Unilateral Clearance Research Articles

Analysis and Optimization Design of Gunpowder Gas Sealing Performance of a Revolving Chamber Automatic Mechanism

When the revolving chamber automatic mechanism fires, it is required to reserve a gap between the revolving chamber bushing and its bushing hole to move back and forth to realize the gunpowder gas sealing performance between the barrel bushing and the revolving chamber bushing. Its gas leakage failure modes mainly include the radial gap gas leakage between the revolving chamber bushing and its bushing hole as well as the transverse gap gas leakage between the end surfaces of the two bushings. Aiming at the two typical gas leakage failure modes, the analysis models of the revolving chamber bushing radial clearance and the transverse clearance of the end surfaces of the two bushings are established respectively. Combining with the load such as chamber pressure, the gas sealing performance is analyzed, the effects of unilateral clearance, groove and pushing force acting outer diameter on the gas sealing performance are analyzed, and the optimal design scheme of the gas sealing performance is put forward. Taking the maximum instantaneous flow as the evaluation index, the gas sealing performance of the revolving chamber automatic mechanism is improved by more than 30%. The research has important reference value for the design of gas sealing structure of revolving chamber gun.

Posture and Dynamics Analysis of Hydraulic Support with Joint Clearance under Impact Load

A hydraulic support is one of the key pieces of equipment in a fully mechanized coal-mining face. The shaft is seriously worn due to repeated support shifting in coal-mining operations, and the hydraulic support bears a large amount of impact load in the support process, leading to a threat to its dynamic stability. In order to study the impact load on the posture and dynamics of a hydraulic support, and considering the joint clearance of the hydraulic-support hinge point, based on the dynamics software Adams, the equivalent variable-stiffness damping system is used to replace the column, and the impact analysis model of the hydraulic support with joint clearance is established. The roof pressure is vertically applied to the load balance area of the top beam by static load, and the impact load is vertically applied to the top beam downward. Based on the above model, considering the different distributions of joint clearance, research about the influence of joint clearance on the posture and dynamic characteristics of the hydraulic support is carried out. The results show that when there is joint clearance on both sides of the hydraulic support, when the top beam bears the impact load, the X-axis PMR (position movement ratio) at different positions of the top beam is more than 80%, and the forward-tilt posture is obvious. When the hydraulic support has only unilateral clearance, the front end of the top beam bears the impact load, and the front end of the top beam moves laterally, while the rear end of the top beam mainly moves longitudinally. When the end of the top beam bears the impact load, the vertical PMR of the top beam is less than 1%. When the impact load acts on the side with joint clearance, the top beam has a certain degree of lateral offset, and the offset directions on both sides of the top beam are inconsistent. At this time, the top beam presents a torsional-bearing posture. When the front end of the top beam is loaded, the mechanical curve of each hinge point is higher than the rear-end load. For the hinge point on the side without clearance, the maximum load-fluctuation coefficient reaches 1.04, while for the hinge point on the side with clearance, the minimum load is 0 kN, which will mean some hinge points cannot to play a supporting role. The analysis results will be helpful to research hydraulic supports considering joint clearance.

Update on the clinical management of multiple endocrine neoplasia type 1.

This review provides an overview of novel insights in the clinical management of patients with Multiple Endocrine Neoplasia Type 1, focusing on the last decade since the last update of the MEN1 guidelines. With regard to Diagnosis: Mutation‐negative patients with 2/3 main manifestations have a different clinical course compared to mutation‐positive patients. As for primary hyperparathyroidism: subtotal parathyroidectomy is the initial procedure of choice. Current debate centres around the timing of initial parathyroidectomy as well as the controversial topic of unilateral clearance in young patients. For duodenopancreatic neuroendocrine tumours (NETs), the main challenge is accurate and individualized risk stratification to enable personalized surveillance and treatment. Thymus NETs remain one of the most aggressive MEN1‐related tumours. Lung NETs are more frequent than previously thought, generally indolent, but rare aggressive cases do occur. Pituitary adenomas are most often prolactinomas and nonfunctioning microadenomas with an excellent prognosis and good response to therapy. Breast cancer is recognized as part of the MEN1 syndrome in women and periodical screening is advised. Clinically relevant manifestations are already seen at the paediatric age and initiating screening in the second decade is advisable. MEN1 has a significant impact on quality of life and US data show a significant financial burden. In conclusion, patient outcomes have improved, but much is still to be achieved. For care tailored to the needs of the individual patient and improving outcomes on an individual basis, studies are now needed to define predictors of tumour behaviour and effects of more individualized interventions.

