[en] Recent advances in ultrashort pulse laser technology allowed the generation of pulses shorter than 10-fs from Ti:sapphire lasers. The invention and progress of chirped mirror technology which can provide approximately constant negative group delay dispersion over a broader bandwidth than any other dispersive optical system, offer the potential for approaching the gain bandwidth limit in Ti:sapphire. The goal of this thesis was to develop chirped mirror-dispersion-controlled (MDC) sub-10 fs Ti:sapphire lasers and study the characteristics of sub-10 fs pulses. First, an all-chirped-mirror formed ring Ti:sapphire oscillator was constructed, which could produce nearly bandwidth-limited 7.5-fs optical pulses directly from an oscillator for the first time. Using this laser, the carrier phase shift of ultrashort light-wave packets was measured by means of interferometric cross-correlation. Our experiments lead us to the conclusion that controlling the carrier phase in light pulses may become feasible. The second part of this thesis focused on the development of high-peak-power MDC sub-10 fs Ti:sapphire oscillators. Pulses with a peak power of > 1 MW were demonstrated for the first time from a cw mode-locked laser. The peak intensities in excess of 5 x 10 ¹³ W/cm² were obtained at the focus of a specially designed lens. The first comprehensive noise characterization of a sub-10 fs Ti:sapphire laser has also been performed. Finally, with the latest chirped mirrors, a 1.5-MW peak-power, all-solid-state MDC Ti:sapphire laser which yielded 6 fs pulses was developed. (author)

No abstract available

[en] The latest technological developments in horizontal drilling and hydraulic fracturing are driving a commercial scale extraction of unconventional fossil fuels in various regions of the world. Europe's position in relation to the exploitation of unconventional fossil fuels is this has to be made under a paradigm of coherence between the technical and economic-financial aspects and environments and public trust, which are essential and which will eventually would enable the viability of exploiting these resources.This requires, by those decision makers, both industry and regulators, a comprehensive management of the risks associated with these exploitations, which implies the need to develop tools of analysis and assessment to environmental impact and risk. The exploitation of unconventional hydrocarbons in formations of shale requires the creation of a network of artificial fractures to connect with production well Horizontal wells are drilled for this purpose and go on for several km into the shale formation. During drilling, a mixture of oil, gas and formation water is pumped to the surface. The water is separated from oil and gas in tanks or pools. The flowback and produced water contains different kinds of chemicals in varying concentrations: salt, oil and other organic compounds, suspended solids, bacteria, naturally occurring radioactive elements (NORM), and any element injected with the fracturing fluid. The concentration of these elements in the water may be increased due to the treatments suffered by flowback and produced water for disposal. Due to the large variability of contaminants in the flowback and produced water and the potentially large volumes involved, the determination of the its composition is essential for proper management of them and to prevent health, safety and environmental risks. This report covers the risk analysis of an unconventional gas extraction project, the initial assessment of the risks associated with the use and management of water and introduces how it is possible to determinate at the initial stages of the project which inorganic contaminants may be present in the flowback and produced water.

[en] The latest technological advances in hydraulic fracturing and horizontal drilling are promoting a commercial scale extraction of unconventional fossil fuels in several regions of the world. Although there is still no commercial scale extraction in the Member States of the EU, potential stocks in some of them, as in the case of Spain, stimulate the need to carry out precautionary previous studies. These, based on the experience in the USA, will allow to define the characteristics that a priori should include a project of unconventional gas extraction, so that their safety is maximized by minimizing the likelihood of adverse effects on the environment. In unconventional gas production a fracturing fluid, typically water, with different types of additives is injected into the reservoir at very high pressure in order to create fractures to increase the porosity and permeability of the rock. In this scenario the flowback and produced water (water brought to the surface during the extraction of gas or oil) is usually a mixture of fluids injected and brines present in the repository. The quality of the flowback and produced water is variable. Its salinity varies from similar to drinking water to several times more saline than seawater. Furthermore, different compounds other than salt can be present in various amounts in the flowback and produced water: oil and other organic compounds, solids in suspension, bacteria, naturally occurring radioactive elements (NORM), and any of the elements injected with the hydraulic fracturing fluid. Due to the high variability of contaminants in the flowback and produced water as well as potentially large volumes involved, composition of flowback and produced water and the analysis of the risks associated with them is an important aspect to consider from the initial phases of project development of unconventional gas extraction. This report covers the risk analysis of an unconventional gas extraction project, the initial assessment of the risks associated with the use and management of water and introduces how it is possible to determinate at the initial stages of the project which organic contaminants may be present in the flowback and produced water.

