Search

Impedance spectroscopy (IS) provides a powerful, non-destructive way to acquire photovoltaic (PV) panels' internal impedance over a wide frequency range. Compared with specific workstation-based IS, converter-based IS performed as an added function of the PV power converter provides an attractive mean to achieve online measurements. It can help reduce overall system costs and facilitate online applications, as no additional equipment is required. However, the control strategy of the power converter should be specifically designed. This work aims to provide a systematic design guideline for control strategies of converter-based IS implementation. Meanwhile, a cooperative control scheme between maximum power point tracking (MPPT) and IS modes is proposed to ensure quasi-maximum output power even during IS monitoring mode. For IS mode, two control strategies, named unified control and separated control are designed and compared based on three commonly used compensation controllers in linear system control, i.e., proportional (P), proportional-integral (PI) and quasi-proportional resonant (QPR) controllers. In the unified control strategy, a single PI controller controls the DC and AC components together to meet the control objectives. Meanwhile, in the separated control strategy, a segmented lower pass filter (LPF) with a variable cut-off frequency is designed to effectively separate the DC component of the PV current from the AC perturbation signals. Finally, an experimental study is conducted to verify that under both control strategies, reliable and accurate IS measurements can be achieved. Particularly, the unified control strategy based on a single PI controller is chosen for the cooperative control between MPPT and IS modes considering its control simplicity, high tracking accuracy (i.e., 99.5% and 93.7% for DC and AC components separately) and sufficient signal-to-noise ratio (SNR) (i.e., 6.9 dB). The effectiveness of the online IS monitoring based on the internal impedance of the PV panel is verified as well.

We address the problem of rotational velocity and acceleration estimation from incremental encoders in the presence of sensor imperfections. In the area of motion control, measurements of shaft velocity and acceleration are often affected by large disturbances with a period of one revolution that arise from sensor imperfections and degrade the performance of most closed-loop control algorithms. We present an algorithm to identify and remove such periodic perturbations online, without the need of error compensation look-up tables, and without assuming constant velocity. The proposed algorithm is evaluated via open-loop experimental tests, and its implementation in closed-loop control applications is investigated via numerical simulations through a DC motor case-study.

AbstractIn a paper of 2002 Stefania Ferri gave a characterization of a quadric cone in PG(3, q). The statement of the theorem is true, but the first part of the proof does not work. The same author in a paper of 2004 gave a new correct, but quite tedious, proof of that part. In this short note we prove the first part in a simpler way.

In the area of traction and brake control, measurements of the rotational velocity of the wheels are often affected by large periodic disturbances that arise from sensor imperfections and degrade the performance of any closed-loop control algorithm. The aim of our paper is to address this problem. First, we present a detailed analysis of the most common sensor imperfections and their effect on their measured velocity. Then, we propose an estimation scheme that greatly reduces the periodic disturbances in order to provide a better estimate of the velocity, and we validate it via numerical simulations and experiments.

AbstractSince young people enjoy playing games, we propose a didactical situation in which magic squares become a very productive learning activity.

Nowadays, many projects have been conducted in order to reduce CO2emissions, with the objective of reducing energy consumption. In the context of the urban railway area, the energy consumption is huge. It is respectively split into 70% for the traction and 30% for station consumers. Many works have already been carried out on traction systems, but very few of them were oriented towards the station energy problematic. This paper describes the project led by “Efficacity” Institute which concerns the use of the braking energy to manage and optimize the railway station energy consumption.

Within the framework of the French inter lab SPACT project (Fuel Cell Systems for Transportation Applications), the behavior of a 5 kW PEM fuel cell stack, fed by humidified hydrogen and compressed air, is investigated in a test platform at Belfort, France.

Abstract: We apply Platform-Based Design (PBD) to the power optimization of a 14 bit, 80 MS/s pipelined Analog-to-Digital Converter (ADC) in a mixed signal formulation. A platform is a library of components and interconnects, each characterized with a set of behavioral, performance and composition models, that is used to raise the level of abstraction to enable system-level design. PBD is a meet-in-the-middle methodology that consists of two phases. The bottom-up phase generates a set of platform libraries that are exploited in the system hierarchy. The top-down phase allows exploring feasible solutions within the platform libraries and selecting the optimum implementation. To evaluate the cost of each implementation, the behavioral models available through platform abstraction are used both for digital and analog components. We provide an example of the use of the methodology and its features for analog circuits by modeling two amplifiers with different topologies as analog components, showing details of the analog characterization process. Then, we create a mixed signal platform library as a combination of an analog and a digital platform (bottom-up phase). The top-down phase performs optimization across the analog/digital boundary to minimize power consumption constrained to given noise and linearity requirements. Simulation results show that interesting power saving can be achieved, as much as 64% compared with an original hand-optimized ADC.

