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The generation of a plasma with an ultrahigh energy density of 1.2 GJ/cm3 (which corresponds to about 12 Gbar pressure) is investigated by irradiating thin stainless-steel foils with high-contrast femtosecond laser pulses with relativistic intensities of up to 1022 W/cm2. The plasma parameters are determined by X-ray spectroscopy. The results show that most of the laser energy is absorbed by the plasma at solid density, indicating that no pre-plasma is generated in the current experimental setup.

Background: Postoperative scoliosis is often seen after hemipelvectomy for malignancies involving the pelvic area, but the details remain unclear. The objectives were to investigate the development patterns and risk factors of scoliosis after hemipelvectomy. Methods: We retrospectively reviewed 30 patients who underwent hemipelvectomy at our hospital between 1998 and 2020. The risk factors of scoliosis with a Cobb angle of ≥10° were investigated. Results: The postoperative Cobb angle significantly increased in all patients compared with the preoperative one (p < 0.001), and the change ratio of the Cobb angle was significantly higher during the first postoperative year than thereafter. The external hemipelvectomy (EH) group demonstrated a larger Cobb angle and a higher change ratio than the internal hemipelvectomy group. Nine patients developed scoliosis with a final Cobb angle of ≥10°, and the risk factors were EH (p = 0.017), P1+2+3+4 resection according to the Enneking classification (p = 0.005), iliac crest resection (p = 0.004), L5/S resection (p = 0.020), and no pelvic ring reconstruction after hemipelvectomy (p = 0.004). Conclusions: Approximately 30% of patients who underwent hemipelvectomy developed scoliosis with a Cobb angle of ≥10°, and this angle increased rapidly during the first postoperative year. Hence, careful follow-up of scoliosis is required after hemipelvectomy.

Aims: The risk of postoperative complications after resection of soft-tissue sarcoma in the medial thigh is higher than in other locations. This study investigated whether a vessel sealing system (VSS) could help reduce the risk of postoperative complications after wide resection of soft-tissue sarcoma in the medial thigh. Methods: Of 285 patients who underwent wide resection for soft-tissue sarcoma between 2014 and 2021 at our institution, 78 patients with tumours in the medial thigh were extracted from our database. Information on clinicopathological characteristics, preoperative treatment, surgical treatment (use of VSS, blood loss volume, operating time), and postoperative course (complications, postoperative haemoglobin changes, total drainage volume, and drainage and hospitalization durations) were obtained from medical records. We statistically compared clinical outcomes between patients whose surgery did or did not use VSS (VSS and non-VSS groups, respectively). Results: There were 24 patients in the VSS group and 54 in the non-VSS group. There were no significant differences between the two groups in terms of clinicopathological background. The total drainage volume in the VSS group was significantly less than that in the non-VSS group (1,176 ml vs 3,114 ml; p = 0.018). Moreover, the drainage and hospitalization durations were significantly shorter in the VSS group compared to the non-VSS group (p = 0.017 and p = 0.024, respectively). Conclusion: Our results suggest that use of VSS can help reduce the risk of postoperative complications after wide resection of soft-tissue sarcoma in the medial thigh. Cite this article: Bone Jt Open 2023;4(6):442–446.

