Effects of Projectile and Gun Parameters on the Dispersion

 Main battle tanks constitute one of the most powerful fire powers for the armoured land forces. To use this very high fire power efficiently, the dispersion of shot impacts becomes crucial. Dispersion is affected by the aerodynamic factors, gun-projectile interactions, projectile and gun dependent factors, manufacturing tolerances and environmental factors. The change in aerodynamic factors and environmental conditions varies the aerodynamic forces applied on the projectile and this affects the dispersion characteristics of the projectile. In this study, the effects of the changes in recoil stiffness, gun support stiffness, projectile muzzle velocity and manufacturing tolerances of projectile forward/rear bourrelet diameters on the dispersion for 120 mm L44 and L55 calibre guns are investigated. Armour piercing fin stabilised discarding sabot type projectile is used in the analysis. Statistical dispersion analyses including interior ballistic, in-bore balloting and exterior ballistic analyses are conducted using PRODAS ballistic software. According to the results, it is determined that the decrease in projectile/bore clearance (forward/rear bourrelet diameter) results in improved dispersion of ammunition. The 10% changes from the nominal recoil stiffness and the vertical support stiffness values have negligible effects on the dispersion. In addition, the results show that muzzle velocity variations influence the dispersion in vertical direction substantially. Using the procedure applied in this study, it is shown that different clearance conditions can be analysed and most suitable tolerances may be determined taking into consideration of both the gun system performance and manufacturability

Effects of Tank Gun Structural Components on the First Shot Hit Probability

Fire power for a main battle tank is one of the most important performance parameters like survivability and mobility. Fire power effectiveness is directly related to the first shot hit probability, performance of main gun, second armament, gun and turret drive system, fire control system, automatic target tracker, commander and gunner sight etc. First shot hit probability (a measure of cumulative effects of errors) is affected by the variations of the projectile parameters, the main gun structure uncertainties, fire control system errors, interaction between the projectile and the gun barrel and the unpredictable environmental changes. These errors and variations can be eliminated or minimised by understanding and simulating the firing event properly, manufacturing the related parts in high precision, using advanced fire control algorithms, and accurate sensors. In this review study, the effects of main gun structural components on the first shot hit probability are investigated taking into account all of the associated error sources. In order for a main battle tank to have both high and repetitive first shot hit probability under all battlefield conditions the gun structure should respond in a similar manner in successive firings without causing any abrupt change in performance. In this study, first the dynamic behaviour of gun/projectile system is discussed and then the design recommendations for the main gun components such as bearings, gun barrel, recoil system etc. to achieve higher first shot hit probability are reviewed

The effects of astaxanthin on salivary gland damage caused by cisplatin in the rat

Background: Cisplatin is a potent antineoplastic agent widely used for a variety of malignancies. However, it has many dose-limiting side effects such as neurotoxicity, cytotoxicity and ototoxicity. The aim of our study was to determine the effectiveness of astaxanthin (ASX) as a cytoprotective agent against cisplatin-induced cytotoxicity in the submandibular glands of rats.Methods: Thirty-six adult male Wistar albino rats were divided into six groups as follows: group I: saline control; group II: 75 mg/kg/day ASX; group III: 16 mg/kg cisplatin; group IV: 25 mg/kg/day ASX + cisplatin; group V: 75 mg/kg/day ASX + cisplatin; group VI: olive oil + cisplatin. In all groups, submandibular gland histopathological and histochemical investigations were done using a light microscope. Every rat section was semi-quantitatively scored. Neutrophil infiltration density, myoepithelial cell density in the degeneration area, degenerative granular duct cell density, degenerative seromucous acinus cell density, and changes in the content of the secretory granules of seromucous acini and granular ducts of the parenchyma and stroma were calculated.Results: The results of the analysis of the mean acinus area of the submandibular gland revealed that there was a significant decrease in cisplatin group rats when compared to control rats (p0.05, p=0.921). Similarities were observed in the mean ducts area with the group IV and the group V (p>0.05, p=0.571).Conclusions: These results suggest the possibility that the clinical use of ASX could reduce or prevent damage to the salivary gland of patients receiving cisplatin chemotherapy