AimsTo report the outcomes of anorectal reconstruction by electrostimulated graciloplasty as part of abdominoperineal resection, on data prospectively collected over 10 years.Patients and methodsTwenty-three abdominoperineal resections were associated to coloperineal pull through, double graciloplasty and loop abdominal stoma. Fifteen patients also received an implantable pulse generator, either for unsatisfactory result after external-source intermittent electrostimulation and biofeedback (five cases) or during graciloplasty (10 cases). Follow-up was to a maximum of 10 years. Functional outcome was followed up in sixteen patients who underwent stoma takedown.ResultsMean actuarial survival at 5 years was 72.3%. Satisfactory results (score@?8) occurred in 75% of patients (three without and 13 with stimulator) in the early stages, decreasing to 57% at 1 year and gradually increasing up to 100% at 5 years and over.ConclusionsTotal anorectal reconstruction yields a good functional outcome over time. Thus, despite, and because of, a high complication rate and a great drain on resources, it should be considered a suitable procedure only for selected, strongly motivated patients.

Controversy still exists about the optimal lymph node (LN) dissection for potentially curable gastric cancer. For rational LN dissection it is important to know the incidence of metastasis at each LN station. For this purpose a computer program was developed using data from 4302 primary gastric cancers treated at the National Cancer Center Hospital in Tokyo between 1969 and 1989. To evaluate the accuracy of the computer program, the differences between the individual reports generated by the computer and the stored data were investigated in 282 Italian patients submitted to curative gastrectomy and D2or more extended LN dissections for gastric cancer. Receiver operating characteristic (ROC) analysis was used to assess the sensitivity and specificity of the program for predicting LN metastases in each of the 16 regional LN stations. The computer program showed good predictive ability for LN metastases in most of the 16 LN stations, as the areas under the curve ranged from 0.741 (station 15) to 0.944 (station 8), with a mean of 0.856. A critical cutoff point of 18% of the program's expected percentage was the value maximizing the validity of the prediction. Using an “absolute” cutoff point of 0%, the overall rate of false-negative (FN) predictions in 176 N+ patients was 11.9%; of these, 11 (6.2%) were absolute FNs, in which the program totally failed to estimate LN metastases; the remaining 10 cases (5.7%) were relative FNs because the specific prediction was positive for a different depth of stomach invasion. The low number of D3/D4lymphadenectomies in the historical database may affect the low estimate of metastases to N3/N4nodes generated by the program. Based on these data, the program predicts with good accuracy the extent of LN metastases from gastric cancer, but it is not recommended for directing the surgeon to perform more extensive lymphadenectomy.

Controversy still exists about the optimal lymph node (LN) dissection for potentially curable gastric cancer. For rational LN dissection it is important to know the incidence of metastasis at each LN station. For this purpose a computer program was developed using data from 4302 primary gastric cancers treated at the National Cancer Center Hospital in Tokyo between 1969 and 1989. To evaluate the accuracy of the computer program, the differences between the individual reports generated by the computer and the stored data were investigated in 282 Italian patients submitted to curative gastrectomy and D2or more extended LN dissections for gastric cancer. Receiver operating characteristic (ROC) analysis was used to assess the sensitivity and specificity of the program for predicting LN metastases in each of the 16 regional LN stations. The computer program showed good predictive ability for LN metastases in most of the 16 LN stations, as the areas under the curve ranged from 0.741 (station 15) to 0.944 (station 8), with a mean of 0.856. A critical cutoff point of 18% of the program's expected percentage was the value maximizing the validity of the prediction. Using an “absolute” cutoff point of 0%, the overall rate of false-negative (FN) predictions in 176 N+ patients was 11.9%; of these, 11 (6.2%) were absolute FNs, in which the program totally failed to estimate LN metastases; the remaining 10 cases (5.7%) were relative FNs because the specific prediction was positive for a different depth of stomach invasion. The low number of D3/D4lymphadenectomies in the historical database may affect the low estimate of metastases to N3/N4nodes generated by the program. Based on these data, the program predicts with good accuracy the extent of LN metastases from gastric cancer, but it is not recommended for directing the surgeon to perform more extensive lymphadenectomy.

