence and a fine shower imaging capability, is optimized to measure the all-electron spectrum well into the TeV region. Because of the excellent energy resolution (a few percent above 10 GeV) and the outstanding e/p separation (10^{5}), CALET provides optimal performance for a detailed search of structures in the energy spectrum. The analysis uses data up to the end of 2022, and the statistics of observed electron candidates has increased more than 3 times since the last publication in 2018. By adopting an updated boosted decision tree analysis, a sufficient proton rejection power up to 7.5 TeV is achieved, with a residual proton contamination less than 10%. The observed energy spectrum becomes gradually harder in the lower energy region from around 30 GeV, consistently with AMS-02, but from 300 to 600 GeV it is considerably softer than the spectra measured by DAMPE and Fermi-LAT. At high energies, the spectrum presents a sharp break around 1 TeV, with a spectral index change from -3.15 to -3.91, and a broken power law fitting the data in the energy range from 30 GeV to 4.8 TeV better than a single power law with 6.9 sigma significance, which is compatible with the DAMPE results. The break is consistent with the expected effects of radiation loss during the propagation from distant sources (except the highest energy bin). We have fitted the spectrum with a model consistent with the positron flux measured by AMS-02 below 1 TeV and interpreted the electron+positron spectrum with possible contributions from pulsars and nearby sources. Above 4.8 TeV, a possible contribution from known nearby supernova remnants, including Vela, is addressed by an event-by-event analysis providing a higher proton-rejection power than a purely statistical analysis.

Erratum: Charge-Sign Dependent Cosmic-Ray Modulation Observed with the Calorimetric Electron Telescope on the International Space Station [Phys. Rev. Lett. 130, 211001 (2023)]

This corrects the article DOI: 10.1103/PhysRevLett.130.211001.

Charge-Sign Dependent Cosmic-Ray Modulation Observed with the Calorimetric Electron Telescope on the International Space Station

We present the observation of a charge-sign dependent solar modulation of galactic cosmic rays (GCRs) with the Calorimetric Electron Telescope onboard the International Space Station over 6 yr, corresponding to the positive polarity of the solar magnetic field. The observed variation of proton count rate is consistent with the neutron monitor count rate, validating our methods for determining the proton count rate. It is observed by the Calorimetric Electron Telescope that both GCR electron and proton count rates at the same average rigidity vary in anticorrelation with the tilt angle of the heliospheric current sheet, while the amplitude of the variation is significantly larger in the electron count rate than in the proton count rate. We show that this observed charge-sign dependence is reproduced by a numerical "drift model" of the GCR transport in the heliosphere. This is a clear signature of the drift effect on the long-term solar modulation observed with a single detector.

Direct Measurement of the Cosmic-Ray Helium Spectrum from 40 GeV to 250 TeV with the Calorimetric Electron Telescope on the International Space Station

We present the results of a direct measurement of the cosmic-ray helium spectrum with the CALET instrument in operation on the International Space Station since 2015. The observation period covered by this analysis spans from October 13, 2015, to April 30, 2022 (2392 days). The very wide dynamic range of CALET allowed for the collection of helium data over a large energy interval, from ∼40  GeV to ∼250  TeV, for the first time with a single instrument in low Earth orbit. The measured spectrum shows evidence of a deviation of the flux from a single power law by more than 8σ with a progressive spectral hardening from a few hundred GeV to a few tens of TeV. This result is consistent with the data reported by space instruments including PAMELA, AMS-02, and DAMPE and balloon instruments including CREAM. At higher energy we report the onset of a softening of the helium spectrum around 30 TeV (total kinetic energy). Though affected by large uncertainties in the highest energy bins, the observation of a flux reduction turns out to be consistent with the most recent results of DAMPE. A double broken power law is found to fit simultaneously both spectral features: the hardening (at lower energy) and the softening (at higher energy). A measurement of the proton to helium flux ratio in the energy range from 60  GeV/n to about 60  TeV/n is also presented, using the CALET proton flux recently updated with higher statistics.

