Minimization of the blocking time of the unreliable Geo/G_D/1 queueing system

In this paper we study the blocking time of an unreliable single-server queueing system $Geo/G_D/1$. The service can be interrupted upon explicit or implicit breakdowns. For the successful finish of the service we use a special service discipline dividing the pure service time $X$ (assumed to be a random variable with known distribution) in subintervals with deterministically selected time-points $0=t_0<t_1<dots <t_k< t_{k+1}; t_k < X le t_{k+1},$ and making a copy at the end of each subinterval (if no breakdowns occur during it) we derive the probability generating function of the blocking time of the server by a customer. As an application, we consider an unreliable system Geo/D/1 and the results is that the expected blocking time is minimized when the time-points t_0,t_1,... are equidistant. We determine the optimal number of copies and the length of the corresponding interval between two consecutive copies

Intraoperative colonoscopy - Indications and advantages

The introduction of colonoscopy as a routine method in the diagnostic and treatment practice is a new stage in coloproctology. As we know, the number of paraneoplastic diseases and multicentral forms of cancer increases. Based on the existence of determinate number of preoperative colonoscopical unexamined patients, we began the application of intraoperative "peranal colonoscopy". With the method of intraoperative colonoscopy were examined 25 patients. From them 19 were men and 6 women at the age of 31 to 65 years. In 25 examined patients we discovered 9 with undiagnosed preoperatively polyps over the stenosing tumor process. Knowing the opportunities of the intraoperative colonoscopy and based on our experience we propose that this method could be applied in urgent operative interventions of colon and rectum with un known source of haemorrhage. Intraoperative colonoscopy is a valuable diagnostic method in the surgeon's hands and its appropriate application to selected patients helps us having the correct operative behaviour

Investigation on the Effect of Application of Monopolar Electrocoagulation for Endoscopic Haemostasis in Bleeding Peptic Ulcers

The authors investigate the effect of application of monopolar electrocoagulation for endoscopic haemostasis in bleeding peptic ulcers. In group of 30 randomly selected patients with acute bleeding from gastroduodenal ulcers, classified after Forrest by Wirtz we apply endoscopic electrocoagulation. The authors reveal that the method of monopolar high-frequent diathermal coagulation in present days is not appropriate for the purposes of endoscopic haemostasis in acute bleeding from gastroduodenal ulcers

Treatment recommendations for multimodality management of rectal cancer with a foc us on radiotherapy indications

Colorectal cancer (CRC) is one of the most commonly diagnosed cancer in Europe and US A and one of the leading causes of cancer death worldwide with 30% of all CRCs diagnosed in the rectum. Numerous published trials prove that the treatment of rectal cancer requires multidisciplinary approach. In this article the treatment recommendations for rectal cancer with an emphasis on radiotherapy (RT) application are defined

The role of radiotherapy in the contemporary multimodality management of rectal cancer

During the last 20 years the results of a significant number of trials concerning the multimodality management of rectal cancer have been published. This led to improvement of rectal cancer treatment. Radiotherapy (RT) is part of the standard multimodality treatment of rectal cancer and results in 50% local control improvement. The findings of the trials have answered some questions like the modalities sequencing, the combination of RT and chemotherapy, the RT fractionation regimens and the required total dose in addition to surgery either local or radical, the application of contact RT in early rectal cancer and intraoperative radiotherapy (IOR T) in locally advanced and recurrent rectal cancer. Neoadjuvant chemoradiation (CRT) followed by total mesorectal excision (TME) is the current standard treatment of patients with locally advanced rectal cancer with improved local control over postoperative CRT. In spite of the improved locoregional control, controversies exists and other opportunities for improvement are being investigated. In the present paper, the evidence behind the current standard of RT and the controversies in the treatment of patients with rectal cancer are reviewed

Morphological Changes in the Tissues Under The Action of Nd: YAG Laser in Peptic Ulcer Bleeding

The autors carry out a morphological study of 60 endoscopic biopsies of stomach mucosa followed-up consequencently in time. The study describes the morphological changes in the tissues under the action of Nd:YAG laser beam in cases of acute bleeding from peptic ulcers. Study proves that Nd:YAG LFC has lasting haemostatic and epithelising effect, i. e. it exerts a long-lasting therapeutic effect

The role of optical and virt ual colonoscopy in colorectal neoplasms

Purpose: High prevalence of colon carcinoma explains the continued high mortality rate of this disease.Utilizing a strategy of virtual colonoscopy (VC) in patients aged over 50 years with optical colonoscopy (OC) following-up for removal of detected adenomatous polyps may result in lowering the colon cancer death rate. However, VC diagnostic potential has not been widely recognized yet.Material and methods: This article reviews the currently available in diagnostic options in colorectal neoplasms and discusses their advantages and drawbacks.Results: VC has many advantages over the existing options and its several drawbacks can be mitigated so that it would become a valuable diagnostic modality. A strategy that utilizes VC for screening of patients over the age of 50 years and OC for screening high-risk individuals and those with positive VC findings would result in a significantly reduced colon cancer mortality rate.Conclusion: Both OC and VC (i.e., CTC and MRC) progress toward the clinical needs as new technologies are developed and applied to overcome the drawbacks of these diagnostic methods. Each of them plays a unique role for colon cancer prevention

Our experience in laparoscopic adrenalectomy

Purpose: Laparoscopic adrenalectomy (LA) has become the procedure of choice to treat functioning and non-functioning adrenal tumours. With improving experience, large adrenal tumours (> 5 cm) are being successfully tackled by laparoscopy.Material and methods: Thirty-five laparoscopic adrenalectomies performed in 32 patients for adrenal lesions during the period from 2006 to 2012 were analyzed.Results: Mean tumour size was 5,03 cm (range, 2-11 cm). Tumour size was larger than 8 cm in four patients. The lesions were localized on the right side in 17 patients and on the left one in 15 patients while bilateral tumours were established in three patients. Functioning tumours were present in 22 out of 32 patients. Average blood loss was 112 mL (range, 20-400 mL) with the mean operating time being 144 min (range, 45-270 min). Three patients underwent conversion to open procedure. Final histology revealed malignant tumours in three of 32 patients (9,52%).Conclusion: LA is safe and feasible for large adrenal lesions. Mere size should not be considered as a contraindication to laparoscopic approach in large adrenal masses. Graded approach, perfect preoperative assessment and planning, team work and adherence to anatomical and surgical principles are the key to success

The value of endo rectal ultrasound

In the last twenty years, endorectal ultrasound (ERUS) has become the primary method for locoregional staging of rectal cancer. ERUS is the most accurate modality for assessing local depth of invasion of rectal carcinoma into the rectal wall layers (T stage). Lower accuracy for T2 tumors is commonly reported, which could lead to sonographic overstaging of T3 tumors following preoperative therapy. Unfortunately, ERUS is not as good for predicting nodal metastases as it is for tumor depth, which could be related to the unclear definition of nodal metastases. The use of multiple criteria might improve accuracy. Failure to evaluate nodal statuscould lead to inadequate surgical resection. ERUS can accurately distinguish early cancers from advanced ones, with a high detection rate of residual carcinoma in the rectal wall. ERUS is also useful for detection of local recurrence at the anastomosis site, which might require fine-needle aspiration of the tissue. Overstaging is more frequent than understaging, mostly due to inflammatory changes. Limitations of ERUS are operator and experience dependency, limited tolerance of patients, and limited range of depth of the transducer. The ERUS technique requires a learning curve for orientation and identification of images and planes. With sufficient time and effort, quality and accuracy of the ERUS procedure could be improved