The quantitative description of the proliferative activity of cancer cells correlates with the aggressiveness of malignant tumors. The aim of this retrospective study was to determine the biological effect of adjuvant therapy on metastatic lymph nodes from rectal cancer and to compare the results between patients treated with surgery alone and patients treated with preoperative radiotherapy. Expression of the proliferating cell nuclear antigen (PCNA) was examined in metastatic lymph node samples of 12 rectal cancer patients receiving and 14 patients not receiving preoperative radiotherapy. PCNA immunostaining was performed by an avidin-biotin complex immunoperoxidase technique. The results of the mean proliferation index (PI) between the two groups were compared. A semiquantitative PCNA grading system was also estimated. In patients receiving preoperative radiotherapy, the PI was 22.8 per cent, and only one patient had high proliferative grade. On the contrary, the PI in nonirradiated patients was 67.6 per cent, and nine patients showed high proliferative grade. Although not sufficient to reach significance in terms of prognosis, the present study confirms the clinical value of radiation therapy, and it supports the suggestion to treat Dukes’ C patients with preoperative radiotherapy to decrease the risk of local recurrence.

The postoperative course of 159 patients with early gastric cancer operated on between 1974 and 1987 was followed for a median of 7.3 years. The cumulative 10-year survival rate(s.e.) calculated using follow-up data to the end of 1989 was 90.6(2.7) per cent excluding operative death and that from causes other than gastric cancer, or 86.3(3.0) per cent when operative mortality was included. The overall 10-year survival rate(s.e.) was 77.3(3.7) per cent. Univariate analysis showed a significant difference in survival rates between cancers confined to the mucosa and those with submucosal invasion (P = 0.02), between patients with and without lymph node metastases (P = 0.05) and between those >50 and >50 years of age (P = 0.02). Using Cox multivariate analysis and a stepwise procedure for eight variables (sex, age, depth of invasion, lymph node metastases, presence of ulceration, location, histological type, type of surgery), age and histological type had the most significant effect on survival. Seven operative deaths were recorded. Eleven patients died from recurrent cancer and one is still alive with a gastric remnant recurrence. Other causes of death were metachronous primary cancer (six patients), cardiovascular disease (two), pneumonia (three), sepsis (one) and car accident (one). Although the prognosis of early gastric cancer is relatively good in western countries, patients should be carefully followed over a long period for late recurrence and for metachronous cancer, which has a high incidence.

Pulmonary function, pain and endocrine-metabolic response to surgical stress were compared in 50 patients with elective cholelithiasis who were randomly treated by laparoscopic cholecystectomy (LC) (group 1 = 29 patients) and by open cholecystectomy (OC) (group 2 = 21 patients). Data were stored in Dbse III and analysed using SPSS software. We compared the two groups using the unpaired t-test and by two-tailed chi-square test. No respiratory dysfunction was present after LC whilst in the OC group, pulmonary impairment lasted 5-7 days post-operatively. Pain evaluation by visual analogue scale confirmed that LC is less invasive and less harmful than OC. During surgery, hormonal response did not significantly differ in either group. In the post-operative period, an increase in prolactin and cortisol levels resulted in the OC group, which suggested stress. The findings of this study suggest that LC has more advantages than OC in the elective treatment of gallstones.

Summary: A collective review of 132 cases of insulin-secreting tumors of the pancreas treated by medical measures is reported. The most widely used drugs were diazoxide, corticoids and streptozotocin which have been effective in controlling hypoglycemia respectively in 48 out of 88 cases, in 15 out of 43 cases and in 10 out of 18 cases. Other drugs were of benefit only in a few cases, or were not sufficiently investigated. Results of treatment, evaluation of toxicity and incidence of side-effects suggest that the drug of choice in the treatment of insulinomas is diazoxide. Streptozotocin must be employed only in patients with malignant disease. The role and indications of medical management in patients with insulinomas are discussed.