Could the Less-Than Subtotal Parathyroidectomy Be an Option for Treating Young Patients With Multiple Endocrine Neoplasia Type 1-Related Hyperparathyroidism?

Background: The surgical treatment of primary hyperparathyroidism (HPT) in patients with multiple endocrine neoplasia type 1 (MEN1) has evolved due the concern of permanent hypoparathyroidism. As the diagnosis has increased, the extent of operation has decreased. Most MEN1 patients requiring parathyroidectomy are younger than 50 years and they pose a difficult balance to achieve between persistent HPT and life-long hypoparathyroidism. The aim of the present study is to review our experience with a large series of patients with MEN1-related HPT (HPT/MEN1) treated at a single institution in order to find clues to a better treatment decision in these younger cases.Method: Retrospective analysis of consecutive HPT/MEN1 cases treated at a single institution with different operations: total parathyroidectomy and immediate forearm autograft (TPTX-AG), subtotal (STPTX), unintentional less than subtotal (U-LSTPTX) and intentional less than subtotal parathyroidectomy (I-LSTPTX).Results: Considering 84 initial cases operated on since 2011 (TPTX-AG, 39; STPTX, 22, U-LSTPTX, 13, and I-LSTPTX, 10), the rates of hypoparathyroidism were 30.8% (U-LSTPTX), 28.2% (TPTX-AG), 13.6% (STPTX), and 0% (I-LSTPTX). Two-thirds of them (68%; 57/84) were young (<50 years) or asdolescents. MIBI scan was more sensitive to show parathyroid glands and bilateral disease. Considering the concordance of MIBI and ultrasound for the possibility of unilateral clearance, it would be suitable to 22.6% of the cases. Intra-operative parathormone showed a significant decay even after unilateral exploration, but longer follow up is necessary. Overall, there were seven (4%) adolescents in 161 cases treated from 1987 to 2018, three underwent TPTX-AG and four had U-LSTPTX. Five are euparathyroid, one had mild recurrence, and one required a reoperation after 8 years due to the residual gland.Conclusions: Young patients are the most frequent candidates to parathyroidectomy. Less extensive procedures may be planned only if carefully reviewed preoperative imaging studies suggest a localized disease. Patients and their relatives should be fully informed of the risks and benefits during consent process. Future research with larger cohorts and long-term results are necessary to clarify if less than I-LSPTX or unilateral clearance are really adequate in selected groups of patients with HPT/MEN1 presenting lower volume of disease detected by preoperative imaging studies.

Unilateral Clearance for Primary Hyperparathyroidism in Selected Patients with Multiple Endocrine Neoplasia Type 1

BackgroundPrimary hyperparathyroidism is the most common manifestation of multiple endocrine neoplasia type 1 (MEN1). Guidelines advocate subtotal parathyroidectomy (STP) or total parathyroidectomy with autotransplantation due to high prevalence of multiglandular disease; however, both are associated with a significant risk of permanent hypoparathyroidism. More accurate imaging and use of intraoperative PTH levels may allow a less extensive initial parathyroidectomy (unilateral clearance, removing both parathyroids with cervical thymectomy) in selected MEN1 patients with primary hyperparathyroidism.MethodsWe performed a retrospective cohort study at a high-volume tertiary medical center including patients with MEN1 and primary hyperparathyroidism, who underwent STP or unilateral clearance as their initial surgery from 1995 to 2015. Unilateral clearance was offered to patients who had concordant sestamibi and ultrasound showing a single enlarged parathyroid gland. For both the groups, we compared rates of persistent/recurrent disease and permanent hypoparathyroidism.ResultsEight patients had unilateral clearance and 16 had STP. Subtotal parathyroidectomy patients were younger (37 vs 52 years). One patient in each group had persistent disease. One (13 %) unilateral clearance and five (31 %) STP patients had recurrent hyperparathyroidism after a mean follow-up of 47 and 68 months (p = 0.62). No unilateral clearance patients and two of 16 SPT patients had permanent hypoparathyroidism (p = 0.54).ConclusionsSome MEN1 patients with primary hyperparathyroidism who have concordant localizing studies may be selected for unilateral clearance as an alternative to STP. For appropriately selected MEN1 patients, unilateral clearance can achieve similar results as STP and has no risk of permanent hypoparathyroidism, and may facilitate possible future reoperations.

