Extreme fluctuations in stochastic network coordination with time delays

We study the effects of uniform time delays on the extreme fluctuations in stochastic synchronization and coordination problems with linear couplings in complex networks. We obtain the average size of the fluctuations at the nodes from the behavior of the underlying modes of the network. We then obtain the scaling behavior of the extreme fluctuations with system size, as well as the distribution of the extremes on complex networks, and compare them to those on regular one-dimensional lattices. For large complex networks, when the delay is not too close to the critical one, fluctuations at the nodes effectively decouple, and the limit distributions converge to the Fisher-Tippett-Gumbel density. In contrast, fluctuations in low-dimensional spatial graphs are strongly correlated, and the limit distribution of the extremes is the Airy density. Finally, we also explore the effects of nonlinear couplings on the stability and on the extremes of the synchronization landscapes.

Building damage-resilient dominating sets in complex networks against random and targeted attacks

We study the vulnerability of dominating sets against random and targeted node removals in complex networks. While small, cost-efficient dominating sets play a significant role in controllability and observability of these networks, a fixed and intact network structure is always implicitly assumed. We find that cost-efficiency of dominating sets optimized for small size alone comes at a price of being vulnerable to damage; domination in the remaining network can be severely disrupted, even if a small fraction of dominator nodes are lost. We develop two new methods for finding flexible dominating sets, allowing either adjustable overall resilience, or dominating set size, while maximizing the dominated fraction of the remaining network after the attack. We analyze the efficiency of each method on synthetic scale-free networks, as well as real complex networks.

Dominating scale-free networks using generalized probabilistic methods

We study ensemble-based graph-theoretical methods aiming to approximate the size of the minimum dominating set (MDS) in scale-free networks. We analyze both analytical upper bounds of dominating sets and numerical realizations for applications. We propose two novel probabilistic dominating set selection strategies that are applicable to heterogeneous networks. One of them obtains the smallest probabilistic dominating set and also outperforms the deterministic degree-ranked method. We show that a degree-dependent probabilistic selection method becomes optimal in its deterministic limit. In addition, we also find the precise limit where selecting high-degree nodes exclusively becomes inefficient for network domination. We validate our results on several real-world networks, and provide highly accurate analytical estimates for our methods.

Minimum Dominating Sets in Scale-Free Network Ensembles

We study the scaling behavior of the size of minimum dominating set (MDS) in scale-free networks, with respect to network size N and power-law exponent γ, while keeping the average degree fixed. We study ensembles generated by three different network construction methods, and we use a greedy algorithm to approximate the MDS. With a structural cutoff imposed on the maximal degree we find linear scaling of the MDS size with respect to N in all three network classes. Without any cutoff (k_max = N – 1) two of the network classes display a transition at γ ≈ 1.9, with linear scaling above, and vanishingly weak dependence below, but in the third network class we find linear scaling irrespective of γ. We find that the partial MDS, which dominates a given z < 1 fraction of nodes, displays essentially the same scaling behavior as the MDS.

Coarsening of precipitation patterns in a moving reaction-diffusion front

Precipitation patterns emerging in a two-dimensional moving front are investigated on the example of NaOH diffusing into a gel containing AlCl3 . The time evolution of the precipitate Al(OH)_{3} can be observed since the precipitate redissolves in the excess outer electrolyte NaOH and thus it exists only in a narrow optically accessible region of the reaction front. The patterns display self-similar coarsening with a characteristic length xi increasing with time as xi(t) approximately sqrt[t] . A theory based on the Cahn-Hilliard phase-separation dynamics, including redissolution, is shown to yield agreement with the experiments.

Ovarian steroid cell tumor and a contralateral ovarian thecoma in a postmenopausal woman with severe hyperandrogenism

A 49-year-old woman presented with rapidly progressing hirsutism, receding hairline, male-pattern baldness and deepening of voice, which had developed over the past 2 years. Hormonal evaluation showed a markedly elevated serum testosterone level (418 ng/dl) and no evidence of increased production of cortisol, dehydroepiandrosterone, dehydroepiadrosterone-sulfate, androstenedione, or 17-hydroxyprogesterone. Transvaginal ultrasound examination suggested the presence of a small mass within the left ovary, but all other radiological studies, including adrenal and ovarian computed tomography, magnetic resonance imaging, radio-labelled cholesterol scintigraphy and positron emission tomography, were negative. Subsequently, bilateral selective venous sampling showed a marked testosterone gradient in the right ovarian vein. Bilateral salpingo-oophorectomy was performed (the patient had had a previous vaginal hysterectomy), and histopathological examination revealed a 10-mm steroid cell tumor within the right ovary and a 15-mm thecal cell tumor within the left ovary. The postoperative serum testosterone level returned to normal and the patient showed a slow regression of clinical symptoms. The simultaneous occurrence of a virilizing ovarian steroid cell tumor and an apparently non-functioning thecoma within the contralateral ovary emphasizes the potential pitfalls that may exist in the preoperative evaluation of patients with markedly increased testosterone production.

Eye health care in Hungary

PURPOSE

To describe eye health-care services provided by in patient Departments of Ophthalmology in Hungary as of 1998.

METHODS

A standardised questionnaire was sent to all Hungarian in-patient ophthalmic departments. The response rate was 100%, and data from six university departments and 56 hospitals with ophthalmic units are summarised.

RESULTS

During the 12-month period, a total of 78,008 ophthalmic operations were performed, by 489 ophthalmologists. They worked in 62 in-patient ophthalmic units having a total of 1952 beds. The cataract rate was 3564 operations per million inhabitants; intraocular lens implantation was performed on 97% of the cases. There were 591 corneal transplants, 1698 operations for retinal detachment and 510 vitrectomies for diabetic eye complications.