Summary Preoperative knowledge of the gastric arterial blood-supply with special regard to anatomic anomalies is desirable for a correct surgical approach to this viscus and for the reduction of intra- and postoperative complication rates. The authors report their experience with the use of preoperative digital angiography in the evaluation of 46 consecutive patients undergoing gastric cancer surgery. Twenty of these (43.5 %) presented a vascular anatomy different from the normal pattern. In 6 (13 %), a double arterial anomaly was detected. Some anatomic anomalies of the celiac axis and superior mesenteric artery are described in relation to operative procedures during oncologic gastrectomies.

AIM: We present a case of squamous-cell carcinoma developing within perianal lichen planus. This is a chronic or recurrent cutaneous and/or mucosal dermatosis affecting less than 1 percent of the population. Neoplastic degeneration of cutaneous lichen planus is rare; only one case of squamous-cell carcinoma developing within perianal lichen planus has been described up until now in the international literature. CASE REPORT: Our case involved a 68-year-old woman with chronic, long-term lichen planus spreading all over the vulva and perianal region and the mucosa of the anal canal, where squamous-cell carcinoma developed within the perianal lichen planus. Treatment consisted of wide, circular excision of the perianal skin and mucosectomy of the anal canal up to as far as 1 cm above the dentate line. Reconstruction was performed by means of two V-Y bilateral subcutaneous flaps. CONCLUSION: Wide excision was performed not only to remove the squamous-cell carcinoma but also the lichen planus to prevent recurrence of metachronous or synchronous squamous-cell carcinoma. Follow-up at one year after surgery showed no local recurrence of either lichen planus or squamous-cell carcinoma, which suggests that surgical removal should be the therapy of choice for long-term, chronic perianal lichen planus that has proved to be resistant to medical therapy.

Abstract: We describe herein a clinical case in which a subcapsular splenic hematoma complicated chronic relapsing pancreatitis. A pathogenetic mechanism is postulated that explains the subacute insorgence of the liquid collection with the diffusion of proteolytic enzymes between the splenic capsule and parenchyma. Radical therapy, consisting of exeresis of the cystic formation, splenectomy and caudal pancreatectomy, is recommended for this extremely rare complication.

The postoperative course of 172 patients with early gastric cancer (EGC) was followed for a median 7 years to evaluate the causes of death, incidence and patterns of recurrence, and characteristic findings in the recurrent cases. The cumulative 10-year mortality rate (± SE) was 22 ± 3.7%. Seven patients (4.1%) died of operative mortality, 11 (6.4%) died of a recurrence of the gastric cancer, and 13 (7.6%) died of unrelated causes. Unrelated causes of death were metachronous primary cancer (n = 6), cardiovascular disease (n= 2), pneumonia (n= 3), sepsis (n= 1), and car accident (n= 1). Four patients died from gastric stump recurrence, three from liver metastases, two from lymph node metastases, and two from peritoneal dissemination. Using Cox multivariate analysis, histologic type had the most significant effect on recurrence. Although influenced by the tumor nature, the EGC prognosis is relatively good. Based on the results of this study, particularly in Western institutions, histologic examination of resection margins and lymphadenectomy should be improved. Moreover, patients must be carefully followed for late recurrence and metachronous cancer.

Abstract. The postoperative course of 172 patients with early gastric cancer (EGC) was followed for a median 7 years to evaluate the causes of death, incidence and patterns of recurrence, and characteristic findings in the recurrent cases. The cumulative 10-year mortality rate (± SE) was 22 ± 3.7%. Seven patients (4.1%) died of operative mortality, 11 (6.4%) died of a recurrence of the gastric cancer, and 13 (7.6%) died of unrelated causes. Unrelated causes of death were metachronous primary cancer (n = 6), cardiovascular disease (: n = 2), pneumonia ( n = 3), sepsis ( n = 1), and car accident ( n = 1). Four patients died from gastric stump recurrence, three from liver metastases, two from lymph node metastases, and two from peritoneal dissemination. Using Cox multivariate analysis, histologic type had the most significant effect on recurrence. Although influenced by the tumor nature, the EGC prognosis is relatively good. Based on the results of this study, particularly in Western institutions, histologic examination of resection margins and lymphadenectomy should be improved. Moreover, patients must be carefully followed for late recurrence and metachronous cancer.