Background:. The proximal humerus is a common site for both primary and metastatic bone tumors. Although various methods have been developed for reconstruction following resection of the proximal humerus, a consensus on which technique is best has not been established. We focused on the sling procedure using a free vascularized fibular graft (FVFG) and conducted what we believe to be the largest retrospective study of patients to undergo this surgery to date. Methods:. We retrospectively reviewed the data of 19 patients who underwent the sling procedure with use of an FVFG at our hospital between 1998 and 2022. The median age was 20 years, and the median follow-up duration was 63.1 months. Surgical data, oncological outcomes, the postoperative course, complications, and functional outcomes as measured with use of the Musculoskeletal Tumor Society (MSTS) score were thoroughly reviewed. Results:. The median operative duration was 555 minutes, and the median blood loss was 374 mL. The median length of the bone defect was 17.0 cm, and the median length of the graft was 20.0 cm. With respect to oncological outcomes, 9 patients were continuously disease-free, 9 patients had no evidence of disease, and 1 patient was alive with disease. Bone union was present in 13 of the 17 patients for whom it was evaluable. The median time to bone union was 4 months. Graft growth was observed in 2 pediatric patients. Postoperative fracture was a major complication at the recipient site. The incidence of pseudarthrosis significantly increased when the FVFG could not be inserted into the remaining humeral bone or was split in half (p = 0.002). Although a few patients demonstrated peroneal nerve palsy at the donor site, the symptom was temporary. The overall functional outcome was favorable, with an average MSTS score of 66.9%. Conclusions:. The sling procedure demonstrated a low complication rate and a favorable functional outcome overall. Therefore, we believe that this procedure is a useful reconstruction method for patients in a broad age range who have a wide defect of the proximal humerus. Level of Evidence:. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Abstract Multi-MeV high-purity proton acceleration by using a hydrogen cluster target irradiated with repetitive, relativistic intensity laser pulses has been demonstrated. Statistical analysis of hundreds of data sets highlights the existence of markedly high energy protons produced from the laser-irradiated clusters with micron-scale diameters. The spatial distribution of the accelerated protons is found to be anisotropic, where the higher energy protons are preferentially accelerated along the laser propagation direction due to the relativistic effect. These features are supported by three-dimensional (3D) particle-in-cell (PIC) simulations, which show that directional, higher energy protons are generated via the anisotropic ambipolar expansion of the micron-scale clusters. The number of protons accelerating along the laser propagation direction is found to be as high as 1.6 $$\pm \,{0.3}$$ ± 0.3 $$\times$$ × 10 $$^9$$ 9 /MeV/sr/shot with an energy of 2.8 $$\pm \,{1.9}$$ ± 1.9 MeV, indicating that laser-driven proton acceleration using the micron-scale hydrogen clusters is promising as a compact, repetitive, multi-MeV high-purity proton source for various applications.

The generation of highly charged ions in laser plasmas is usually associated with collisional ionization processes that occur in electron–ion collisions. An alternative ionization channel caused by tunnel ionization in an optical field is also capable of effectively producing highly charged ions with ionization potentials of several kiloelectronvolts when the laser intensity q > 1020 W/cm2. It is challenging to clearly distinguish the impacts of the optical field and collisional ionizations on the evolution of the charge state of a nonequilibrium plasma produced by the interaction of high-intensity, ultrashort PW-class laser pulses with dense matter. In the present work, it is shown that the answer to this question can be obtained in some cases by observing the X-ray spectral lines caused by the transition of an electron into the K-shell of highly charged ions. The time-dependent calculations of plasma kinetics show that this is possible, for example, if sufficiently small clusters targets with low-density background gas are irradiated. In the case of Ar plasma, the limit of the cluster radius was estimated to be R0 = 0.1 μm. The calculation results for argon ions were compared with the results of the experiment at the J-KAREN-P laser facility at QST-KPSI.

We described the output performance and temporal quality enhancement of the J-KAREN-P petawatt laser facility. After wavefront correction using a deformable mirror, focusing with an f/1.3 off-axis parabolic mirror delivered a peak intensity of 1022 W/cm2 at 0.3 PW power levels. Technologies to improve the temporal contrast were investigated and tested. The origins of pre-pulses generated by post-pulses were identified and the elimination of most pre-pulses by removal of the post-pulses with wedged optics was achieved. A cascaded femtosecond optical parametric amplifier based on the utilization of the idler pulse rather than the signal pulse was developed for the complete elimination of the remaining pre-pulses. The orders of magnitude enhancement of the pedestal before the main pulse were obtained by using a higher surface quality of the convex mirror in the Öffner stretcher. A single plasma mirror was installed in the J-KAREN-P laser beam line for further contrast improvement of three orders of magnitude. The above developments indicate, although it has not been directly measured, the contrast can be as high as approximately 1015 up to 40 ps before the main pulse. We also showed an overview of the digital transformation (DX) of the system, enabling remote and automated operation of the J-KAREN-P laser facility.