Cosmic-Ray Boron Flux Measured from 8.4 GeV/n to 3.8 TeV/n with the Calorimetric Electron Telescope on the International Space Station

We present the measurement of the energy dependence of the boron flux in cosmic rays and its ratio to the carbon flux in an energy interval from 8.4  GeV/n to 3.8  TeV/n based on the data collected by the Calorimetric Electron Telescope (CALET) during ∼6.4  yr of operation on the International Space Station. An update of the energy spectrum of carbon is also presented with an increase in statistics over our previous measurement. The observed boron flux shows a spectral hardening at the same transition energy E_{0}∼200  GeV/n of the C spectrum, though B and C fluxes have different energy dependences. The spectral index of the B spectrum is found to be γ=-3.047±0.024 in the interval 25<E<200  GeV/n. The B spectrum hardens by Δγ_{B}=0.25±0.12, while the best fit value for the spectral variation of C is Δγ_{C}=0.19±0.03. The B/C flux ratio is compatible with a hardening of 0.09±0.05, though a single power-law energy dependence cannot be ruled out given the current statistical uncertainties. A break in the B/C ratio energy dependence would support the recent AMS-02 observations that secondary cosmic rays exhibit a stronger hardening than primary ones. We also perform a fit to the B/C ratio with a leaky-box model of the cosmic-ray propagation in the Galaxy in order to probe a possible residual value λ_{0} of the mean escape path length λ at high energy. We find that our B/C data are compatible with a nonzero value of λ_{0}, which can be interpreted as the column density of matter that cosmic rays cross within the acceleration region.

Observation of Spectral Structures in the Flux of Cosmic-Ray Protons from 50 GeV to 60 TeV with the Calorimetric Electron Telescope on the International Space Station

A precise measurement of the cosmic-ray proton spectrum with the Calorimetric Electron Telescope (CALET) is presented in the energy interval from 50 GeV to 60 TeV, and the observation of a softening of the spectrum above 10 TeV is reported. The analysis is based on the data collected during ∼6.2  years of smooth operations aboard the International Space Station and covers a broader energy range with respect to the previous proton flux measurement by CALET, with an increase of the available statistics by a factor of ∼2.2. Above a few hundred GeV we confirm our previous observation of a progressive spectral hardening with a higher significance (more than 20 sigma). In the multi-TeV region we observe a second spectral feature with a softening around 10 TeV and a spectral index change from -2.6 to -2.9 consistently, within the errors, with the shape of the spectrum reported by DAMPE. We apply a simultaneous fit of the proton differential spectrum which well reproduces the gradual change of the spectral index encompassing the lower energy power-law regime and the two spectral features observed at higher energies.

Direct Measurement of the Nickel Spectrum in Cosmic Rays in the Energy Range from 8.8 GeV/n to 240 GeV/n with CALET on the International Space Station

The relative abundance of cosmic ray nickel nuclei with respect to iron is by far larger than for all other transiron elements; therefore it provides a favorable opportunity for a low background measurement of its spectrum. Since nickel, as well as iron, is one of the most stable nuclei, the nickel energy spectrum and its relative abundance with respect to iron provide important information to estimate the abundances at the cosmic ray source and to model the Galactic propagation of heavy nuclei. However, only a few direct measurements of cosmic-ray nickel at energy larger than ∼3  GeV/n are available at present in the literature, and they are affected by strong limitations in both energy reach and statistics. In this Letter, we present a measurement of the differential energy spectrum of nickel in the energy range from 8.8  to 240  GeV/n, carried out with unprecedented precision by the Calorimetric Electron Telescope (CALET) in operation on the International Space Station since 2015. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number Z=40). The particle's energy is measured by a homogeneous calorimeter (1.2 proton interaction lengths, 27 radiation lengths) preceded by a thin imaging section (3 radiation lengths) providing tracking and energy sampling. This Letter follows our previous measurement of the iron spectrum [1O. Adriani et al. (CALET Collaboration), Phys. Rev. Lett. 126, 241101 (2021).PRLTAO0031-900710.1103/PhysRevLett.126.241101], and it extends our investigation on the energy dependence of the spectral index of heavy elements. It reports the analysis of nickel data collected from November 2015 to May 2021 and a detailed assessment of the systematic uncertainties. In the region from 20 to 240  GeV/n our present data are compatible within the errors with a single power law with spectral index -2.51±0.07.

Gamma-Ray Observation of the Cygnus Region in the 100-TeV Energy Region

We report observations of gamma-ray emissions with energies in the 100-TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032+4127 and the other mainly with a pulsar wind nebula PWN G75.2+0.1, with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.

