Effective optimization of irrigation networks with pressure-driven outflows at randomly selected installation nodes.

This paper presents an innovative methodology for the design of pressurized irrigation networks. Compared to other methodologies proposed in the scientific literature, it features three novel aspects: (i) construction of peak demand scenarios based on the random selection of installation nodes for hydrant heads available in each sector of irrigated properties; (ii) realistic hydraulic modelling of outflows from hydrant heads by means of the pressure driven approach; and (iii) adoption of linear constraints to enforce the telescopic property in the distribution of diameters from the source towards the external areas of the network in the optimized design. The applications of the methodology to the real network serving an irrigated area of 750 ha in Northern Italy proved that the aspects (i) and (ii) contribute to the accurate modelling of the current network while highlighting its hydraulic deficiencies. The adoption of the linear constraints described in (iii) in the context of the bi-objective genetic optimization of network diameters resulted in the speeding up of the algorithm convergence. The results show how decision makers can choose the ultimate configuration based on budget considerations from the trade-off solutions obtained between installation costs and hydraulic performance, considering network layouts with different level of topological redundancy.

Optoelectronic mixing with high-frequency graphene transistors.

Graphene is ideally suited for optoelectronics. It offers absorption at telecom wavelengths, high-frequency operation and CMOS-compatibility. We show how high speed optoelectronic mixing can be achieved with high frequency (~20 GHz bandwidth) graphene field effect transistors (GFETs). These devices mix an electrical signal injected into the GFET gate and a modulated optical signal onto a single layer graphene (SLG) channel. The photodetection mechanism and the resulting photocurrent sign depend on the SLG Fermi level (EF). At low EF (<130 meV), a positive photocurrent is generated, while at large EF (>130 meV), a negative photobolometric current appears. This allows our devices to operate up to at least 67 GHz. Our results pave the way for GFETs optoelectronic mixers for mm-wave applications, such as telecommunications and radio/light detection and ranging (RADAR/LIDARs.).

Photo thermal effect graphene detector featuring 105 Gbit s-1 NRZ and 120 Gbit s-1 PAM4 direct detection.

One of the main challenges of next generation optical communication is to increase the available bandwidth while reducing the size, cost and power consumption of photonic integrated circuits. Graphene has been recently proposed to be integrated with silicon photonics to meet these goals because of its high mobility, fast carrier dynamics and ultra-broadband optical properties. We focus on graphene photodetectors for high speed datacom and telecom applications based on the photo-thermo-electric effect, allowing for direct optical power to voltage conversion, zero dark current, and ultra-fast operation. We report on a chemical vapour deposition graphene photodetector based on the photo-thermoelectric effect, integrated on a silicon waveguide, providing frequency response >65 GHz and optimized to be interfaced to a 50 Ω voltage amplifier for direct voltage amplification. We demonstrate a system test leading to direct detection of 105 Gbit s-1 non-return to zero and 120 Gbit s-1 4-level pulse amplitude modulation optical signals.

Serum ghrelin levels in growth hormone-sufficient and growth hormone-deficient patients during growth hormone-releasing hormone plus arginine test.

BACKGROUND AND AIMS: Ghrelin is an orexigenic hormone produced in the stomach and in other organs, exerting a wide range of metabolic functions, including stimulation of GH secretion. Ghrelin secretion is decreased by iv or oral glucose load as well as during euglycemic-hyperinsulinemic clamp and hypoglycemia. We evaluated the circulating ghrelin levels in GH-deficient (GHD) and in GH-sufficient (GHS) patients during GHRH plus arginine test. MATERIALS AND METHODS: The study group comprised 35 patients, including 20 with pituitary tumors, 12 with empty sella, 2 with short stature, and 1 with post-traumatic isolated GH deficiency. According to the results of GHRH plus arginine test, 14 patients were defined as GHD and 21 as GHS. Patients with central hypothyroidism, hypocorticism, and hypogonadism had been on replacement therapy for at least 3 months at the moment of the study. Blood samples were collected every 20 min up to 60 min after GHRH and arginine administration. RESULTS: By definition, GH response to GHRH plus arginine was higher in GHS than GHD group (p<0.0001). Basal serum ghrelin levels were not different in the two groups and did not correlate with body mass index, GH, IGFI and insulin concentrations. After GHRH plus arginine, serum ghrelin decreased significantly in both groups, with percent decreases ranging 13.3-66.6% in GHD patients (p=0.001) and 7.2-42.2% in GHS patients (p=0.004), with no significant difference in the two groups (p=0.12). CONCLUSION: Our results show that ghrelin secretion is not modulated by acute GH increase observed in GHS subjects during GHRH plus arginine infusion. The similar decrease of serum ghrelin after GHRH plus arginine stimulation in both GHS and GHD subjects demonstrated that there is no negative feedback of GH on ghrelin secretion.