Limb-salvage surgery for pelvic sarcomas remains one of the most challenging surgical procedures for musculoskeletal oncologists. In the past several decades, various surgical techniques have been developed for periacetabular reconstruction following pelvic tumor resection. These methods include endoprosthetic reconstruction, allograft or autograft reconstruction, arthrodesis, and hip transposition. Each of these procedures has its own advantages and disadvantages, and there is no consensus or gold standard for periacetabular reconstruction. Consequently, this review provides an overview of the clinical outcomes for each of these reconstructive options following pelvic tumor resections. Overall, high complication rates are associated with the use of massive implants/grafts, and deep infection is generally the most common cause of reconstruction failure. Functional outcomes decline with the occurrence of severe complications. Further efforts to avoid complications using innovative techniques, such as antibiotic-laden devices, computer navigation, custom cutting jigs, and reduced use of implants/grafts, are crucial to improve outcomes, especially in patients at a high risk of complications.

Abstract Background The use of nomograms for prognostication of individual cancer patients has been recommended in order to facilitate precision medicine. However, models for patients with soft tissue sarcomas (STSs) are limited because of the rarity and heterogeneity of such cancers. In addition, no model has been developed on the basis of an Asian cohort. Here, we attempted to develop and internally validate nomograms for patients with localized STSs of the trunk and extremity. Methods This study retrospectively extracted 2827 patients with primary trunk and extremity STSs after definitive surgery using the Bone and Soft Tissue Tumor Registry, which is a nationwide sarcoma database in Japan. We developed three nomograms predicting the probability of local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS) and disease-specific survival (DSS) at 2 years after surgery, using the Cox multivariate model. The nomograms were internally validated for discrimination and calibration using bootstrap resampling and assessed for their clinical applicability by decision curve analysis (DCA). Results Local recurrence, distant metastasis and disease-specific death occurred in 241 patients (8.5%), 554 patients (19.6%) and 230 patients (8.1%), respectively. Histological diagnosis, grade and tumor size strongly influenced all three endpoints. The nomograms predicted accurately the probability of LRFS, DMFS and DSS (concordance index: 0.73, 0.70 and 0.75, respectively). DCA demonstrated that our nomograms had clinical applicability. Conclusion We have developed the first nomograms for STSs based on an Asian cohort. These nomograms allowed accurate prediction of LRFS, DMFS and DSS at 2 years after definitive surgery, and can be used as a guide by clinicians for appropriate follow-up and counseling of patients.

Soft tissue sarcoma (STS) of the extremities is typically treated with limb-sparing surgery and radiation therapy; with this treatment approach, high local control rates can be achieved. However, postradiation bone fractures, fractures occurring in the prior radiation field with minimal or no trauma, are a serious late complication that occurs in 2–22% of patients who receive surgery and radiation for STS. Multiple risk factors for sustaining a postradiation fracture exist, including high radiation dose, female sex, periosteal stripping, older age, femur location, and chemotherapy administration. The treatment of these pathological fractures can be difficult, with complications including delayed union, nonunion, and infection posing particular challenges. Here, we review the mechanisms, risk factors, and treatment challenges associated with postradiation fractures in STS patients.

PurposeThe survival impact of geographic access to specialized care remains unknown in patients with soft-tissue sarcomas (STS). This study aimed to clarify the association between the patient travel distance and survival outcome and investigate the factors lying behind it.MethodsA total of 34 528 patients with STS registered in the National Cancer Data Base, diagnosed from 2004-2016, were investigated.ResultsTumor stage correlated with travel distance: patients with metastatic disease stayed closer to home. However, the type of facility showed greatest variation: 37.0%, 51.0%, 73.5%, and 75.9% of patients with ≤10 miles, 10.1-50 miles, 50.1-100 miles, and >100 miles, respectively (P100 miles: HR = 0.877; P = 0.001) and management at academic/research (versus non-academic/research) centers (HR = 0.857; P100 miles) to an academic/research center, with a 26.9% survival benefit (HR = 0.731; PConclusionsThis national study demonstrated that increased travel distance was associated with superior survival, attributable to a higher proportion of patients receiving sarcoma care at distant academic/research centers. These data support centralized care for STS. Overcoming referral and travel barriers may enable more patients to be treated at specialized centers and may further improve survival rates for patients with STS, even when it imposes an increased travel burden.