Measurement of the Iron Spectrum in Cosmic Rays from 10 GeV/n to 2.0 TeV/n with the Calorimetric Electron Telescope on the International Space Station

The Calorimetric Electron Telescope (CALET), in operation on the International Space Station since 2015, collected a large sample of cosmic-ray iron over a wide energy interval. In this Letter a measurement of the iron spectrum is presented in the range of kinetic energy per nucleon from 10  GeV/n to 2.0  TeV/n allowing the inclusion of iron in the list of elements studied with unprecedented precision by space-borne instruments. The measurement is based on observations carried out from January 2016 to May 2020. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number Z=40). The energy is measured by a homogeneous calorimeter with a total equivalent thickness of 1.2 proton interaction lengths preceded by a thin (3 radiation lengths) imaging section providing tracking and energy sampling. The analysis of the data and the detailed assessment of systematic uncertainties are described and results are compared with the findings of previous experiments. The observed differential spectrum is consistent within the errors with previous experiments. In the region from 50  GeV/n to 2  TeV/n our present data are compatible with a single power law with spectral index -2.60±0.03.

First Detection of sub-PeV Diffuse Gamma Rays from the Galactic Disk: Evidence for Ubiquitous Galactic Cosmic Rays beyond PeV Energies

We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of π^{0}'s produced through the interaction of protons with the interstellar medium in the Galaxy. This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk.

Direct Measurement of the Cosmic-Ray Carbon and Oxygen Spectra from 10 GeV/n to 2.2 TeV/n with the Calorimetric Electron Telescope on the International Space Station

In this paper, we present the measurement of the energy spectra of carbon and oxygen in cosmic rays based on observations with the Calorimetric Electron Telescope on the International Space Station from October 2015 to October 2019. Analysis, including the detailed assessment of systematic uncertainties, and results are reported. The energy spectra are measured in kinetic energy per nucleon from 10  GeV/n to 2.2  TeV/n with an all-calorimetric instrument with a total thickness corresponding to 1.3 nuclear interaction length. The observed carbon and oxygen fluxes show a spectral index change of ∼0.15 around 200  GeV/n established with a significance >3σ. They have the same energy dependence with a constant C/O flux ratio 0.911±0.006 above 25  GeV/n. The spectral hardening is consistent with that measured by AMS-02, but the absolute normalization of the flux is about 27% lower, though in agreement with observations from previous experiments including the PAMELA spectrometer and the calorimetric balloon-borne experiment CREAM.

First Detection of Photons with Energy beyond 100 TeV from an Astrophysical Source

We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of a muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies E>100  TeV. As a result, we observed 24 photonlike events with E>100  TeV against 5.5 background events, which corresponds to a 5.6σ statistical significance. This is the first detection of photons with E>100  TeV from an astrophysical source.

The cosmic ray energy spectrum measured with the new Tibet hybrid experiment

We have upgraded the new Tibet ASgamma experiment in China since 2014 to measure the chemical composition of cosmic rays around the knee. This hybrid experiment consist of an air-shower-core detector array (YAC-II) to detect high energy electromagnetic component, the Tibet air-shower array (Tibet-III) and a large underground water-Cherenkov muon-detector array (MD). We have carried out a detailed air-shower Monte Carlo (MC) simulation to study the performance of the hybrid detectors by using CORSIKA (version 7.5000), which includes EPOS-LHC, QGSJETII-04, SIBYLL2.1 and SIBYLL2.3 hadronic interaction models. The preliminary results of the interaction model checking above 50 TeV energy region are reported in this paper, and the primary proton and helium spectra in the energy range 50 TeV to 1015 eV was derived from YAC-I data and is smoothly connected with direct observation data at lower energies and also with our previously reported works at higher energies within statistical errors. The knee of the (P+He) spectra is located around 400 TeV. The interaction model dependence in deriving the primary (P+He) spectra is found to be small (less than 25% in absolute intensity, 10% in position of the knee), and the composition model dependence is less than 10% in absolute intensity.

Direct Measurement of the Cosmic-Ray Proton Spectrum from 50 GeV to 10 TeV with the Calorimetric Electron Telescope on the International Space Station

In this paper, we present the analysis and results of a direct measurement of the cosmic-ray proton spectrum with the CALET instrument onboard the International Space Station, including the detailed assessment of systematic uncertainties. The observation period used in this analysis is from October 13, 2015 to August 31, 2018 (1054 days). We have achieved the very wide energy range necessary to carry out measurements of the spectrum from 50 GeV to 10 TeV covering, for the first time in space, with a single instrument the whole energy interval previously investigated in most cases in separate subranges by magnetic spectrometers (BESS-TeV, PAMELA, and AMS-02) and calorimetric instruments (ATIC, CREAM, and NUCLEON). The observed spectrum is consistent with AMS-02 but extends to nearly an order of magnitude higher energy, showing a very smooth transition of the power-law spectral index from -2.81±0.03 (50-500 GeV) neglecting solar modulation effects (or -2.87±0.06 including solar modulation effects in the lower energy region) to -2.56±0.04 (1-10 TeV), thereby confirming the existence of spectral hardening and providing evidence of a deviation from a single power law by more than 3σ.