Renal sequential scintigraphy: unilateral clearance rate determination based on external measurements only.

A method of estimating the 131I-hippuran clearance of each kidney during renal sequential scintigraphy is presented. The clearance rates were obtained from the elaboration of the renal histograms and of a blood curve recorded on the precordium, directly compared with the injected dose. A function simulating the progressive deformation of the radioactive bolus as kidney perfusion is impaired was introduced into the computation. The method was tested on 23 patients who underwent simultaneous determination of the clearance rate with the Sapirstein method, the results being corrected to 1.73 m2 of body surface area. The correlation coefficient r between the obtained data (the sum of the clearance rates of the two sides) and the results of the Sapirstein method was 0.89.

Effect of vesicoureteral reflux on renal function in children with recurrent urinary tract infections

The functional damage caused by vesicoureteral reflux (VUR) has been examined by unilateral clearance studies in 22 children with recurrent urinary tract infection (UTI) and representing 23 kidneys with large VUR. 7 kidneys with small to moderate VUR and 14 kidneys without VUR. Inulin clearance, Na+ excretion and glucose reabsorption were determined. In kidneys without or with small and moderate VUR, UTI had no effect on renal function if treated. In kidneys with large VUR extending into the pelvis and dilating the ureter, there was a gradual deterioration of glomerular filtration rate (GFR) that was accelerated after the age of 6 yr. Before puberty more than 50% of renal function was lost despite strict medical care of the UTI. If this functional loss was unilateral, hyperfunction of the contralateral kidney was generally observed. Maximal glucose reabsorption was depressed in proportion to GFR. In kidneys with unilaterally low GFR, the fractional Na+ excretion was consistently increased as compared to the contralateral kidney with normal GFR. This adaptive increase in Na+ excretion must therefore be of intrarenal origin.

An experimental analysis of the effects of oestrogen on the thyroid gland of castrated adult male rats.

SUMMARY The uptake of 131I by the thyroid gland of the castrated adult male rat is increased 24 hr. and is maximal 48 hr. after the injection of a single dose of 50 μg. oestradiol. The response is not dose-dependent between 25 and 1600 μg. The thyroid:serum (T:S) concentration ratio for 131I is also increased by oestradiol with a time-course similar to the changes in uptake, but release of 131I-labelled hormone from the gland in vivo and radioactive phosphate uptake were not affected. Analysis of the kinetics of 131I accumulation by the blocked gland show that the effects on 131I uptake and T:S ratio were due to an increase in the clearance rate with a possible associated decrease in the exit rate constant for iodide from the gland to the blood. Under the conditions of these experiments, the effects of oestradiol are not consistent with their being produced by an increase in pituitary thyrotrophic hormone secretion; a direct action on the gland appears likely. These conclusions apply solely to the experimental conditions described here and do not provide the basis for any generalization about the action of oestrogens on the thyroid gland. The method of analysis developed for the estimation of the unilateral clearance constant and the exit rate constant, together with their standard deviations, is presented in an appendix.

EFFECTS OF CYANIDE, QO, AND DINITROPHENOL ON RENAL SODIUM REABSORPTION AND OXYGEN CONSUMPTION.

Effects on sodium reabsorption and oxygen consumption of the renal arterial injection of three metabolic inhibitors were studied by unilateral clearance techniques in anesthetized dogs. In control studies, 21.5 ± 2.3 mEq sodium were reabsorbed per millimole oxygen consumed within a range of sodium reabsorption of from 2 to 9 mEq/min. A total dose of 10–4 m cyanide depressed both sodium reabsorption and oxygen consumption in the injected kidney. Administration of 10–4 m Q0, the quinone nucleus of coenzyme Q, reduced sodium reabsorption and had a variable effect on O2 consumption. Dinitrophenol, in a total dose of 10–3 m, increased oxygen consumption without affecting the per cent of filtered sodium that was reabsorbed. The resultant Na:O2 ratios were 12:1. We conclude that the major fraction of O2 consumption energizes sodium reabsorption in the kidney perhaps via the classic route of ATP synthesis and hydrolysis. However, all three compounds used in this study would be predicted to decrease renal ATP concentrations. Yet only cyanide and Q0 decreased sodium reabsorption. Energy for sodium movement may come directly from oxidative metabolism bypassing synthesis and breakdown of ATP.