Abstract Background There have been fewer improvements in the clinical outcomes of adolescent and young adult (AYA) patients with cancer than for children and older adults, possibly because fewer studies focus on patients in this age group. The aims of this study were (1) to determine survival rates of bone sarcoma among AYAs in Japan (for comparison with other age groups), and (2) to establish whether belonging to the AYA age group at diagnosis was correlated with poor cancer survival in Japan. Methods A total of 3457 patients diagnosed with bone sarcoma (1930 male and 1527 female) were identified from 63,931 records in the Bone and Soft Tissue Tumor (BSTT) registry, a nationwide Japanese database, from 2006 to 2013. The histologic subtypes of bone sarcoma were osteosarcoma, chondrosarcoma, and Ewing sarcoma. The primary endpoints for prognosis were the occurrence of tumor-related death. We compared the epidemiological features of AYAs with other age groups. The cancer survival rates were calculated using the Kaplan-Meier method. Cox proportional hazards models were used to analyze the prognostic factors for cancer survival. Results The majority of AYA had osteosarcoma 631 (56.2%), while 198 (17.6%) had chondrosarcoma. The frequency of bone sarcoma occurrence was highest among AYA patients, who accounted for a marked proportion of patients with each type of sarcoma. With the exception of sarcoma type, AYA patients did not significantly differ from patients in other age groups for any of the investigated clinicopathological parameters. Cancer survival of AYA patients was significantly higher than in the elderly. Univariate and multivariate analyses revealed that AYA status was not a predictor of poor cancer survival. However, older age (≥65 years) was a predictor of poor cancer survival in patients with overall bone sarcoma, osteosarcoma, chondrosarcoma. Conclusion This epidemiological study is the first to investigate AYA patients with bone sarcoma using the nationwide BSTT Registry. We found that cancer survival of AYA patients was significantly higher than that of the elderly. AYA status was not a predictor of poor cancer survival in Japan.

Myxofibrosarcoma occurs in adults and is associated with high local relapse. Here, based on exome/transcriptome sequencing and DNA methylation analysis, the authors identify driver genes and methylation clusters associated with unique combinations of mutations, outcomes, and immune cell compositions.

Abstract Background Few reports have described clinical features, prognosis and prognostic factors of osteosarcoma patients according to age. Methods Using the Bone and Soft Tissue Tumor Registry in Japan, we identified 1043 osteosarcoma patients including 760 who were younger than 40 years, 173 aged between 41 and 64 years, and 110 patients older than 65 years. We extracted data on patient demographics and prognosis. Prognostic factors for patients older than 65 years or other age groups were analyzed. Results Patients older than 65 years showed a significantly higher proportion of tumors arising in the trunk and with metastasis at diagnosis, and their 5-year disease-specific survival (DSS) rate was 32.7%. Multivariate analysis showed that the presence of metastasis at diagnosis [hazard ratio (HR): 3.04; 95% confidence interval (CI), 1.63–5.69; P 16 cm in size (HR: 2.84 compared with

Ultra-high intensity femtosecond lasers have now become excellent scientific tools for the study of extreme material states in small-scale laboratory settings. The invention of chirped-pulse amplification (CPA) combined with titanium-doped sapphire (Ti:sapphire) crystals have enabled realization of such lasers. The pursuit of ultra-high intensity science and applications is driving worldwide development of new capabilities. A petawatt (PW = 1015 W), femtosecond (fs = 10−15 s), repetitive (0.1 Hz), high beam quality J-KAREN-P (Japan Kansai Advanced Relativistic ENgineering Petawatt) Ti:sapphire CPA laser has been recently constructed and used for accelerating charged particles (ions and electrons) and generating coherent and incoherent ultra-short-pulse, high-energy photon (X-ray) radiation. Ultra-high intensities of 1022 W/cm2 with high temporal contrast of 10−12 and a minimal number of pre-pulses on target has been demonstrated with the J-KAREN-P laser. Here, worldwide ultra-high intensity laser development is summarized, the output performance and spatiotemporal quality improvement of the J-KAREN-P laser are described, and some experimental results are briefly introduced.