The N-nitroso-compounds and the bacteriological contamination of gastric juice could represent a risk factor for cancer of the stomach when the mucosal barrier is altered. In the unresected stomach and gastric stump, the hypo-achlorhydria and bilopancreatic reflux permit the development of bacterial flora and the production of N-nitroso-compounds in the presence of nitrite. A survey was performed on 71 patients: 15 normal controls, 31 with gastroduodenal disease (9 gastrites, 10 gastric ulcers, 10 duodenal ulcers, 7 neoplasias), 20 patients with gastric resection (8 BI, 12 BII), using an endoscopic-histopathologic control and a chemical-bacteriological analysis of the gastric juice. We studied the gastric juice for the following parameters: pH, concentration of nitrite, identification of bacterial type, count and nitrate-reductase activity. An inverse relationship was found between the concentration of nitrite and the hydrogen ion concentration. In the alkaline gastric juice, we identified aerobic bacteria with nitrate-reductase activity and anaerobic bacteria. The latter has the ability to transform biliary salts into carcinogenic and cocarcinogenic compounds and to catalyze the nitrosations. The chemicobacteriological characteristics of the gastric juice from gastric ulcers (Johnson type I), atrophic gastrites, and resected stomachs lead one to think that there is a risk of carcinogenesis brought about by the N-nitroso-compounds.

Acute pancreatitis and leakage of pancreaticojejunal anastomosis are the most important causes of operative morbidity and mortality after pancreatoduodenectomy. We have introduced a modified technique for reconstruction that provides a functional exclusion of the pancreatic-jejunostomy in respect of the transit of gastric and biliary secretions. The immediate advantages of this technique are the reduction in the risk of leakage and the possibility of undertaking conservative treatment, in the case that leakage occurs. The preservation of the antral-pyloric unit, according to Traverso and Longmire,1 increases the functional features of the procedure, by reducing entero-gastric refluxes, and assuring a regulated gastric emptying. We herein present our series of 11 pancreatoduodenectomies (PD) for periampullary neoplasms and chronic pancreatitis. Throughout our series we experienced no cases of operative mortality. However, there was one specific instance of morbidity, consisting of one case of external biliary fistula by micro-dehiscence of the hepaticjejunostomy and which was later resolved by conservative treatment. Our most recent results have produced almost normal findings in terms of gastric secretion, gastric emptying and an absence of dumping syndrome, ulcers and refluxes.

There are major differences in cholecystectomy rates between different countries. We prospectively recorded all gallbladder operations in L'Aquila, Italy (a small town in central Italy with a population of about 98,700 inhabitants) from June 15, 1987 to June 14, 1988. During that year 210 cholecystectomies were performed (women and girls = 71.4), for a calculated yearly incidence rate of 0.212. Cholecystectomy was elective in 85.2, urgent in 8.6, and was performed in the course of other abdominal operations (mainly colon cancer) in the remaining 6.2. Half (44.3) of the patients were operated on because of at least one episode of biliary colic, and 9.0 because of an acute complication. Respectively 16.2 and 30.5 were operated on because of dyspeptic symptoms or to prevent symptoms or complications. Gallstones were not found in six, while exploration of the common bile duct revealed gallstones in seven patients. The chemical analysis showed that 84.7 were cholesterol stones (mixed or pure). We presume that most observed differences in cholecystectomy rates between different Western countries are more likely owing to differences in indications for surgery rather than to differences in prevalence of gallstones.

We report herein a case of an iatrogenic superior pancreaticoduodenal arterial aneurysm which ruptured into the duodenal stump of a Billroth II partial gastrectomy. Superselective angiography was used for the diagnosis, and successful embolization performed nonoperatively. A review of the literature revealed both the etiology and site of rupture in this case to be extremely uncommon.

Surgical treatment of obese patients is much debated in the literature because of the significant intraoperative risks related to comorbidities presented by this type of patients. Recent literature suggests that panniculectomy should follow bariatric surgery after the patient’s weight loss has been stabilized. However, when performed by laparotomy, bariatric surgery can be combined with panniculectomy. This paper presents the analysis of 325 cases of patients undergoing abdominal panniculectomy combined with bariatric surgery. The study highlights the risks, complications, and benefits of the combined procedure and describes a standardized technique for excision of a large abdominal panniculus in a short operating time.

The aryl sulfonates (I) are reduced with triethylammonium formate in the presence of a palladium diacetate/phosphine catalyst to form the corresponding arenes (II).

The dihydroxybenzenes(naphthalenes) (I) and (III) are oxidized with hydrogen peroxide in the presence of iodine and conc.