The CALorimetric Electron Telescope (CALET) on the International Space Station: Results from the First Two Years of Operation

The CALorimetric Electron Telescope (CALET) space experiment, which has been developed by Japan in collaboration with Italy and the United States, is a high-energy astroparticle physics mission on the International Space Station (ISS). The primary goals of the CALET mission include investigation of possible nearby sources of high-energy electrons, detailed study of galactic cosmic-ray acceleration and propagation, and search for dark matter signatures. With a long-term observation onboard the ISS, the CALET experiment measures the flux of cosmic-ray electrons (including positrons) up to 20 TeV, gamma-rays to 10 TeV, and nuclei up to 1,000 TeV based on its charge separation capability from Z = 1 to 40. Since the start of science operation in mid-October, 2015, a continuous observation has been maintained without any major interruptions. The number of triggered events over 10 GeV is nearly 20 million per month. By using the data obtained during the first two-years, here we present a summary of the CALET observations: 1) Electron+positron energy spectrum, 2) Nuclei analysis, 3) Gamma-ray observation with a characterization of the on-orbit performance. The search results for the electromagnetic counterparts of LIGO/Virgo gravitational wave events are also discussed.

Test of the hadronic interaction models SIBYLL2.3, EPOS-LHC and QGSJETII- 04 with Tibet EAS core data

A hybrid experiment has been started by the ASγ experiment at Yangbajing (4300m a.s.l.) in Tibet since May 2009, that consists of a high-energy air-shower-core array (YAC-I) and a high-density air-shower array (Tibet-III). In this paper, we report our results to check the hadronic interaction models SIBYLL2.3, SIBYLL2.1, EPOS-LHC and QGSJETII-04 in the multi-tens TeV energy region using YAC-I+Tibet-III experimental data from May 2009 through January 2010. The effective live time is calculated as 106.05 days. The results show that the description of transverse momentum, inelastic cross-section and inelasticity for the 4 hadronic interaction models is consistent with YAC-I experimental data within 15% systematic errors range in the forward region below 100 TeV. Among them, the EPOS-LHC model is the best hadronic interaction model. Furthermore, we find that the H4a composition model is the best one below the 100 TeV energy region.

On the Solar Cycle Variation of the Solar Diurnal Anisotropy of Multi-TeV Cosmic-ray Intensity Observed with the Tibet Air Shower Array

We analyze the temporal variation of the solar diurnal anisotropy of the multi-TeV cosmic-ray intensity observed with the Tibet air shower array from 2000 to 2009, covering the maximum and minimum of the 23rd solar cycle. We comfirm that a remarkable additional anisotropy component is superposed on the Compton-Getting anisotropy at 4.0 TeV, while its amplitude decreases at higher energy regions. In constrast to the additional anisotropy reported by the Matsushiro experiment at 0.6 TeV, we find the residual component measured by Tibet at multi-TeV energies is consistent with being stable, with a fairly constant amplitude of 0.041% ± 0.003% and a phase at around 07.17 ± 00.16 local solar time at 4.0 TeV. This suggests the additional anisotropy observed by the Tibet experiment could result from mechanisms unrelated to solar activities.

Improved outcomes of islet autotransplant after total pancreatectomy by combined blockade of IL-1β and TNFα

The efficacy of islet transplant is compromised by a significant loss of islet mass posttransplant due to an innate inflammatory reaction. We report the use of a combination of etanercept and anakinra (ANA+ETA) to block inflammatory islet damage in 100 patients undergoing total pancreatectomy with islet autotransplant. The patients were divided into 3 groups: no treatment (control [CTL]), etanercept alone (ETA), or a combination of etanercept and anakinra (ANA+ETA). Peritransplant serum samples were analyzed for protein markers of islet damage and for inflammatory cytokines. Graft function was assessed by fasting blood glucose, basal C-peptide, secretory unit of islet transplant objects (SUITO) index, and hemoglobin A_1c . Administration of both antiinflammatory drugs was well tolerated without any major adverse events. Reductions in interleukin-6, interleukin-8, and monocyte chemoattractant protein 1 were observed in patients receiving ANA+ETA compared with the CTL group, while also showing a modest improvement in islet function as assessed by basal C-peptide, glucose, hemoglobin A_1c , and SUITO index but without differences in insulin dose. These results suggest that double cytokine blockade (ANA+ETA) reduces peritransplant islet damage due to nonspecific inflammation and may represent a promising strategy to improve islet engraftment, leading to better transplant outcomes.