The oncologic risk of ionizing radiation is widely known. Sarcomas developing after radiotherapy have been reported, and they are a growing problem because rapid advancements in cancer management and screening have increased the number of long-term survivors. Although many patients have undergone radiation treatment in Asian countries, scarce reports on post-radiation sarcomas (PRSs) have been published. We investigated the feature and prognostic factors of PRSs in an Asian population. The Eastern Asian Musculoskeletal Oncology Group participated in this project. Cases obtained from 10 centers were retrospectively reviewed. Patients with genetic malignancy predisposition syndrome, or who had more than one type of malignancy before the development of secondary sarcoma were excluded. Forty-two high-grade sarcomas among a total of 43 PRSs were analyzed. There were 29 females and 13 males, with a median age of 58.5 years; 23 patients had bone tumors and 19 had soft tissue tumors. The most common primary lesion was breast cancer. The median latency period was 192 months. There were no differences in radiation dose, latency time, and survival rates between bone and soft tissue PRSs. The most common site and diagnosis were the pelvic area and osteosarcoma and malignant fibrous histiocytoma for bone and soft tissue PRSs. The median follow-up period was 25.5 months. Five-year metastasis-free and overall survival rates were 14.5% and 16.6%, and 39.1% and 49.6% for bone and soft tissue PRSs. Survival differences depending on initial metastasis and surgery were significant in soft tissue sarcomas. Although this study failed to find ethnic differences, it is the largest review on PRS in an Asian population. As early recognition through long-term surveillance is a key to optimal management, clinicians should take efforts to understand the real status of PRS.

This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a peak power of 600 TW. We also describe applications of the laser system in the relativistically dominant regime of laser-matter interactions and discuss a compact, high efficiency diode-pumped laser system.

We discuss requirements on relativistic-irradiance (I0 > 1018 W/cm2) high-power (multi-terawatt) ultrashort (femtosecond) lasers for efficient generation of high-order harmonics in gas jet targets in a new regime discovered recently (Pirozhkov et al., 2012). Here, we present the results of several experimental campaigns performed with different irradiances, analyse the obtained results and derive the required laser parameters. In particular, we found that the root mean square (RMS) wavefront error should be smaller than ~100 nm (~λ/8). Further, the angular dispersion should be kept considerably smaller than the diffraction divergence, i.e., μrad level for 100–300-mm beam diameters. The corresponding angular chirp should not exceed 10−2 μrad/nm for a 40-nm bandwidth. We show the status of the J-KAREN-P laser (Kiriyama et al., 2015; Pirozhkov et al., 2017) and report on the progress towards satisfying these requirements.

The functional and oncologic results of eighteen patients with primary malignant periacetabular tumors were reviewed to determine the impact of surgical treatment. The reconstruction procedures were endoprosthesis (11), hip transposition (4), iliofemoral arthrodesis (2), and frozen bone autograft (1). After a mean follow-up of 62 months, 13 patients were alive and 5 had died of their disease; the 5-year overall survival rate was 67.2%. The corresponding mean MSTS scores of patients with endoprosthesis (11) and other reconstructions (7) were 42% and 55% (49%, 68%, and 50%), respectively. Overall, postoperative complications including deep infection or dislocation markedly worsened the functional outcome. Iliofemoral arthrodesis provided better function than the other procedures, whereas endoprosthetic reconstruction demonstrated poor functional outcome except for patients who were reconstructed with the adequate soft tissue coverage. Avoiding postoperative complications is highly important for achieving better function, suggesting that surgical procedures with adequate soft tissue coverage or without the massive use of nonbiological materials are preferable. Appropriate selection of the reconstructive procedures for individual patients, considering the amount of remaining bone and soft tissues, would lead to better clinical outcomes.

