Chọc hút tổn thương dưới hướng dẫn nội soi phế quản siêu âm (EBUS-TBNA) dùng để chẩn đoán các tổn thương trung thất, rốn phổi. Chúng tôi nghiên cứu giá trị chẩn đoán và độ an toàn của thủ thuật như là một phương pháp chẩn đoán ban đầu. Phương pháp nghiên cứu: nghiên cứu hồi cứu mô tả cắt ngang từ tháng 9/2017 tới tháng 7/2021. Kết quả: EBUS -TBNA có độ chẩn đoán chính xác 69%; độ nhạy, đặc hiệu, giá trị dự báo dương tính, giá trị dự báo âm tính lần lượt là: 62%, 100%, 100%, và 38.9%. Không có biến chứng nào được ghi nhận. Kết luận: EBUS - TBNA là thủ thuật an toàn, hiệu quả, nên được sử dụng như một dụng cụ ban đầu để chẩn đoán các tổn thương trung thất, rốn phổi.

Fly ash is a waste byproduct of thermal power plants or steel plants with a low density. Study on using fly ash to produce lightweight construction materials will is a new application of this material resource. Pha Lai fly ash is a byproduct from Pha Lai Thermal Power Joint Stock Company, in which the main mineral component was mullite (15-20%), quartz (14-16%), carbon (5-7%). The content of the amorphous component was about 67-73%. The chemical composition of Pha Lai mainly was SiO2 (51.73%), Al2O3 (23.22%), Fe2O3 (4.23%). To fabricate the lightweight material from Pha Lai fly ash, the fly ash was mixed with additive materials to create binders following two ways: (1) lime + fly ash and (2) geopolymer technology. For the way of lime + fly ash, with the optimal mixture ratio was fly ash:lime: water = 10:2:1, the lightweight material samples had the bulk density of 1.32g/cm3, the compressive strength of 3.91 MPa, satisfied the Vietnamese standard TCVN 6477-2011 for concrete bricks. Applying the geopolymer technology, with the optimal mixture ratio was fly ash: NaOH/Na2SiO3: Al powder = 100:45:0.15, NaOH/Na2SiO3 ratio = 1:2, the lightweight materials obtained the bulk density of 0,62g/cm3, the compressive strength of 1,54 MPa, satisfied the Vietnamese standard TCVN:9029-2017 for Lightweight concrete - Foam concrete and non-autoclaved concrete products-specification.

In Vietnam, calcium carbide residue (CCR) from the acetylene gas factories are not properly treated, causing serious environmental pollution. Based on mineral composition determined by XRD, calcium carbide residue consisted mainly of portlandite (70-72%), calcite (14-16%), hydrocalumite (6-8%), and chemical composition determined by XRF method composed of CaO (53.02%), LOI (39.72%). This calcium carbide residue can be used as a source of hydrated lime, mixed with fly ash, sand, and cement to produce non-calcined bricks and test results show that brick specimens achieved compressive strength 3.0-7.5 MPa, water absorption 12.3-17.5%, density 1.28-1.80kg/cm3. The test bricks satisfied Vietnamese standards for construction bricks.

The study was carried out to assess the suitability of Tam Bo bentonite for application in peloid. By using the XRD analysis method, the results showed that the mineral component of Tam Bo bentonite was mainly smectite (montmorillonite) (55–73%), illite (10-14%), quartz (10–16%), and minor minerals such as siderite, feldspar, goethite, chlorite and kaolinite. Chemical composition of the samples analyzed by the XRF method composed of a high amount of SiO2 (51.38–55.16%) and Fe2O3 (5.31–7.97%), low content of Al2O3 (14.58–20.87%), and the other oxides with low content. The analysis result using the ICP-OES method indicated that bentonites in Tam Bo consisted of trace elements such as As, Ba, Cr, Cd, Co, Cu, La, La, Pb, Sb, Sc, V, Zn, and their content is similar to the values in peloid for the commercial use. Tam Bo bentonite has a pH value of 8.17, a very high CEC index (71 mg/100g), a plasticity index of 28%, expandability of 70%. All of the samples did not contain pathogenic bacteria. The study result confirms that Tam Bo bentonite responses to the criteria for making the peloid and similar to the peloids of Vale das Furnas (in Portugal), Calda (in Italy), Archena (in Spain).