Three-Dimensional Calculation of Sinus Augmentation Volume after Maxillary Sinus Floor Elevation

Abstract Objectives: This study aimed to calculate the volume of the maxillary sinus and grafted part of it with different modes of three-dimensional reconstruction software. Materials and Methods: This retrospective volumetric cone-beam computed tomography study was carried out on 21 patients/ 36 maxillary sinuses who had undergone maxillary sinus lift surgery using a lateral approach, between 2010 and 2016 at the Department Periodontology. All statistical analyses were performed by using the NCSS (Number Cruncher Statistical System, Kaysville, Utah, U.S.A.) software. P values 0.05). An occupied portion of the sinus cavity after lateral sinus floor elevation surgery was approximately 14.87 %. Furthermore, the volume through manual and automatical modes of the software do not affect the results (p>0.05). The right and left sides of the maxillary sinus volumes were not different from each other. Gender and measuring mode was not found to be related to volumetric values of the maxillary sinus cavity. Conclusions: The grafted volume of the sinus cavity was defined as a safe volume in terms of serious complications during and after the surgery

Impact of a well-organized collaborative team approach on mortality in patients with ST-segment elevation myocardial infarction

Objective: Fibrinolytic therapy remains a legitimate option for many patients presenting with acute ST-segment elevation myocardial infarction (STEMI). Shorter time- to- treatment for patients with STEMI administered fibrinolytic therapy has repeatedly been shown to reduce mortality. A well-organized collaborative team approach was implemented in April 2007. The purpose of this study was to examine the effect of implementing a well-organized collaborative team approach on the outcome in patients with acute STEMI treated with fibrinolysis. Methods: Sociodemographic, clinical, laboratory, and time interval data were prospectively collected on 109 consecutive patients (the study group) and 155 patients from the years 2005-2007 (the control group) retrospectively. A single-phone call was made to discuss case. Emergency department evaluation was bypassed for definitive case. An electrocardiogram was faxed to the on-call cardiologist for suspected case. Doorto-needle times were calculated as medians. Mortality was assessed by reviewing records of all patients visiting outpatient clinic. For the rest, information was obtained over the phone. Median door-to-needle times were compared using Mann-Whitney U test. The Fisher's exact test was used to compare 6-month mortalities. Results: Improvements were seen in door-to- needle times in the study group regardless of time of presentation (reduced from 59 minutes to 29 minutes during off hours) (reduced from 35 minutes to 18 minutes during regular hours) (p<0.0001). Mortality was significantly reduced in the study group (2 deaths, 1.8%) compared with the control group (12 deaths, 7.7%, p=0.048). Conclusion: The mortality of patients presenting with acute STEMI treated with fibrinolytic therapy was significantly reduced after optimal hospital organization. © 2010 by AVES Yayi{dotless}nci{dotless}li{dotless}k Ltd

Impairment of the left ventricular systolic and diastolic function in patients with non-alcoholic fatty liver disease

Background: Non-alcoholic fatty liver disease (NAFLD) is considered the liver component of the metabolic syndrome. We investigated the diastolic and systolic functional parameters of patients with NAFLD and the impact of metabolic syndrome on these parameters. Methods: Thirty-five non-diabetic, normotensive NAFLD patients, and 30 controls, were included in this study. Each patient underwent transthoracic conventional and tissue Doppler echocardiography (TDI) for the assessment of left ventricular (LV) diastolic and systolic function. Study patients were also evaluated with 24-hour ambulatory blood pressure monitoring. Results: NAFLD patients had higher blood pressures, increased body mass indices, and more insulin resistance than controls. TDI early diastolic velocity (E&#8217; on TDI) values were lower in NAFLD patients than the controls (11.1 &#177; 2.1 vs 15.3 &#177; 2.7; p < 0.001). TDI systolic velocity (S&#8217; on TDI) values were lower in NAFLD patients than the controls (9.34 &#177; 1.79 vs 10.6 &#177; 1.52; p = 0.004). E&#8217; on TDI and S&#8217; on TDI values were moderately correlated with night-systolic blood pressure, night-diastolic blood pressure, and night-mean blood pressure in NAFLD patients. Conclusions: Patients with NAFLD have impaired LV systolic and diastolic function even in the absence of morbid obesity, hypertension, or diabetes. (Cardiol J 2010; 17, 5: 457-463