Limited value of repeat recombinant human thyrotropin (rhTSH)-stimulated thyroglobulin testing in differentiated thyroid carcinoma patients with previous negative rhTSH-stimulated thyroglobulin and undetectable basal serum thyroglobulin levels.

CONTEXT: One year after initial treatment, low-risk differentiated thyroid cancer (DTC) patients undergo recombinant human (rh)TSH-stimulated serum thyroglobulin (Tg) (rhTSH-Tg) and neck ultrasound (US). OBJECTIVE: The need for more rhTSH-Tg in these patients is controversial. We evaluated the utility of a second rhTSH-Tg in DTC patients 2-3 yr after their first evaluation. RESULTS: At the first rhTSH-Tg, basal and stimulated serum Tg was undetectable in 68 of 85 patients. Neck US was unremarkable in all but one, who had evidence of lymph node disease. Seventeen of 85 patients had undetectable serum Tg that became positive after rhTSH, with negative imaging in 10 and evidence of disease in seven. Patients with no evidence of disease were reevaluated 2-3 yr later (second rhTSH-Tg). In patients in which the first stimulated Tg was undetectable, all had undetectable basal serum Tg, which remained undetectable after rhTSH in 66 of 67 patients (98.5%) and became detectable in one (1.5%) (positive neck US). In the 10 patients with detectable stimulated Tg in the first test, basal serum Tg and US were negative at the second test, but rhTSH-Tg became detectable in six. Compared with the first rhTSH-Tg, the second stimulated Tg in these six patients decreased in one, increased in three, and stabilized in two patients. CONCLUSIONS: The second rhTSH-Tg was informative in patients who had first stimulated Tg detectable but not in those who had undetectable Tg at the first test, in which the only patient with recurrence was diagnosed by neck US. Thus, rhTSH-Tg should be repeated only in patients who have had a positive first rhTSH-Tg and negative imaging.

Effectiveness of radioiodine (131-I) as definitive therapy in patients with autoimmune and non-autoimmune hyperthyroidism.

We evaluated the outcome of radioiodine (RAI) therapy in 100 consecutive patients treated in the period 2000-2001 for hyperthyroidism due to Graves' disease (GD), toxic adenoma (TA) and toxic multinodular goiter (TMG). Thyroid function was measured before and after therapy every 3-6 months up to 3 yr. Three years after therapy, 75% of TA patients were euthyroid, 18.7% were hypothyroid and 6.3% hyperthyroid. Of the TMG patients, 62.2% were euthyroid, 18.9% were hypothyroid and 18.9% hyperthyroid. In GD patients euthyroidism was achieved in 12.9% of the patients, hypothyroidism in 74.2% and hyperthyroidism persisted in 12.9%. Definitive hypothyroidism was significantly higher in GD (p<0.0001) than in TA and TMG patients. Overall, positive effect of RAI (definitive hypothyroidism or euthyroidism) was very high: 93.7% in TA, 81.1% in TMG and 87.1% in GD patients. Thyroid volume reduction was observed in all patients, but was higher in GD patients (mean reduction of 76%) and in TA patients (mean nodule reduction of 69%). In TMG, mean reduction was of 32%. The median activity of RAI received by the 86 cured patients was 555 MBq (15 mCi) compared to 407 Mbq (11 mCi) received by the 14 patients who remained hyperthyroid. No influence was found between outcome and clinical parameters at the moment of 131-I therapy. In conclusion, our results indicate that RAI therapy is highly effective and safe for the control of hyperthyroidism.

