Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO.

Research on advanced materials such as multiferroic perovskites underscores promising applications, yet studies on these materials rarely address the impact of defects on the nominally expected materials property. Here, we revisit the comparatively simple oxide MgO as the model material system for spin-polarized solid-state tunnelling studies. We present a defect-mediated tunnelling potential landscape of localized states owing to explicitly identified defect species, against which we examine the bias and temperature dependence of magnetotransport. By mixing symmetry-resolved transport channels, a localized state may alter the effective barrier height for symmetry-resolved charge carriers, such that tunnelling magnetoresistance decreases most with increasing temperature when that state is addressed electrically. Thermal excitation promotes an occupancy switchover from the ground to the excited state of a defect, which impacts these magnetotransport characteristics. We thus resolve contradictions between experiment and theory in this otherwise canonical spintronics system, and propose a new perspective on defects in dielectrics.

[A priori benign Leydig cell testicular tumor: enucleation or radical orchidectomy?]. / Tumeurs testiculaires à cellule de Leydig a priori bénignes: énucléation ou orchidectomie radicale?

The histological sections of 5 patients treated for clinically benign Leydig cell testicular tumour (LCTT) were reviewed according to histological criteria presumptive of malignancy. The absence of any sign of severity was only verified in a single case, as none of the other tumours could be considered to be strictly benign. In the light of these findings, great caution is required in conservative indications, especially as these tumours, when they are malignant, are particularly serious due to the inevitable diagnostic delay and their absence of radio- or chemo-sensitivity.

Extraperitoneal pelvioscopy in lymph node staging of bladder and prostatic cancer.

In view of the inadequate accuracy of radiological investigations, surgical lymphadenectomy is generally the last resort to assess lymph node involvement in bladder and prostatic cancers. Extraperitoneal pelvioscopy is a simple and effective method to avoid such invasive surgery, which is always slightly regrettable to perform purely for staging purposes. The investigation is performed with the patient under low spinal anesthesia via a short iliac incision using an instrument derived from the mediastinoscope. It allows biopsies from the external iliac, internal iliac, common iliac and obturator lymph node chains. We analyzed our results of pelvioscopy in 101 patients (36 prostatic and 65 bladder cancers). Extraperitoneal pelvioscopy, unilateral in 78 and bilateral in 23 cases, corrected the conclusions of the radiological assessment in 39% of the prostatic cancer cases and in 28% of the bladder cancer cases. The specificity and positive predictive value is 100%, sensitivity 84%, negative predictive value 93% and over-all reliability 95%. On the basis of the quality of the results and the low morbidity (5 cases of rapidly resolving lymphorrhea, 1 injury to the external iliac vein and 1 obturator nerve lesion), extraperitoneal pelvioscopy can be considered as a useful complement to the preoperative staging of bladder and prostatic cancer.

[The parathyroid risk in thyroid surgery. Argument against the early postoperative prescription of vitamin D. Experience with 729 thyroidectomies in 1988]. / Le risque parathyroïdien en chirurgie thyroïdienne. Plaidoyer contre la prescription post-opératoire précoce de vitamine D. Expérience de 729 thyroïdectomies en 1988.

729 consecutive patients underwent thyroidectomy in 1988 in the same institution, including 477 (68%) bilateral resections and 242 (33%) total thyroidectomies. An effort was made to see and save all 4 parathyroids and their blood supply. Early post-operative hypoparathyroidism was defined at day 5, by serum calcium less than 8 mg/dl. and serum phosphate less than 4 mg/dl or by serum calcium only if greater than 7.5 mg/dl. Patients afflicted with early hypoparathyroidism were given calcium tablets without any vit D for 1 year at most. Follow-up, checking serum Ca, P and i PIH was done on a 3 months basis during 1 year. Permanent hypoparathyroidism was defined by persistence of the above-mentioned criteria after 1 year, and eventually vit D was started. 27 patients (5.6% our of 477 bilateral thyroid resections) experienced early post-op hypoparathyroidism. Inciting factors were previous thyroid surgery (4), radioiodine treatment (2), modified neck dissection (2), sternal split with mediastinal node clearance (1), visualization of 1 parathyroid gland only (3 redo cases) and autotransplantation of more than 1 parathyroid (1 case). 1 patient was lost for follow-up. 25 others recovered a normal parathyroid function. 1 is permanently hypoparathyroid (1 redo case with other risk factors). Painstaking parathyroid dissection allows a 0% rate of permanent hypoparathyroidism after primary surgery, if vit D is not given in the early post-operative period. We suggest that avoidance of early vit D prescription in cases of early post-operative hypoparathyroidism, leading to mild sustained hypocalcemia, stimulates the spared parathyroid glands (including a possible 5th) and therefore allows full recovery of the parathyroid function.