[en] Soil and groundwater contamination has been and continues to be a significant concern for many industrial sites. The presence of contaminants in groundwater poses severe risk to human health and impacts water resource sustainability. A reliable simulation of contamination reactive transport is desired for most industrial pollution management. A smart system is constructed for soil and groundwater contaminant estimation and prediction in our group with artificial intelligence. The system consists of four main parts: database construction, model generation, forward simulation, and inverse modeling. With site related hydrogeologic and atmospheric data, both concept and numerical model are generated automatically in the system. The model is able to simulate the contaminant reaction and transport from point or non-point pollution in the subsurface system. By collecting real-time wireless data from the sensors on site, the model itself and parameters in the model are spontaneously adjusted to enhance the model accuracy and precision. Thus, this smart system can provide an early warning showing when and where there are large changes in hydraulic or contaminant situation. By improving our understanding of how the contaminants are interlinked and driven by the hydrogeology conditions, we could avoid or reduce environmental risks at contaminated sites.

[en] The wettability, fingering effect and strong heterogeneity of carbonate reservoirs lead to low oil recovery. However, carbon dioxide (CO2) displacement is an effective method to improve oil recovery for carbonate reservoirs. Saturated CO2 nanofluids combines the advantages of CO2 and nanofluids, which can change the reservoir wettability and improve the sweep area to achieve the purpose of enhanced oil recovery (EOR), so it is a promising technique in petroleum industry. In this study, comparative experiments of CO2 flooding and saturated CO2 nanofluids flooding were carried out in carbonate reservoir cores. The nuclear magnetic resonance (NMR) instrument was used to clarify oil distribution during core flooding processes. For the CO2 displacement experiment, the results show that viscous fingering and channeling are obvious during CO2 flooding, the oil is mainly produced from the big pores, and the residual oil is trapped in the small pores. For the saturated CO2 nanofluids displacement experiment, the results show that saturated CO2 nanofluids inhibit CO2 channeling and fingering, the oil is produced from the big pores and small pores, the residual oil is still trapped in the small pores, but the NMR signal intensity of the residual oil is significantly reduced. The final oil recovery of saturated CO2 nanofluids displacement is higher than that of CO2 displacement. This study provides a significant reference for EOR in carbonate reservoirs. Meanwhile, it promotes the application of nanofluids in energy exploitation and CO2 utilization.

[en] Purpose: In a continuing effort to improve conformal radiation therapy with Cobalt-60 units, a 60-leaf MLC was designed, manufactured, and released to market. This work describes the physics measurements taken to characterize the clinical performance of this MLC. Methods: A 60 leaf MLC was custom designed with tungsten leaves of 4.5 cm height, single focused, achieving field size of 30×30 cm^2 when mounted on a 100cm SAD Cobalt-60 unit. Leakage and output factor measurements were performed using a single ion chamber in a solid water phantom. Penumbra and surface dose were measured using scanning chambers and diodes in a water phantom. Radiation-light coincidence measurements were performed using radiographic films. Results: With MLC mounted, measured penumbras at all depths are smaller than with jaws only. Surface doses were not significantly affected by the presence of MLC, and remained below values recommended by regulatory bodies. Light-radiation coincidences were found to be better than 3 mm for all field sizes. Leakage through the MLC was found to be strongly dependent on field size, increasing from 1.0 % for a 10×10 cm field to 2.0% for a 30×30 cm field. Such results meet the requirements of IEC 60601-2-11. The MLC was found to have significant influence on the output factor, when field size defined by MLC is significantly smaller than field size defined by jaws. Such effect is also observed on linear accelerators, but it is more pronounced on Cobalt-60 units. A 10×10 “diamond” MLC shape inside a 14×14 cm jaw showed output factor that is 5.7% higher than 10×10 cm field defined by matching MLC and jaws. Conclusion: The MLC offers clinically acceptable performance in penumbra, surface dose, and light-radiation coincidence. Several units of this MLC have recently been installed and used clinically. Validation of Cobalt-60 based IMRT with this MLC is ongoing. The authors are employees of Best Theratrnics Ltd.