Hibernoma is a rare benign lipogenic tumor of brown fat that develops in a wide variety of locations. Although the features of hibernoma demonstrated by MRI resemble those of liposarcoma, recent FDG-PET/CT studies have documented higher radiotracer uptake than liposarcoma, suggesting that FDG/PET/CT is useful for differentiating hibernoma from liposarcoma. Here we report two cases of hibernoma that showed relatively lower SUVs than those reported previously, lying within the range for liposarcoma. Our findings emphasize that hibernoma needs to be included in the differential diagnosis of any fat-containing tumor showing intense accumulation by FDG-PET/CT. Although it is unlikely that such a rare condition could be reasonably diagnosed on the basis of MRI and FDG-PET/CT alone due to possible SUV overlap between hibernoma and liposarcoma, it is important to recognize this extremely rare lipogenic tumor for accurate diagnosis and appropriate management.

Introduction. Although several intercalary reconstructions after resection of a lower extremity malignant bone tumor are reported, there are no optimal methods which can provide a long-term reconstruction with fewest complications. We present the outcome of reconstruction using a devitalized autograft and a vascularized fibula graft composite. Materials and Methods. We conducted a retrospective review of 11 patients (7 males, 4 females; median age 27 years) undergoing reconstruction using a devitalized autograft (pasteurization (n=6), deep freezing (n=5)) and a vascularized fibula graft composite for lower extremity malignant bone tumors (femur (n=10), tibia (n=1)). Results. The mean period required for callus formation and bone union was 4.4 months and 9.9 months, respectively. Four postoperative complications occurred in 3 patients: 2 infections (1 pasteurized autograft, 1 frozen autograft) and 1 fracture and 1 implant failure (both in pasteurized autografts). Graft removal was required in 2 patients with infections. The mean MSTS score was 81% at last follow-up. Conclusions. Although some complications were noted in early cases involving a pasteurized autograft, our novel method involving a combination of a frozen autograft with a vascularized fibula graft and rigid fixation with a locking plate may offer better outcomes than previously reported allografts or devitalized autografts.

Background. Alveolar soft part sarcoma (ASPS) is a rare tumor, and little information is available regarding its clinical features and appropriate treatments. Methods. A retrospective review of 26 consecutive ASPS patients (12 male, 14 female; mean age of 27 years) treated at our institution over 30 years (mean followup; 71 months) was performed. Results. The primary tumor developed in the lower extremity (12), trunk (8), and upper extremity (6), with an average size of 7.2 cm (range, 2–14 cm). The AJCC stage at presentation was IIA (7), III (3), and IV (16). Surgical excision was performed in 20 patients (R0 18, R1 plus radiotherapy 2) without local recurrence. Six patients (stage IIA 3/7, stage III 3/3) later developed metastases after an average period of 28.7 months. The median survival of the 26 patients was 90 months, with overall 5/10-year survival rates of 64%/48%. AJCC stage and tumor size were significant prognostic factors. Significant palliation and slowing of metastasis progression were achieved with gamma knife radiotherapy. Nine patients receiving chemotherapy showed no objective response. Conclusions. ASPS is indolent but has a high propensity for metastasis. Early diagnosis and complete excision of the small primary tumor are essential in the treatment of ASPS.

A new regime of relativistic high-order harmonic generation has been discovered (Pirozhkov 2012 Phys . Rev . Lett . http://dx.doi.org/10.1103/PhysRevLett.108.135004 108 http://dx.doi.org/10.1103/PhysRevLett.108.135004 ). Multi-terawatt relativistic-irradiance (>10 ^18 W cm ^−2 ) femtosecond (∼30–50 fs) lasers focused to underdense (few × 10 ^19 cm ^−3 ) plasma formed in gas jet targets produce comb-like spectra with hundreds of even and odd harmonic orders reaching the photon energy of 360 eV, including the ‘water window’ spectral range. Harmonics are generated either by linearly or circularly polarized pulses from the J-KAREN (KPSI, JAEA) and Astra Gemini (CLF, RAL, UK) lasers. The photon number scalability has been demonstrated with a 120 TW laser, producing 40 μ J sr ^−1 per harmonic at 120 eV. The experimental results are explained using particle-in-cell simulations and catastrophe theory. A new mechanism of harmonic generation by sharp, structurally stable, oscillating electron spikes at the joint of the boundaries of the wake and bow waves excited by a laser pulse is introduced. In this paper, detailed descriptions of the experiments, simulations and model are provided and new features are shown, including data obtained with a two-channel spectrograph, harmonic generation by circularly polarized laser pulses and angular distribution.