The mineral component of kaolin clay in Tung Ba commune analyzed by X-ray diffraction is composed mainly of kaolinite (24-27%), illite (26-30%) and quartz (40-44%). Chemical composition (wt%) of Tung Ba kaolin determined by X-ray fluorescence (XRF) shows SiO2 at 59.92-64.98, Al2O3: 18.95-20.82, Fe2O3: 2.28-3.95, SO3: 2.47-4.66, CaO: 0.12-0.36, MgO: 1.72-2.13 and TiO2 at 0.75-1,08. To fabricate geopolymer ceramic, kaolin clay was transformed into metakaolin with the optimal parameters of calcination: the temperature at 750 degrees C and heating time of 120 min. Obtained metakaolin is mixed with mixtures of NaOH/Na2SiO3 (40%wt) with ratios of 0.2, 0.25, 0.33, 0.5 and NaOH molarities are 10M, 12M, 14M. Testing geopolymer ceramics after 28 days had a compressive strength of 40-196 KG/cm(2), water absorption of 15.25-17.98% and density of 1.54-1.69 g/cm(3), totally satisfied the Vietnamese standard for construction bricks and ceramics.

Based on the reconstruction of the thermal evolution of granitoid batholith, represented by the Song‐Chai gneiss‐granite massif (Northern Vietnam), the long‐term existence of granitoid magma at deep levels of the Earth's crust (H≥25 km, Δt~20–50 Ma) is established. The geodynamic analysis of the granitoid batholith and mathematical modeling of its thermal history shows that the magmatic chamber should be considered as a thermal trap at the lower level of the crust, which preserved residual granite melts for a long time. Activation of the magmatic chamber occurs in post‐collisional strike‐slip fault zones and is accompanied by tectonic exhumation of large crustal segments. As a result, the batholith is transformed into a Cordilleran‐type metamorphic core complex, residual rare‐metal melts are emplaced, and, commercial deposits are thus formed.

This paper presents the characteristics of the occurrence of ionospheric scintillations at low-latitude, over Vietnam, by using continuous data of three GSV4004 receivers located at PHUT/Hanoï (105.9°E, 21.0°N; magnetic latitude 14.4°N), HUES/Hue (107.6°E, 16.5°N; magnetic latitude 9.5°N) and HOCM/Ho Chi Minh city (106.6°E, 10.8°N; magnetic latitude 3.3°N) for the period 2006–2014. The results show that the scintillation activity is maximum during equinox months for all the years and depends on solar activity as expected. The correlations between the monthly percentage scintillation occurrence and the F10.7 flux are of 0.40, 0.52 and 0.67 for PHUT, HUES and HOCM respectively. The distribution of scintillation occurrences is dominant in the pre-midnight sector and around the northern crest of the equatorial ionization anomaly (EIA), from the 15°N to 20°N geographic latitude with a maximum at 16°N. The results obtained from the directional analysis show higher distributions of scintillations in the southern sky of PHUT and in the northern sky of HUES and HOCM, and in the elevation angles smaller than 40°. The correlation between ROTI and S4 is low and rather good at PHUT (under EIA) than HOCM (near equator). We found better correlation in the post-midnight hours and less correlation in the pre-midnight hours for all stations. When all satellites are considered during the period of 2009–2011, the range of variation of the ration between ROTI and S4 is from 1 to 7 for PHUT, from 0.3 to 6 for HUES and from 0.7 to 6 for HOCM.

The paper presents a method for computing the ionospheric total electron content (TEC) using the combination of the phase and code measurements at the frequencies f1 and f2 of the global positioning system, and applies it to study the TEC variations and disturbances during the magnetic storm in March 2015 using GPS continuous data in the Southeast Asia region. The computation results show that the TEC values calculated by using the combination of phase and code measurements are less dispersed than the ones by using only the pseudo ranges. The magnetic storm whose the main phase was on the 17th March 2015, with the minimum value of the SYM/H index of -223 nT is the biggest during the 24th solar cycle. In the main phase, the crests of the equatorial ionization anomaly (EIA) expanded poleward with large increases of TEC amplitudes, that provides evidence of the penetration of the magnetospheric eastward electric field into the ionosphere and of the enhancement of the plasma fountain effect associated with the upward plasma drifts. In the first day of the recovery phase, due to the effect of the ionospheric disturbance dynamo, the amplitude of northern crest decreased an amount of about 25% with respect to an undisturbed day, and this crest moved equatorward a distance of about 11o, meanwhile the southern crest disappeared completely. In the main phase the ionospheric disturbances (scintillations) developed weakly, meanwhile in the first day of the recovery phase, they were inhibited nearly completely. During the storm time, in some days with low magnetic activity (Ap<~50 nT), the ionospheric disturbances in the local night-time were quite strong. The strong disturbance regions with ROTI > 0.5 concentrated near the crests of the EIA. The latitudinal-temporal TEC disturbance maps in these nights have been established. The morphology of these maps shows that the TEC disturbances are due to the medium-scale travelling ionospheric disturbances (MSTID) generated by acoustic-gravity waves in the northern crest region of the EIA after sunset moving equatorward with the velocity of about 210 m/s.ReferencesAbadi P., S. Saito, and W. Srigutomo, 2014. Low-latitude scintillation occurrences around the equatorial anomaly crest over Indonesia, Ann. Geophys., 32, 7-17.Afraimovich E. L., 2008. First GPS-TEC evidence for the wave structure excited by the solar terminator, Earth, Planets and Space, 60, 895-900.Afraimovich E. L., E. I. Astafyeva, V. V. Demyanov, I. K. Edemskiy, N. S. Gavrillyuk, A. B. Ishin, E. A. Kosogorov, L. A. Leonovich, O. S. Lesyuta, K. S. Palamartchouk, N. P. Perevalova, A. S. Polyakova, G. Y. Smolkov, S. V. Voeykov, Y. V. 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Science of the Earth, formerly Vietnam Journal of Earth Sciences, is a peer-reviewed journal to publish high-quality articles on the entire range of earth sciences and the environment, focused on the Asia Pacific region and their correlations and connections to the globe. The journal publishes fundamental and applied research in earth sciences and the environment, including geology, geophysics, geography, soil science, hydrology, meteorology, oceanography, petroleum, geohazards, environmental sciences, environmental engineering, sustainable development, geoinformatics, geodesy, GIS, and remote sensing.

