Let F be a number field and p be a prime. In the successive approximation theorem, we prove that, for each integer n ≥ 1, finitely many candidates for the Galois group of the nth stage of the p-class tower over F are...Let F be a number field and p be a prime. In the successive approximation theorem, we prove that, for each integer n ≥ 1, finitely many candidates for the Galois group of the nth stage of the p-class tower over F are determined by abelian type invariants of p-class groups C1pE of unramified extensions E/F with degree [E : F] = pn-1. Illustrated by the most extensive numerical results available currently, the transfer kernels (TE, F) of the p-class extensions TE, F : C1pF → C1pE from F to unramified cyclic degree-p extensions E/F are shown to be capable of narrowing down the number of contestants significantly. By determining the isomorphism type of the maximal subgroups S G of all 3-groups G with coclass cc(G) = 1, and establishing a general theorem on the connection between the p-class towers of a number field F and of an unramified abelian p-extension E/F, we are able to provide a theoretical proof of the realization of certain 3-groups S with maximal class by 3-tower groups of dihedral fields E with degree 6, which could not be realized up to now.展开更多
Aiming at the problems of large load of rotation drive system,low efficiency of torque transmission and high cost for operation and maintenance of liner steering drilling system for the horizontal well,a new method of...Aiming at the problems of large load of rotation drive system,low efficiency of torque transmission and high cost for operation and maintenance of liner steering drilling system for the horizontal well,a new method of liner differential rotary drilling with double tubular strings in the horizontal well is proposed.The technical principle of this method is revealed,supporting tools such as the differential rotation transducer,composite rotary steering system and the hanger are designed,and technological process is optimized.A tool face control technique of steering drilling assembly is proposed and the calculation model of extension limit of liner differential rotary drilling with double tubular strings in horizontal well is established.These results show that the liner differential rotary drilling with double tubular strings is equipped with measurement while drilling(MWD)and positive displacement motor(PDM),and directional drilling of horizontal well is realized by adjusting rotary speed of drill pipe to control the tool face of PDM.Based on the engineering case of deep coalbed methane horizontal well in the eastern margin of Ordos Basin,the extension limit of horizontal drilling with double tubular strings is calculated.Compared with the conventional liner drilling method,the liner differential rotary drilling with double tubular strings increases the extension limit value of horizontal well significantly.The research findings provide useful reference for the integrated design and control of liner completion and drilling of horizontal wells.展开更多
Background Because patients with scar contracture of the neck are at a high risk of loss of the airway control after anesthesia induction, awake intubation is usually recommended. This retrospective clinical study was...Background Because patients with scar contracture of the neck are at a high risk of loss of the airway control after anesthesia induction, awake intubation is usually recommended. This retrospective clinical study was designed to evaluate the possibility, safety and efficacy of airway management and tracheal intubation under general anesthesia in such patients. Methods This retrospective study included 1683 patients from January 1994 to December 2006 with scar contracture of the neck, aged 1.5--67.0 years, who were scheduled for elective plastic surgery under general anesthesia in Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. Based on the results of the preoperative airway assessment, the patients were classified into group 1 （including 1375 patients with the atlanto-occipital extension of 〉20° and the Mallampatti＇s grade I or II） and group 2 （containing 308 patients with the atlanto-occipital extension of 〈20° and the Mallampatti＇s grade III or IV. In group 1, the intravenous induction and maintenance of anesthesia and succinylcholine for muscle relaxation were used. The intubation was done using a modified Macintosh technique. In group 2, the total intravenous anesthesia （TIVA） or the sevoflurane inhalation anesthesia was chosen and the spontaneous breathing was reserved during anesthesia. The intubation was performed by a fiberoptic stylet laryngoscope （FOSL）. The number of intubation attempts, intubation time and relative complications were observed and recorded in all patients. Results In group 1, the intubation was accomplished during the first attempt in 1279 cases （93%） and the intubation time was 〈3 minutes in 1304 cases （95%）. In group 2, the intubation was completed by the first attempt in 114 patients （37%） and 123 patients had an intubation time of 〈3 minutes （40%）. Tracheal intubation was successful by the second or third attempt in 96 patients in group 1 and 156 patients in group 2. Thirty-eight patients required four or more attempts which only occurred in group 2. The incidence of traumatic complication was 2.6% and 9.7% with one intubation attempt in groups 1 and 2, respectively, 12.5% and 17.0% with multiple intubation attempts （one vs multiple attempts in both groups, P 〈0.001）. All nontrauamatic complications occurred in group 2 and laryngospasm and hypoxemia were more common in patients using the TIVA compared to those using the sevoflurane inhalational anesthesia （P 〈0.001）. Conclusions This study demonstrated that with a precise airway evaluation, an adequate preoperative preparation and a pre-planned failed intubation strategy, the anesthetist who was experienced in the difficult airway management could safely perform airway control and tracheal intubation under general anesthesia in patients with scar contracture of the neck. We believe that this technique may be very valuable for the management of a known difficult airway because it is comfortable for the patient and saves time for the anesthetist.展开更多
文摘Let F be a number field and p be a prime. In the successive approximation theorem, we prove that, for each integer n ≥ 1, finitely many candidates for the Galois group of the nth stage of the p-class tower over F are determined by abelian type invariants of p-class groups C1pE of unramified extensions E/F with degree [E : F] = pn-1. Illustrated by the most extensive numerical results available currently, the transfer kernels (TE, F) of the p-class extensions TE, F : C1pF → C1pE from F to unramified cyclic degree-p extensions E/F are shown to be capable of narrowing down the number of contestants significantly. By determining the isomorphism type of the maximal subgroups S G of all 3-groups G with coclass cc(G) = 1, and establishing a general theorem on the connection between the p-class towers of a number field F and of an unramified abelian p-extension E/F, we are able to provide a theoretical proof of the realization of certain 3-groups S with maximal class by 3-tower groups of dihedral fields E with degree 6, which could not be realized up to now.