[en] Objectives: To investigate the clinical distribution and drug resistance of Klebsiella pneumoniae pulmonary infection in patients with hypertensive intracerebral hemorrhage after minimally invasive surgery. Methods: A total of 658 patients with hypertensive intracerebral hemorrhage who underwent minimally invasive surgery admitted to the intensive care unit (ICU) and the Department of Neurology of Affiliated Hospital of Hebei University from January 2015 to January 2020 were enrolled and divided into two groups: the observation group and the control group. Three hundred and thirty-three cases with postoperative pulmonary infection were included into the observation group, and 325 cases without postoperative pulmonary infection were divided into the control group. The intubation time, neurological deficiency score and Glasgow coma scale (GCS) of the two groups were analyzed and compared. Automatic microbial identification system was utilized to isolate bacteria from patients in the observation group, identify Klebsiella pneumoniae, and analyze Klebsiella pneumoniae infection, clinical department distribution, and age distribution. The KirbyBauer method was adopted to carry out the drug susceptibility test of Klebsiella pneumoniae infection. Results: The intubation time and neurological deficiency score of patients with hypertensive cerebral hemorrhage in the observation group were significantly higher than those in the control group (p<0.05), while the GCS score was significantly lower than that in the control group (p<0.05). A total of 403 strains of pathogenic bacteria were isolated from 325 patients in the observation group, of which 52 strains of Klebsiella pneumoniae were detected in 52 patients with postoperative pulmonary infection, accounting for 12.90%. The detection rates of Klebsiella pneumoniae in ICU and neurology department were 53.85% and 46.15%, respectively. Klebsiella pneumoniae had the highest detection rate (40.38%) in people aged 70 years and above. Moreover, fifty-two strains of Klebsiella pneumoniae showed low drug resistance rate (<20%) to cefoperazone/sulbactam, piperacillin/tazobactam, cefoxitin, imipenem, meropenem, amikacin, ciprofloxacin, and levofloxacin. Conclusion: For patients with hypertensive cerebral hemorrhage who have pulmonary infection after minimally invasive surgery, risk factors causing infection should be identified in time, their Klebsiella pneumoniae infection should be correctly monitored, and antibiotics should be taken rationally to effectively promote the elimination of brain edema in patients and protect the cranial nerve function of patients. (author)

[en] Cavernous sinus metastastasis of carcinoma is rare. We present a 57-year old Chinese man who was diagnosed as a case with hypopharyngeal carcinoma (T/sub 3/ N/sub 2b/ M/sub 0/ ). He received the radical surgery and radiotherapy. After six months, it was found that the metastases of hypopharyngeal carcinoma appeared in the right cavernous sinus. The patient was treated with Gamma knife radiosurgery. However, 10 months later, the clinical sign and mass reappeared, then Gamma knife radiosurgery was used again at the double dose. After 17 months, the tumor 29 months. Gamma knife radiosurgery may be effective in the treatment of patients with cavernous sinus metastasis. (author)

[en] The vacuum-powders insulation is the commonest cryogenic insulation. Adding metal powders improves the performance of the insulation, but it is concerned that metal powders sink resulting from vibration, shock and thermal cycling in the using process decreasing the performance of the insulation. In this paper it was obtained that the above effect was eliminated if the diameter of metal powder reached a critical value by theoretical analyses, calculations and experimental result. A method was proposed that extended this insulation application and improved the performance of insulation