Routine insertion of permanent peritoneal dialysis catheters in the nephrology ward. The sliding percutaneous technique.

AIM: A prerequisite to the technical success of peritoneal dialysis in its different modifications is a safe, reliable, correctly positioned, and functioning peritoneal catheter. The ideal method for insertion of permanent catheters (PC) remains debatable. The most commonly used technique is an open surgical approach, by minilaparatomy. Others have proposed a blind approach, using either a trocar method or a modified Seldinger technique or an insertion by means of peritoneoscopy. METHODS: We describe our 5-year experience (May 1997 - June 2002) with 68 percutaneous PC insertions in 63 consecutive patients. A modified technique of percutaneous PC insertion was used that here we call sliding percutaneous technique (SPT): 1) a midline incision is made 4 cm below the umbilicus; the peritoneum is punctured using a straight plastic catheter with a stylet. The catheter is pushed caudally towards the left iliac fossa; 2) a straight stiff 90 cm stylet is inserted through the temporary catheter, which is subsequently removed. The stylet has 2 tips, a blunt proximal one, which is pushed through the catheter into the iliac fossa, and the distal one; 3) having the stylet in situ, a double-cuffed curled-end PC is mounted at the distal tip of the stylet starting from the curl; then, the PC is gently slid down along the stylet as a train does along the rail-way. PC failure was defined as mechanical dysfunction, persistent dialysate leak and persistent peritonitis, or exit site/tunnel infection requiring PC removal. Furthermore, PC failure was defined as early, if occurring in the first 30 days after PC placement, or late, if occurring more than 30 days post-operation. Life-table estimates of PC survival were determined by Kaplan-Meier analysis. RESULTS: Early complications: in the 1st month on dialysis, obstruction to dialysate flow was the commonest cause leading to PC failure. The early actuarial survival (AS) was 90%. Late complications: peritonitis was the commonest cause of PC failure. The late AS, i.e. excluding the catheter failures occurring in the 1st month post-operation, was 82% at 3 years. Global AS, i.e. including both early and late PC failures, was excellent (74% at 3 years). CONCLUSIONS: Even though this study is retrospective and does not compare percutaneous with surgical PC placement techniques, it allows us to state that percutaneous PC insertion is a well-tolerated, rapidly performed, side-room procedure that gives excellent results, above all when using SPT.

[An exceptionally severe hyperuricemia in acute renal failure caused by spontaneous tumor lysis syndrome (TLS)]. / Iperuricemia eccezionalmente severa in insufficienza renale acuta da sindrome da lisi tumorale spontanea.

Acute tumor lysis syndrome (TLS) is a catastrophic complication of the treatment of certain neoplastic disorders. It most commonly occurs in association with hematologic malignancies and manifests a few hours to a few days after initiation of specific chemotherapy. Acute spontaneous TLS has been described in leukemia and lymphoma and in some patients with solid tumors prior to institution of therapy. The findings that may be seen in acute TLS include hyperphosphatemia, hypocalcemia, hyperuricemia, hyperkalemia, and acute oliguric or anuric renal failure due to uric acid precipitation within the tubules (acute uric acid nephropathy) and to calcium phosphate deposition in the renal parenchyma and vessels. We report here a case of acute spontaneous TLS (high grade B-cell lymphoma of the right colon) in which serum uric acid concentration attained exceptionally high levels (36.7 mg/dL). The patient underwent acute oliguric renal failure soon after right colectomy. He was treated by means of a large infusion of saline. The renal function recovered in such a rapid way that no dialysis treatment was required. In conclusion the present case report has two peculiarities: that of being one of the rare examples of spontaneous TLS, and that of showing an exceptionally severe hyperuricemia, probably the highest ever reported in the literature. The administration of a large volume of saline was able to ensure a complete recovery of renal function. Therefore, hydration with saline remains the keystone in the prevention and treatment of acute TLS.