The statistic characteristics of ionospheric scintillation occurrence over Vietnam region have been studied using the continuous data from three GSV4004 receivers at Hanoi, Hue and Ho Chi Minh city during 2009-2012 period. The local time variation, seasonal variation and directional variation of scintillation occurrences in each stations were considered. The obtained results showed that the ionospheric scintillation over Vietnam region, mainly occurred at night time between 20 to 24 local time. The occurrence of ionospheric scintillation depend on the season and solar activity, with the maximum occurrence frequency on the equinox months (March, April and September, October) and significant enhancements on the strong active solar years (2011-2012). Over Vietnam region, ionospheric scintillation occurs concentratively on the equatorial ionisation anomaly crest, from the 13oN to 21oN geographic latitude with maximum at about 15oN. The ionospheric scintillation occurs mainly within the elevation angle smaller 40o and concentrate on some deterministic azimuth angles at each station.ReferencesAarons J.,1982: Global morphology of ionospheric scintillations, Proc. IEEE, 70, 360-378.Abadi P., Saito S., and Srigutomo W., 2014: Low-latitude scintillation occurrences around the equatorial anomaly crest over Indonesia, Annales Geophys., 32, 7-17.Basu, S., S. Basu, J. Aarons, J.P. McClure, and M.D. Cousins, 1978: On the coexistence of kilometer- and meter-scale irregularities in the nighttime equatorial F region, Journal of Geophysical Research, 83 (A9), pp. 4219 - 4226.Basu S., E. Kudeki, S. Basu, C. E. Valladares and E. J. Weber, 1996: Scintillation, plasma drifts, and neutral winds in the equatorial ionosphere after sunset, Journal of Geophysical Research, Vol. 101, N.A12, 26795-26809.Beniguel Y., and Adam JP, 2007: Ionosphere Scintillation and their Effect on the Positioning Errors, IEEA, proccesding, France.Cervera M. A. and R. M. Thomas, 2006: Latitudinal and temporal variation of equatorial ionospheric irregularities determined from GPS scintillation observations, Ann.Geophys.,N.24, 3329-3341.Dierendonck V., A.J, John Klobuchar, Quyen Hua, 1993: Ionospheric Scintillation monitoring using commercial single frequency C/A code receivers, Proceedings of ION GPS-93.Kintner P. M., Ledvina B. M., and Paula E. R, 2007: GPS and ionospheric scintillations, Space weather, Vol.5, S09003, doi:10.1029/2007W000260.Trần Thị Lan, Lê Huy Minh, R. Fleury, P. Lassudrie Duchesne, A. Bourdillon, 2009: Bước đầu nghiên cứu nồng độ điện tử tổng cộng và nhấp nháy điện ly sử dụng số liệu các trạm thu GPS liên tuc ở Việt Nam, Tạp chí Các khoa học về Trái Đất. T. 31, 3, 212-223.Trần Thị Lan, Lê Huy Minh, 2011: Biến thiên theo thời gian của nồng độ điện tử tổng cộng và nhấp nháy điện ly theo số liệu GPS liên tuc ở Việt Nam, Tạp chí Các khoa học về Trái Đất. T. 33, N4, 681-689.Le Huy Minh, Amory-Mazaudier C.,Fleury R., Bourdillon A., Lassudrie-Duchesne P., L. Tran Thi, T. Nguyen Chien and T. Nguyen Ha, P. Vila, 2014 : Time variations of the total electron content in the Southeast Asian equatorial ionization anomaly for the period 2006-2011, Advances in Space Research, 54, 355-368.Rama Rao, P. V. S., Gopi Krishna, S., Niranjan, and Prasad, D. S. V. V. D, 2006: Study of spatial and temporal characteristics of L-band scintillation over the Indian low latitude region and their possible effects on GPS navigation, Ann. Geophys., 24, 1567-1580.Saito S., Maruyama T., Ishii M., Kubota M., Ma G., Chen Y., Li J., Duyen C. H., Truong T. L., 2008: Observation of small to large scale ionospheric irregularities associated with plasma bubbles with a transequatorial HF propagation experiment and spaced GPS receivers, Journal of Geophysical research, V.113, A12313.Valladares C. E., Villalobos J., Sheehan R., and Hagan M.P., 2004: Latitudinal extension of low laititude scintillations measured with a network of GPS receivers, Ann. Geophys., 22, 3155-3175.GSV GPS Silicon Valley, 2005: GSV4004/GSV4004A - GPS Ionospheric Scintillation & TEC Monitor, USER’S MANUAL.

