Two-dimensional superconducting phase in LaTiO3/SrTiO3 heterostructures induced by high-mobility carrier doping.

In this Letter, we show that a superconducting two-dimensional electron gas is formed at the LaTiO3/SrTiO3 interface whose transition temperature can be modulated by a back-gate voltage. The gas consists of two types of carriers: a majority of low-mobility carriers always present, and a few high-mobility ones that can be injected by electrostatic doping. The calculation of the electron spatial distribution in the confinement potential shows that the high-mobility electrons responsible for superconductivity set at the edge of the gas whose extension can be tuned by the field effect.

[Pre- and postoperative contribution of Doppler ultrasonography in superficial venous surgery of the popliteal fossa]. / Apport de l'écho-Doppler pré et postopératoire dans la chirurgie veineuse superficielle de la fosse poplitée.

AIMS OF THE STUDY: Does preoperative Duplex Scan (DS) allow to determine anatomy of the ending of the short saphenous vein (SSV), gastrocnemius vein (GV) and reflux in popliteal vein (PV), SSV and GV. Postoperative DS was performed to detect deep vein thrombosis (DVT) and GV thrombosis. MATERIAL AND METHODS: From June 94 to November 95 one hundred and eighty lower limbs operated for SSV were included consecutively and prospectively. Mean age in these 154 patients was 52 yr (24-80) with a sex ratio 4F/1M. An anatomical classification was previously defined. Type A: separate termination of SSV and GV; Type B: common ostium of SSV and GV in the popliteal vein; Type C: common trunk of the SSV and GV; Type D: Others. Forty-eight limbs (26.10%) had ligation of GV: 21 (11.10%) for reflux and 27 (16%) for anatomical or surgical reasons. Ten type A with GV reflux (10/31 = 32%) were not treated. Eighty two patients (45%) received preventive low molecular weight heparin (LMWH) treatment including the 48 limbs whose GV were ligated. RESULTS: Anatomical correlation between DS and surgery findings were calculated. Positive predictive values of DS in the different types were: A, 77%; B, 68%; C, 90%; D, 79%. That gave a global predictive value of 80%. Two limited DVT were identified in group D by postoperative DS (2/10 = 1.1%). These two patients had complete recanalization of PV without reflux. In the group of limbs which had ligation of GV we identified 37.5% of GV thrombosis. In the group without ligation of GV we found 3% of GV thrombosis. CONCLUSION: Duplex scanning appears to be the investigation of choice before surgery for superficial vein incompetence in the popliteal fossa. It is a reliable investigation to determine termination patterns of SSV and GV (80%). It brings to the surgeon essential information which helps in the management of surgical procedure and particularly to ligation of gastrocnemius veins. But at this time there is no consensus on this point. The occurrence of DVT after SSV surgery including GV ligation was very low. Two questions remain: is anticoagulation necessary in all patients or selective after surgery of the SSV? is Duplex Scan mandatory during postoperative monitoring? On the basis of this study, one recommendation can be made: A routine postoperative DS is necessary after ligation of the GV or when the dissection of the popliteal fossa has been extensive (Type D).

[Understanding the poor results after surgery for superficial venous insufficiency]. / Comprendre les mauvais résultats après chirurgie de l'insuffisance veineuse superficielle.

Effectiveness and value of surgical treatment in varicose veins remains difficult to assess for many reasons. They are discussed in details in front of this general review devoted to poor results after varicose vein surgery. An other pathology is often associated with venous insufficiency and is frequently missed and responsible of poor results. Many factors contribute to make uneasy assessment of poor results. The lack of objective criteria to appreciate the natural evolution of varicose disease different from one patient to another. The difficulty to grade clinical disease severity. Results published before the use of modern preoperative investigations make their report obsolete. Precise data of surgical treatment undertaken are often not detailed. The quality of therapists (surgeon or phlebologist) is uneasy to check. The difficulty to assess results after treatment: subjective results (patient) vs objective results (audit). Duration of follow-up. Imprecise vocabulary to qualify results. Clinical assessment remains the cornerstone but supplementary investigations must be undertaken. Duplex-Scan is currently accepted as the gold standard investigation. Phlebography or (and) plethysmography can be helpful in some cases. After detailed assessment patients can be classified in different groups. This classification allows to determinate the most adequate treatment. In some selected patients redosurgery is strongly recommended. Prevention of recurrence after surgical treatment of varicose veins can not be complete. Strict respect of several rules can however reduce it. They can be summarised as follows: Respect of temporary of definitive contraindications to surgical treatment. Thorough investigation before surgery. Preoperative precise aim of what must be treated by the surgical procedure. Correct operative procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effectiveness of combined repeat surgery and sclerotherapy after failure of surgical treatment of varicose veins]. / Valeur de l'association chirurgie itérative-sclérothérapie après échec du traitement chirurgical des varices.

UNLABELLED: From January 1985 to December 1986 one hundred and five patients (145 lower limbs) have been treated by redosurgery followed by sclerotherapy. It is a selected group because redosurgery decision was taken both by surgeon and angiologists on the basis that a significant reflux between the profunda system and the superficial system was present. The aim of this retrospective study was to assess results obtained by this therapeutic association with a follow-up from 5 to 6 years. Failure mechanisms of initial treatment, symptoms, preoperative investigations, redosurgery procedures are analysed. Results were estimated both by a questionnaire and an independent audit. Patient estimation: symptoms improvement 65%; cosmetics improvement 68%. Audit estimation: SYMPTOMS: excellent or good results: 78%, fair results: 12%, poor results: 10%. Cosmetics: excellent or good results: 30%, fair results: 53%, poor results: 17%. 82% of patients plebiscited redosurgery in cooperation with sclerotherapy.