Extended Measurement of the Cosmic-Ray Electron and Positron Spectrum from 11 GeV to 4.8 TeV with the Calorimetric Electron Telescope on the International Space Station

Extended results on the cosmic-ray electron + positron spectrum from 11 GeV to 4.8 TeV are presented based on observations with the Calorimetric Electron Telescope (CALET) on the International Space Station utilizing the data up to November 2017. The analysis uses the full detector acceptance at high energies, approximately doubling the statistics compared to the previous result. CALET is an all-calorimetric instrument with a total thickness of 30 X_{0} at normal incidence and fine imaging capability, designed to achieve large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum in the region below 1 TeV shows good agreement with Alpha Magnetic Spectrometer (AMS-02) data. In the energy region below ∼300  GeV, CALET's spectral index is found to be consistent with the AMS-02, Fermi Large Area Telescope (Fermi-LAT), and Dark Matter Particle Explorer (DAMPE), while from 300 to 600 GeV the spectrum is significantly softer than the spectra from the latter two experiments. The absolute flux of CALET is consistent with other experiments at around a few tens of GeV. However, it is lower than those of DAMPE and Fermi-LAT with the difference increasing up to several hundred GeV. The observed energy spectrum above ∼1  TeV suggests a flux suppression consistent within the errors with the results of DAMPE, while CALET does not observe any significant evidence for a narrow spectral feature in the energy region around 1.4 TeV. Our measured all-electron flux, including statistical errors and a detailed breakdown of the systematic errors, is tabulated in the Supplemental Material in order to allow more refined spectral analyses based on our data.

Evaluation of the Interplanetary Magnetic Field Strength Using the Cosmic-Ray Shadow of the Sun

We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disk center in the "away" ("toward") interplanetary magnetic field (IMF) sector. By comparing with numerical simulations based on the solar magnetic field model, we find that the average IMF strength in the away (toward) sector is 1.54±0.21_{stat}±0.20_{syst} (1.62±0.15_{stat}±0.22_{syst}) times larger than the model prediction. These demonstrate that the observed Sun's shadow is a useful tool for the quantitative evaluation of the average solar magnetic field.

Energy Spectrum of Cosmic-Ray Electron and Positron from 10 GeV to 3 TeV Observed with the Calorimetric Electron Telescope on the International Space Station

First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on the International Space Station starting in October, 2015. Nearly a half million electron and positron events are included in the analysis. CALET is an all-calorimetric instrument with total vertical thickness of 30 X_{0} and a fine imaging capability designed to achieve a large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum over 30 GeV can be fit with a single power law with a spectral index of -3.152±0.016 (stat+syst). Possible structure observed above 100 GeV requires further investigation with increased statistics and refined data analysis.

Islet product characteristics and factors related to successful human islet transplantation from the Collaborative Islet Transplant Registry (CITR) 1999-2010

The Collaborative Islet Transplant Registry (CITR) collects data on clinical islet isolations and transplants. This retrospective report analyzed 1017 islet isolation procedures performed for 537 recipients of allogeneic clinical islet transplantation in 1999-2010. This study describes changes in donor and islet isolation variables by era and factors associated with quantity and quality of final islet products. Donor body weight and BMI increased significantly over the period (p<0.001). Islet yield measures have improved with time including islet equivalent (IEQ)/particle ratio and IEQs infused. The average dose of islets infused significantly increased in the era of 2007-2010 when compared to 1999-2002 (445.4±156.8 vs. 421.3±155.4×0(3) IEQ; p<0.05). Islet purity and total number of β cells significantly improved over the study period (p<0.01 and <0.05, respectively). Otherwise, the quality of clinical islets has remained consistently very high through this period, and differs substantially from nonclinical islets. In multivariate analysis of all recipient, donor and islet factors, and medical management factors, the only islet product characteristic that correlated with clinical outcomes was total IEQs infused. This analysis shows improvements in both quantity and some quality criteria of clinical islets produced over 1999-2010, and these parallel improvements in clinical outcomes over the same period.

An effective method to release human islets from surrounding acinar cells with agitation in high osmolality solution

INTRODUCTION

Islet purification is mainly performed by the density gradient method. However, purification of the embedded islets that are surrounded by exocrine tissue should be difficult, because their density is similar to exocrine tissue. In this study, we performed chart review to assess the relationship between the ratio of embedded islets and efficacy of purification. Then, we tested several conditions of a new method to free the islets from surrounded exocrine tissues using high osmolality solution with gentle agitation.