CONCLUSIONS

The level of ophthalmic care in Hungary, judged on the basis of key objective parameters including number of ophthalmic specialists, number of ophthalmic beds, and the rates of surgery, generally conforms to standards prevailing in Western Europe, in spite of financial difficulties and the consequent lack of investment in new equipment and instruments, both major and minor.

[Coronary angioplasty over 70 years of age]

In the two institutions between January 1992 and December 1998 PTCA-s were done in 196 pts (123 male and 73 female) aged 70 years or more, with the 57 (20.1%) 6 months redo procedures performed out to June 1999, totally 247 interventions. The dilatations were done in 230 vessels (218 natives and 12 grafts) and in 254 stenoses, as of 1996 in 73 cases with stent deployment, too. PTCA was clinically successful in 178 (90.8%) pts, suboptimal result and/or MACE (AMI, emergency PTCA or CABG, fatal outcome) occurred in 18 (9.2%) cases. Due to unsuccessful PTCA-s, 3 (1.5%) pts underwent acute, 3 elective bypass surgery, in 1 (0.5%) case thoracal sympathectomy without revascularisation, in 1 no further intervention was done. The in-hospital as well as the 30 days mortality was 5 (2.6%). Taking into consideration the higher risk of CABG surgery at an old age, in the case of indication for coronary revascularisation the possibility of angioplasty should be considered first.

[Haemosuccus pancreaticus]

A case of haemosuccus pancreaticus is reported. A short description of the pathogenesis is also given. Bleeding from the pancreatic duct of the 40 year old male patient ensued as a complication of chronic pancreatitis and pseudocyst of the pancreas. Diagnosis was made by endoscopy, abdominal ultrasonography and angiography. Bleeding ceased spontaneously without surgical intervention.

[Surgical treatment of ischemic heart disease and unstable angina pectoris caused by intramyocardial descending coronary artery in a young patient]

Authors present a case report about the surgical management of a genetically predisposed ischemic heart disease occurred in young age with rare anatomical variation causing unstable angina pectoris. Besides the description the type of surgery, emphasis is made on the importance of whole scale cardiological investigations and--as in the described case--on the role of nearly ideal cooperation between the cardiologist and heart surgeon, which finally could prevent a larger size of myocardial infarction to occur.

[Results of amputation and rehabilitation]

Authors report on a questionnaire study of amputees having been rehabilitated in three departments of the National Institute of Medical Rehabilitation in 1988. The study was conducted one and a half years (average) after amputation. In comparison to an earlier study on a similar population the ratio of distal amputations has increased and the prosthetic fitting has improved. From these points results are well comparable with international standards. The feeling of isolation of the amputees has decreased since the earlier study. Their chance to get a job has deteriorated essentially, their subsistence problems have increased.

Nonneoplastic gonadal testosterone secretion as a cause of vaginal cell maturation in streak gonad syndrome

Endocrine studies were carried out on 3 patients with streak gonad syndrome, 2 of whom had slight proliferative vaginal smear patterns, and the 3rd had slight hirsutism with increased muscle mass but an atrophic type vaginal smear pattern. Simultaneous sampling of peripheral, adrenal and streak gonadal venous blood revealed mildly increased testosterone secretion by the streaks in the 2 patients who had proliferative cytohormonal patterns. Histologic examination of their streak gonads showed hilus cell hyperplasia. It might be suggested that hilus cell hyperplasia was the source of the increased testosterone secretion in these 2 patients and thus resulted in slight maturation of the vaginal epithelium.

Hypoadrenia following adrenal venography in Cushing's disease

Three patients with Cushing's disease are reported. In two patients the hyperfunction of the adrenal glands ceased following selective adrenal venography, moreover hypoadrenia has developed. In the third case necrosis following venography was proved by surgery and confirmed by histology. Regarding the therapeutic possibilities of Cushing's disease the use of this diagnostic procedure is taken into consideration but not recommended.

Atrial reentry in chronic repetitive supraventricular tachycardia

Atrial reentrance as a mechanism of the tachycardia was demonstrated in a 28-year-old patient suffering from chronic repetitive supraventricular tachycardia. Criteria for diagnosis included the following: (1) Repetitive supraventricular tachycardia was induced and terminated by properly timed atrial extrastimuli. (2) Return cycles of all atrial extrastimuli not abolishing the tachycardia were fully compensatory. (3) A-H prolongation was not a prerequisite to induce the tachycardia. (4) The contours of P and A waves during tachycardia differed from those in sinus rhythm, but atrial activation remained antegrade. (5) A concealed anomalous pathway could not be proved.

[Examination of antibiotic sensitivity/resistancy relations of strains of staphylococcus aureus haemolyticus originating from osteomyelitic patients (author's transl)]

On the basis of bacteriology results of osteomyelitic patients of the recent 10 year period the authors examined the changes of antibiotic sensitivity/resistancy relations of strains of coagulase positive Staphylococcus aureus haemolyticus. Examination of 385 strains of Staphylococci showed that Staphylococci originating from osteomyelitic patients are more sensitive, respectively in a lesser degree resistant to antibiotics than those of miscellaneous origin. Concerning 8, in everyday practice most commonly used antibiotics, by means of regression trend line analysis, it has been stated that in the period of 1966-1975 years Staphylococci originating from osteomyelitic patients show a decreasing resistancy to antibiotics examined. The authors are of the opinion that in osteomyelitic patients the no satisfactory results and the high number of recurrent inflammations are not attributable to resistant strains of Staphylococci, but are due to many other biologic factors.