基金Supported by the Project of National Natural Science Foundation of China(52234002,42230814)。
文摘Aiming at the problems of large load of rotation drive system,low efficiency of torque transmission and high cost for operation and maintenance of liner steering drilling system for the horizontal well,a new method of liner differential rotary drilling with double tubular strings in the horizontal well is proposed.The technical principle of this method is revealed,supporting tools such as the differential rotation transducer,composite rotary steering system and the hanger are designed,and technological process is optimized.A tool face control technique of steering drilling assembly is proposed and the calculation model of extension limit of liner differential rotary drilling with double tubular strings in horizontal well is established.These results show that the liner differential rotary drilling with double tubular strings is equipped with measurement while drilling(MWD)and positive displacement motor(PDM),and directional drilling of horizontal well is realized by adjusting rotary speed of drill pipe to control the tool face of PDM.Based on the engineering case of deep coalbed methane horizontal well in the eastern margin of Ordos Basin,the extension limit of horizontal drilling with double tubular strings is calculated.Compared with the conventional liner drilling method,the liner differential rotary drilling with double tubular strings increases the extension limit value of horizontal well significantly.The research findings provide useful reference for the integrated design and control of liner completion and drilling of horizontal wells.
文摘Background Because patients with scar contracture of the neck are at a high risk of loss of the airway control after anesthesia induction, awake intubation is usually recommended. This retrospective clinical study was designed to evaluate the possibility, safety and efficacy of airway management and tracheal intubation under general anesthesia in such patients. Methods This retrospective study included 1683 patients from January 1994 to December 2006 with scar contracture of the neck, aged 1.5--67.0 years, who were scheduled for elective plastic surgery under general anesthesia in Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. Based on the results of the preoperative airway assessment, the patients were classified into group 1 （including 1375 patients with the atlanto-occipital extension of 〉20° and the Mallampatti＇s grade I or II） and group 2 （containing 308 patients with the atlanto-occipital extension of 〈20° and the Mallampatti＇s grade III or IV. In group 1, the intravenous induction and maintenance of anesthesia and succinylcholine for muscle relaxation were used. The intubation was done using a modified Macintosh technique. In group 2, the total intravenous anesthesia （TIVA） or the sevoflurane inhalation anesthesia was chosen and the spontaneous breathing was reserved during anesthesia. The intubation was performed by a fiberoptic stylet laryngoscope （FOSL）. The number of intubation attempts, intubation time and relative complications were observed and recorded in all patients. Results In group 1, the intubation was accomplished during the first attempt in 1279 cases （93%） and the intubation time was 〈3 minutes in 1304 cases （95%）. In group 2, the intubation was completed by the first attempt in 114 patients （37%） and 123 patients had an intubation time of 〈3 minutes （40%）. Tracheal intubation was successful by the second or third attempt in 96 patients in group 1 and 156 patients in group 2. Thirty-eight patients required four or more attempts which only occurred in group 2. The incidence of traumatic complication was 2.6% and 9.7% with one intubation attempt in groups 1 and 2, respectively, 12.5% and 17.0% with multiple intubation attempts （one vs multiple attempts in both groups, P 〈0.001）. All nontrauamatic complications occurred in group 2 and laryngospasm and hypoxemia were more common in patients using the TIVA compared to those using the sevoflurane inhalational anesthesia （P 〈0.001）. Conclusions This study demonstrated that with a precise airway evaluation, an adequate preoperative preparation and a pre-planned failed intubation strategy, the anesthetist who was experienced in the difficult airway management could safely perform airway control and tracheal intubation under general anesthesia in patients with scar contracture of the neck. We believe that this technique may be very valuable for the management of a known difficult airway because it is comfortable for the patient and saves time for the anesthetist.