MATERIALS AND METHODS

First, we performed chart review of our human islet isolation. Second, embedded islet-enriched human islet fractions (embedded islets >50%) were suspended in University of Wisconsin (UW) solution (UW group, 320 mOsm/kg/H(2)0) or osmolality-adjusted UW solution (400, 500, and 600 mOsm/kg/H(2)0; 400 group, 500 group, and 600 group, respectively). Each tube was gently shaken at 4°C. The tissue samples were taken before shaking and after 15, 30, and 60 minutes. Islet yield, percentage of embedded islets, and viabilities were assessed.

RESULTS

The chart review revealed that high ratio of embedded islets deteriorated the efficacy of islet purification. The islet yield in all groups except for the 600 group did not change at 15 minutes, but it decreased in all groups at 60 minutes. The average percentage of embedded islets before shaking was 62.6%. Although percentage of embedded islets were decreasing in all groups, it was < 20% at 15 minutes in the 500 and 600 groups whereas it was >44% in the UW group, which indicated that higher osmolality would have a greater effect. Viability was >95% in all groups at 30 minutes.

CONCLUSIONS

The embedded islets deteriorated the efficacy of islet purification. Gentle agitation of embedded islets in high osmolality (500 mOsm/kg/H(2)O, 15 minutes) could release islets from surrounded exocrine tissue.

Usefulness of the secretory unit of islet transplant objects (SUITO) index for evaluation of clinical autologous islet transplantation

BACKGROUND

Assessing the engrafted islet mass is important in evaluating the efficacy of islet transplantation. We previously demonstrated that the average secretory unit of islet transplant objects (SUITO) index within 1 month of allogeneic islet transplantation was an excellent predictor of insulin independence. However, the usefulness of the SUITO index for evaluating autologous islet transplantation has not been explored. The purpose of the present study was to assess the relationship between the SUITO index and clinical outcomes after total pancreatectomy followed by autologous islet transplantation.

METHODS

We performed 27 total pancreatectomies followed by autologous islet transplantation from October 2006 to January 2011. Cases were divided into an insulin-independent group (IIG; n = 12) and an insulin-dependent group (lDG; n = 15). The SUITO index was calculated by the formula [fasting C-peptide (ng/mL)/fasting glucose (mg/dL) -63] × 1,500. The average SUITO index within the first month of transplantation except for days 0, 1, and 2, maximum SUITO index, and most recent SUITO index were calculated in each case, and values were compared between the IIG and the IDG.

RESULTS

The average SUITO index within 1 month was significantly higher in the IIG than in the IDG (24.6 ± 3.4 vs 14.9 ± 2.0, respectively; P < .02). The maximum SUITO indices were 45.7 ± 7.7 in the IIG and 30.1 ± 8.1 in the IDG (not significant), and the recent SUITO indices were 36.9 ± 6.7 in the IIG and 22.8 ± 6.1 in the IDG (not significant).

CONCLUSIONS

The average SUITO index within 1 month was an excellent predictor of insulin independence after total pancreatectomy followed by autologous islet transplantation.

Evidence for instant blood-mediated inflammatory reaction in clinical autologous islet transplantation

A nonspecific inflammatory and thrombotic reaction termed instant blood-mediated inflammatory reaction (IBMIR) has been reported when allogenic or xenogenic islets come into contact with blood. This reaction is known to cause significant loss of transplanted islets. We hypothesized that IBMIR occurs in patients undergoing total pancreatectomy followed by autologous islet transplantation (TP-AIT) and tested this hypothesis in 24 patients and in an in vitro model. Blood samples drawn during the peritransplant period showed a significant and rapid increase of thrombin-anti-thrombin III complex (TAT) and C-peptide during islet infusion, which persisted for up to 3 h, along with a decreased platelet count. A concomitant increase in levels of inflammatory proteins IL-6, IL-8 and interferon-inducible protein-10 was observed. An in vitro model composed of pure islets plus autologous blood also demonstrated significantly increased levels of TAT (p<0.05), C-peptide (p<0.05), tumor necrosis factor-alpha (p<0.05) and MCP-1 (p<0.05), as well as strong tissue factor expression in islets. Islet viability decreased significantly but was rescued by the presence of low-molecular-weight dextran sulfate. In conclusion, AIT-induced elevation of TAT and destruction of islets suggests that IBMIR might occur during AIT. Modulating this process may help improve islet engraftment and the insulin independence rate in TP-AIT patients.