We investigate the geospace response to the 2015 St. Patrick's Day storm leveraging on instruments spread over Southeast Asia (SEA), covering a wide longitudinal sector of the low-latitude ionosphere. A regional characterization of the storm is provided, identifying the peculiarities of ionospheric irregularity formation. The novelties of this work are the characterization in a broad longitudinal range and the methodology relying on the integration of data acquired by Global Navigation Satellite System (GNSS) receivers, magnetometers, ionosondes, and Swarm satellites. This work is a legacy of the project EquatoRial Ionosphere Characterization in Asia (ERICA). ERICA aimed to capture the features of both crests of the equatorial ionospheric anomaly (EIA) and trough (EIT) by means of a dedicated measurement campaign. The campaign lasted from March to October 2015 and was able to observe the ionospheric variability causing effects on radio systems, GNSS in particular. The multiinstrumental and multiparametric observations of the region enabled an in-depth investigation of the response to the largest geomagnetic storm of the current solar cycle in a region scarcely reported in literature. Our work discusses the comparison between northern and southern crests of the EIA in the SEA region. The observations recorded positive and negative ionospheric storms, spread F conditions, scintillation enhancement and inhibition, and total electron content variability. The ancillary information on the local magnetic field highlights the variety of ionospheric perturbations during the different storm phases. The combined use of ionospheric bottomside, topside, and integrated information points out how the storm affects the F layer altitude and the consequent enhancement/suppression of scintillations.

Improvements in representation of foE for use in the International Reference Ionosphere (IRI) model are investigated. The IRI model currently depends on the 12-month running mean of sunspot number to estimate the foE. Using the F10.7 daily and F10.7_81 indices as the new model drivers, results are compared to ionosonde measurements at low, mid and high latitudes during solar minimum and solar maximum. Results show that the IRI model estimates the foE parameter better at low-mid latitudes than at high latitudes, specifically during solar maximum. Using the F10.7 indices to derive the IRI model improves estimates of foE, specifically at low-mid latitudes. The F10.7_81 index was found to perform better than the daily F10.7 index. Improvements during solar maximum and during solar minimum were on average 3.5% and 1%, respectively. Therefore, the F10.7_81 index is recommended as IRI model driver for foE estimates. (C) 2016 COSPAR. Published by Elsevier Ltd. All rights reserved.

Les signaux radioelectriques se propageant sur un trajet Terre-satellite sont parfois perturbes par la scintillation ionospherique. Ce phenomene se traduit par l’apparition de fluctuations rapides du signal recu qui sont susceptibles d’affecter les performances du systeme. C’est en particulier le cas du GPS pour lequel les scintillations sont un sujet de preoccupation pour certaines applications exigeantes en termes de precision, de disponibilite et de fiabilite. Dans le present article, on rapporte les resultats d’une campagne de mesures de la scintillation en regions equatoriales. Cette campagne, menee dans le cadre de cooperations internationales, a permis de valider des outils specifiques de surveillance et de prevision de la scintillation.

Estimatlon of the relatlon between the total tropospheric water vapour and the precision of the absolute positioning by GPS in Vietnam

(Total tropospheric water vapour and precision of the absolute positioning by GPS in Vietnam)

The Hanoi Institute of Geophysics (Vietnam) will participate to international Heliophysical Year. This paper presents Vietnam‘s participation into this International cooperative project : the Vietnamese network of magnetometers, meteorological stations, ionosondes and GPS receivers involved in campaigns of measurements, the research field selected for the training of young Vietnamese scientists, and the Institutes involve in this training. This paper also presents some particularities of geophysical parameters in Vietnam : the strong amplitude of the equatorial electrojet observed by satellite data and confirmed by magnetic observations at the ground level presented for the first time to the international community, the monsoon signature etc. Finally the differences between the Asian sector and the African sector lead to the development of comparative studies between Asia and Africa.