The dynamics of a MeV laser-produced proton beam affected by a radio frequency (rf) electric field has been studied. The proton beam was emitted normal to the rear surface of a thin polyimide target irradiated with an ultrashort pulsed laser with a power density of 4×10^{18} W/cm^{2}. The energy spread was compressed to less than 11% at the full width at half maximum (FWHM) by an rf field. Focusing and defocusing effects of the transverse direction were also observed. These effects were analyzed and reproduced by Monte Carlo simulations. The simulation results show that the transversely focused protons had a broad continuous spectrum, while the peaks in the proton spectrum were defocused. Based on this new information, we propose that elimination of the continuous energy component of laser-produced protons is possible by utilizing a focal length difference between the continuous spectral protons and the protons included in the spectral peak.

This report briefly summarizes preliminary results of the Monte Carlo calculations in order to simulate the propagation of the hard solar X-rays in the atmosphere. The simulated results were compared quantitatively with the data of the hard solar X-ray event of February 11,1970, which was observed simultaneously at balloon and satellite altitudes. According to these comparisons, the results simulated from the satellite data are well consistent with the balloon data at the time of peak intensity, but show higher fluxes by factor of 7 at maximum in the decaying phase of the event about 1 minute before the sunset for the satellite. These suggest that the satellite-borne X-ray detector recorded a considerable amount of atmospheric scattered photons with primary solar X-rays at a time just before the sunset.

Cosmic ray helium flux at the energy around 100 MeV/N was measured by four balloon flights in the summer during the period from 1970 to 1972 at Syowa Station, Antarctica, with the aid of scintillation counter telescopes. The observed helium intensity of 1972 at the energy of 100 MeV/N showed about 100% increase over that of 1970. This value seems to be consistent with the estimated values from the data obtained by Mt. Washington neutron monitor, balloons and satellites in other years. Also the absolute intensity of the present data seems to be 20-30 % higher than the value extrapolated from the data obtained by LEZNIAK and WEBBER in 1965-1968.

The 10th Japanese Antarctic Research Expedition carried out the following observations during the period of 1968-1970. The latitude dependence of cosmic-ray intensities was observed aboard the icebreaker FUJI along her route from Japan to Syowa Station, Antarctica, in 1968-1969. This latitude survey was made for three components, i. e., cosmic-ray neutron, meson and total ionizing components. For a month from January 14, 1969, simultaneous balloon observations of the geomagnetic conjugacy of auroral X-rays were attempted at Syowa Station and Keflavik, Iceland. Only three of ten Syowa flights completely coincided in time with some of the Keflavik flights, so that the overlapping observation time was about 20 hours. A number of examples of interesting auroral X-ray events were detected in all of the flights. The continuous observation of cosmic-ray neutron intensity was carried out using the 12-NM-64 neutron monitor with multiplicity meters after adding two neutron counters to the previous 10-NM-64 neutron monitor. The cosmic-ray unusual increase was observed on February 25 and again on March 30, 1969. Another balloon observation was made by using a BF_3 neutron counter in order to observe an altitude dependence of the low energy atmospheric neutron intensity at high latitudes. This report gives a brief summary of the above-mentioned observations and some preliminary results.

1969年1月14日から2月14日までの1ヵ月間に,昭和基地でオーロラX線を観測するための気球観測が計10回行なわれた 飛揚はほぼ正常に行なわれ,1回あたり平均約20時間の観測に成功した その間オーロラX線強度の顕著な増加現象が多数検出された 気球飛揚成績の結果だけを速報する