Probe of the solar magnetic field using the "cosmic-ray shadow" of the sun

We report on a clear solar-cycle variation of the Sun’s shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun’s shadow, using the potential field source surface model and the current sheet source surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun’s shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun’s shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun’s shadow observed in the TeV cosmic-ray flux.

A rapid enzyme immunoassay for cholectystokinin octapeptide sulfate

A rapid and sensitive enzyme immunoassay (EIA) for cholecystokinin octapeptide sulfate (CCK-8S) has been developed. The assay is based on a double antibody method using N-terminal specific antibody to CCK-8S, and CCK-8S conjugated with horseradish peroxidase as the enzyme labeled antigen. The time for the first incubation was 2 h. The time for the second incubation, during which the first antibody was precipitated using the second antibody which contained polyethylene glycol 6000 as an accelerator of the immune reaction, was 5 min. The total assay time was less than 3 h. Intra- and interassay coefficients of variation were 4.4-5.8 and 2.7-10.97%, respectively. The minimal detectable dose was 2 pg of CCK-8S in this assay. To demonstrate the utility of this EIA, we applied this assay to evaluate changes in the levels of CCK-8S immunoreactivity in various regions of the brain after kainic acid-induced seizures in the rat. This treatment decreased the contents of CCK-8S immunoreactivity in the frontal cortex, amygdala and hippocampus. These data show that this EIA system is rapid and sensitive enough to measure changes in the tissue levels of CCK-8S.

Secretory unit of islet transplant objects (SUITO) index can predict outcome of intravenous glucose tolerance test

BACKGROUND

Simple monitoring of engrafted islet function is important for follow-up of recipients after islet transplantation. We previously developed a simple assessment tool for islet graft function; the secretory unit of islet transplant objects (SUITO) index. The aim of this study was to clarify the relationship between the SUITO index and the outcomes of intravenous glucose tolerance tests (IVGTT).

METHODS

Fifteen series of blood samples from 6 islet recipients were collected before 3, 5, 10, 20, and 30 minutes after injection of 0.5 g/kg 50% dextrose. The SUITO index was calculated using plasma C-peptide and glucose level at fasting baseline. Samples were divided into the following 3 groups; low-SUITO (SUITO index <10; n = 3); middle-SUITO (SUITO index > or =10 to <26; n = 4); and high-SUITO (SUITO index > or =26; n = 8).

RESULTS

A threshold SUITO index of 26 showed good sensitivity (85.7%) and specificity (75.0%) to predict a blood glucose level of >10 mmol/L at 30 minutes. Blood glucose levels in the low-SUITO group were significantly higher than among the other 2 groups at baseline and 10, 20 and 30 minutes (P < .05). Glucose-level areas under the receiver-operating characteristic curve during IVGTT in the low-SUITO group were also significantly larger than among the other 2 groups (P < .05).

CONCLUSION

The SUITO index, using only a fasting blood sample, predicted IVGTT outcomes.

Assessment of human islet isolation with four different collagenases

BACKGROUND

The isolation of islets from the human pancreas critically depends on the efficiency of the digestive enzymes. Liberase HI had been used as a standard preparation until the issues concerning bovine spongiform encephalopathy. Thus, we must now use other collagenases for clinical islet transplantation, four of which we have evaluated herein.

METHODS

The digestion of each of 17 pancreata from brain-dead donors was performed using the following collagenases: Liberase HI (HI; Roche, n = 9); Liberase MTF C/T (MTF; Roche, n = 4); Collagenase NB1 Premium Grade (NB1; Serva, n = 7); or Clzyme Collagenase HA (CI, VitaCyte, n = 4). Islet isolations were based on the Edmonton protocol for HI, whereas our modified islet isolation method was used for the three new enzymes (MTF, NB1, and CI).

RESULTS

There were no significant differences in donor age, body mass index, pancreas size, and cold ischemic time among the four groups. The phase I time in the NB1 group was significantly shorter than in the CI group (P = .0014). The prepurification IEQ/g in the HI group was significantly lower than the others (P = .0003 vs MTF, .0007 vs NB1, and .0009 vs CI, respectively). The postpurification IEQ/g in the MTF group was significantly higher than in the HI group (P = .006). The viability in the NB1 group was significantly greater than the HI group (P = .003).

CONCLUSION

Three new enzymes (MTF, NB1, and CI) may enable us to obtain higher islet yields than with HI.

Excellence of suito index for assessing clinical outcome of islet transplantation

BACKGROUND

Monitoring functional islet mass after transplantation is critical to follow patients. Previously we demonstrated that the average secretory unit of islet transplant objects (SUITO) index within 1 month was an excellent predictor of insulin-free status or reduction in insulin dose. In this study, we analyzed the usefulness of daily SUITO index to assess clinical outcomes.