Congenital absence of the pericardium: A rare cause of right ventricular dilatation and levoposition of the heart

Congenital absence of the pericardium is a rare cardiac defect with variable clinical presentations and is usually discovered incidentally. The pathology may lead to serious complications such as incarceration of cardiac tissue, myocardial ischemia, aortic dissection or valvular insufficiency. Diagnosis is not difficult so long as some tips are remembered. We present the cases of two patients with congenital absence of left pericardium

The ımpact of handicap severity on oral and periodontal status of patients with mental retardation

Aim: Mental retardation (MR) subjects comprise a considerable amount of the community and are susceptible to oral and periodontal problems due to insufficient oral care. The aim of this cross-sectional study was to determine the oral health and periodontal status of MR patients in Turkey with regard to periodontal indices and Decay missed filling teeth (DMFT) scores and compare findings according to severity of the MR. Materials and methods: One hundred and five MR patients were included to the study and divided into 3 groups according to MR severity diagnoses. Demographic variables like age, gender, disabled sibling, BMI, living an institution and clinical parameters like plaque index (PI), gingival index (GI), bleeding on probing (BOP), probing depth (PD), clinical attachment level (CAL), missing teeth and DMFT scores were recorded from all subjects. Appropriate statistical analyses were used to compare the findings. Results: There were no statistically significant differences between groups according to age, gender, disabled sibling, living status and DMFT scores. Clinical periodontal indices and the number of missing teeth were showed a statistically significant increasing trend with the severity of MR (p < 0.05). Correlation analysis showed significant positive correlations between PI and periodontal disease measures like GI, PD, CAL and BOP and also between PI and DMFT (p < 0.05). Conclusion: The deteriorated teeth condition and deprived periodontal health of MR patients may be most likely caused by the poor oral hygiene and may be worsen with the severity of the MR

The protective effect of astaxanthin on cisplatin-induced ototoxicity

Background. Promising studies have been conducted with many substances to reduce the ototoxic effects of cisplatin, but there is no treatment that completely eliminates the ototoxic effect. Objectives. To determine the effectiveness of astaxanthin (ASX) as a protective agent against cisplatin-induced ototoxicity. Materials and methods. Thirty-six rats were randomly divided into 6 groups. Group 1 received no drug injections except for anesthetics; group 2 received intraperitoneal (IP) olive oil only for 8 days; group 3 received only IP ASX 75 mg/kg dissolved in olive oil for 8 days; group 4 received a single dose of only IP 16 mg/kg cisplatin on the 5th day; group 5 received 25 mg/kg ASX IP daily for 8 days and a single 16 mg/kg dose of cisplatin on the 5th day; group 6 received 75 mg/kg ASX IP daily for 8 days and a single 16 mg/kg dose of cisplatin on the 5th day. The animals were tested for distortion product otoacoustic emissions (DPOAE) before and 3 days after cisplatin treatment. The animals in all groups were sacrificed under anesthesia on the 10th day. Before sacrifice, inferior vena cava blood samples were drawn into commercial tubes for biochemical analysis and their cochlea were prepared for histological analysis. Results. The ASX+cisplatin groups demonstrated significantly higher DPOAE thresholds when compared to the cisplatin-only group (p < 0.05). The ASX 25 mg/kg/day+cisplatin group showed a significant increase in total antioxidant capacity compared to the cisplatin-only group, whereas the ASX 75 mg/kg/day+cisplatin group had significantly lower total oxidative stress and oxidative stress index. Histologic results showed that the cortical organ was better preserved in the ASX+cisplatin groups compared to the cisplatin-only group, and the degeneration in the spiral ganglion and inner and outer hair cells was less visible in the ASX groups. Conclusions. Astaxanthin can protect hearing from cisplatin-induced ototoxicity, prevent cellular degeneration and significantly reduce oxidative stress