Anterior ischemic optic neuropathy and dialysis: role of hypotension and anemia.

The pathogenesis of anterior ischemic optic neuropathy (AION) primarily involves interference with the posterior ciliary artery blood supply to the prelaminar optic nerve. Uremic patients often have coexisting pathology such as hypotension (decreased blood delivery), or hypertension, atherosclerosis (increased resistance to blood supply), and anemia (low blood oxygen carrying capacity), predisposing them to AION. We describe a 49-year-old patient on dialysis for many years. He had long-standing hypotension, worsened during each dialysis treatment. He awoke one morning at age 48 complaining of blurred vision in the left inferior field. Based on the clinical course, funduscopic and fluorangiographic examination and visual field defects, AION was diagnosed. Nine months after the loss of vision in the left eye, vision in the right eye became blurred and worsened over the next 24 hours. The diagnosis of AION in the right eye was made. At the last examination ten months later, the patient, still amaurotic, was given a very poor prognosis for further recovery of the visual defects. Surprisingly, very few cases of AION have been reported in chronic uremic patients on dialysis: to the best of our knowledge, only 12 including ours. Most of these cases share some features, including hypotension above all and anemia as common risk factors. Neither the type of dialysis treatment (hemo-, peritoneal dialysis) nor sex seem to have any influence on the occurrence of AION. Uremic children can be affected. What is striking in the three published pediatric cases is that they all had polycystic kidney disease. Treatment of AION in all 12 cases consisted of a combination of steroids, i.v. saline, blood transfusions and rhEpo. AION was more frequently bilateral and irreversible, ending in permanent amaurosis. In conclusion, this study aims to stress that most cases of AION occurring in chronic uremic patients on dialysis have some common features, including hypotension above all and anemia as common risk factors.

Effect of acetate-free biofiltration on the anaemia of haemodialysis patients: a prospective cross-over study.

BACKGROUND: The discussion about the pathogenesis of renal anaemia, whether it is primarily due to relative erythropoietin (Epo) deficiency or to uraemic inhibition of erythropoiesis, is still open. Although it has so far not been possible to identify or isolate a substance retained in uraemia with a suppressive action directed specifically against red-cell production, dialysis therapy can improve the effect of both residual endogenous Epo and exogenous rHuEpo. To what extent the mode and/or the dose of dialysis influence Epo efficacy is as yet poorly understood. METHODS: This study was performed as a single-centre trial. The protocol included a run-in period of 4 months followed by a prospective cross-over study including 6 months each of acetate-free biofiltration (AFB) with a high-flux biocompatible membrane and standard bicarbonate dialysis (BD) with a low-flux cellulosic membrane in a random sequence. AFB is a haemodiafiltration technique based on a continuous post-dilution infusion of a sterile isotonic bicarbonate solution. At the start of the run-in period (and for the entire length of the study), rHuEpo administration was withdrawn; patients whose haemoglobin (Hb) levels dropped at a level <8.0 g/dl at one single monthly check, had to be withdrawn from the study. A blood sample was collected every month for the blood gas analysis and for the determination of blood urea nitrogen, serum creatinine, sodium, potassium, calcium, phosphorus, Hb, erythrocyte, reticulocyte, leukocyte and thrombocyte cell counts, mean globular volume and haematocrit. An equilibrated single pool Kt/V(urea)>1.2 was mandatory in both treatment modalities. Serum iron, total iron-binding capacity, and ferritin were checked every 3 months. RESULTS: Twenty-three of 137 haemodialysis patients were considered eligible for the trial on the basis of the entry criteria. Of these, 15 volunteered and only 10 completed the study. No significant differences in the haematological indices, in the biochemical parameters assessing body iron stores, or in i.v. iron dosage was observed when comparing AFB with BD treatments. The equilibrated single pool Kt/V(urea) was always >1.2 and in no case was a significant difference observed when comparing AFB with BD treatments. Treatment time was significantly different between the two treatments (262+/-2 min in BD and 249+/-1 in AFB, P<0.0001). Neither pre- nor post-dialysis systolic and diastolic blood pressures, pre-dialysis serum bicarbonate and pH, pre-dialysis serum sodium, potassium, calcium, or phosphorus were significantly different when comparing the two treatment modalities. All 10 patients completed the 1-year follow-up without any major side-effects. CONCLUSIONS: Our study did not show any improvement of anaemia when treating a highly selected patient group, in the absence of any Epo therapy, with AFB compared with standard BD. Even though these conclusions cannot be extended in toto to the entire dialysis population, in which there is a large proportion of Epo-treated patients with Hb levels around 11 g/dl, we may nevertheless conclude that when patients are well selected, adequately dialysed, and not iron- and/or vitamin-depleted, the effect of a haemodiafiltration technique with a high-flux biocompatible membrane is less than might be expected from the results of uncontrolled studies.