METHODS

Five patients underwent islet transplantation, including 3 who received 2 transplantations and 2 who received a single graft. All 5 patients achieved insulin-free status with 3 remaining insulin free at the time of evaluation. We analyzed the daily relative insulin dose and SUITO index. The daily relative insulin dose was calculated as the total daily insulin dose/average pretransplant insulin dose. The SUITO index was calculated as [fasting C-peptide (ng/mL)]/[fasting blood glucose (mg/mL) - 63] x 1,500. The data analyzed based on time after islet transplantation were categorized as within or after 1 month.

RESULTS

Within 1 month after islet transplantation, there was no correlation between the daily relative insulin dose and the daily SUITO index (P = .068; R = -0.33). After 1 month, the daily relative insulin dose and the daily SUITO index were strongly correlated (P < .0001; R = -0.70). When the cutoff value of the SUITO index was decided at 26 for insulin-free status, the positive predictive value was 84.1% and negative predictive value 89.4%.

CONCLUSION

SUITO index was an excellent index to assess clinical outcomes beyond 1 month after islet transplantation.

Induction of insulin-producing cells from human pancreatic progenitor cells

INTRODUCTION

We previously established a mouse pancreatic stem cell line without genetic manipulation. In this study, we sought to identify and isolate human pancreatic stem/progenitor cells. We also tested whether growth factors and protein transduction of pancreatic and duodenal homeobox factor-1 (PDX-1) and BETA2/NeuroD into human pancreatic stem/progenitor cells induced insulin or pancreas-related gene expressions.

MATERIALS AND METHOD

Human pancreata from brain-dead donors were used for islet isolation with the standard Ricordi technique modified by the Edmonton protocol. The cells from a duct-rich population were cultured in several media, based on those designed for mouse pancreatic or for human embryonic stem cells. To induce cell differentiation, cells were cultured for 2 weeks with exendin-4, nicotinamide, keratinocyte growth factor, PDX-1 protein, or BETA2/NeuroD protein.

RESULTS

The cells in serum-free media showed morphologies similar to a mouse pancreatic stem cell line, while the cells in the medium for human embryonic stem cells formed fibroblast-like morphologies. The nucleus/cytoplasm ratios of the cells in each culture medium decreased during the culture. The cells stopped dividing after 30 days, suggesting that they had entered senescence. The cells treated with induction medium differentiated into insulin-producing cells, expressing pancreas-related genes.

CONCLUSION

Duplications of cells from a duct-rich population were limited. Induction therapy with several growth factors and transduction proteins might provide a potential new strategy for induction of transplantable insulin-producing cells.

Interaction-induced shift of the cyclotron resonance of graphene using infrared spectroscopy

We report a study of the cyclotron resonance (CR) transitions to and from the unusual n=0 Landau level (LL) in monolayer graphene. Unexpectedly, we find the CR transition energy exhibits large (up to 10%) and nonmonotonic shifts as a function of the LL filling factor, with the energy being largest at half filling of the n=0 level. The magnitude of these shifts, and their magnetic field dependence, suggests that an interaction-enhanced energy gap opens in the n=0 level at high magnetic fields. Such interaction effects normally have a limited impact on the CR due to Kohn's theorem [W. Kohn, Phys. Rev. 123, 1242 (1961)], which does not apply in graphene as a consequence of the underlying linear band structure.

Observation of an energetic radiation burst from mountain-top thunderclouds

During thunderstorms on 20 September 2008, a simultaneous detection of gamma rays and electrons was made at a mountain observatory in Japan located 2770 m above sea level. Both emissions, lasting 90 sec, were associated with thunderclouds rather than lightning. The photon spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung gamma rays arriving from a source which is 60-130 m in distance at 90% confidence level. The observed electrons are likely to be dominated by a primary population escaping from an acceleration region in the clouds.

Cyclotron resonance in bilayer graphene

We present the first measurements of cyclotron resonance of electrons and holes in bilayer graphene. In magnetic fields up to B=18 T, we observe four distinct intraband transitions in both the conduction and valence bands. The transition energies are roughly linear in B between the lowest Landau levels, whereas they follow square root[B] for the higher transitions. This highly unusual behavior represents a change from a parabolic to a linear energy dispersion. The density of states derived from our data generally agrees with the existing lowest order tight binding calculation for bilayer graphene. However, in comparing data to theory, a single set of fitting parameters fails to describe the experimental results.