Efficacy and safety of haemodialysis treatment with the Hemocontrol biofeedback system: a prospective medium-term study.

BACKGROUND: Hypovolaemia has been implicated as a major causal factor of morbidity during haemodialysis (HD). A model biofeedback control system for intra-HD blood volume (BV) changes modelling has been developed (Hemocontrol), Hospal Italy) to prevent destabilizing hypovolaemia. It is based on an adaptive controller incorporated in a HD machine (Integra), Hospal Italy). The Hemocontrol biofeedback system (HBS) monitors BV contraction during HD with an optical device. HBS modulates BV contraction rates by adjusting the ultrafiltration rate (UFR) and the refilling rate by adjusting dialysate conductivity (DC) in order to obtain the desired pre-determined BV trajectories. METHODS: Nineteen hypotension-prone uraemic patients (seven males, 12 females; mean age 64.5+/-3.0 SEM years; on maintenance HD for 80.5+/-13.2 months) volunteered for the present prospective study that compared the efficacy and safety of bicarbonate HD treatment equipped with HBS, as a whole, with the gold-standard bicarbonate treatment equipped with a constant UFR and DC (BD). The study included three phases: Medium-term studies started with one period of 6 months of BD and always had a follow-up period of HBS treatment ranging from 14 to 30 months (mean 24.0+/-1.6); short-term studies started in September 1999, when all patients went back to BD treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase A). Afterwards, they once again started HBS treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase B). Every patient underwent acute studies during a single HD run, once during phase A and once in phase B. Resistance (R) and reactance (Xc) measurements were obtained utilizing a single-frequency (50 kHz) tetrapolar bioimpedance analysis (BIA). Extracellular fluid volume (ECV) was calculated from R, Xc, and height and body weight measurements using the conventional BIA regression equations. RESULTS: The overall occurrence of symptomatic hypotension and muscle cramps was significantly less in HBS treatment in both medium- and short-term studies. Self-evaluation of intra- and inter-HD symptoms (worst score=0, best score=10) revealed a statistically significant difference, as far as post-HD asthenia was concerned (6.2+/-0.2 in HBS treatment vs 4.3+/-0.1 in BD treatment, P<0.0001). No difference was observed between the two treatments when comparing pre- and post-HD lying blood pressure, heart rate, body weights and body weight changes in medium- and short-term studies. The residual BV%/ Delta ECV% ratio, expression of the vascular refilling, was significantly higher during HBS treatment in acute studies. CONCLUSIONS: HBS treatment is effective in lowering hypovolaemia-associated morbidity compared with BD treatment; this could be related to a greater ECV stability. Furthermore, HBS is a safe treatment in the medium-term because these results are not achieved through potentially harmful changes in blood pressure, body weight, and serum sodium concentration.

Prognosis of occupational asthma.

BACKGROUND: Occupational asthma (OA), is an important clinical condition with substantial morbidity and associated costs. Since the original description of OA we have learned a great deal about the natural history. The prognosis of OA is determined by many factors. These factors and confounding variables in the presentation of OA will be presented. RESULTS: A review of the available literature indicates that OA may have complete resolution or may persist for years following its initial presentation. CONCLUSION: The importance of timely removal or adequate respiratory protection from potential sources of OA is highlighted.