Impact of network topology on the stability of DC microgrids.

We probe the stability of Watts-Strogatz DC microgrids, in which droop-controlled producers and constant power load consumers are homogeneously distributed and obey Kirchhoff's circuit laws. The concept of survivability is employed to evaluate the system's response to Dirac-delta voltage perturbations at single nodes. A fixed point analysis of the power grid model yields that there is only one relevant attractor. Using a set of simulations with random networks, we investigate correlations between survivability and three topological network measures: the share of producers in the network and the degree and the average neighbor degree of the perturbed node. Depending on the imposed voltage and current limits, the stability is optimized for low node degrees or a specific share of producers. Based on our findings, we provide an insight into the local dynamics of the perturbed system and derive explicit guidelines for the design of resilient DC power grids.

[Loco-regional block in ophthalmic surgery: single drug or drug combination with hyaluronidase? Randomized prospective study]. / Blocchi loco-regionali in oculistica: monofarmacologici o miscela con jaluronidasi? Studio prospettico randomizzato.

UNLABELLED: The aim of this study is the comparison between the use of bupivacaine alone and a mixture of bupivacaine, mepivacaine and hyaluronidase in both retrobulbar and peribulbar blockades for eye surgery. Three hundred ninety-nine consecutive adult patients scheduled for cataract surgery with regional anaesthesia were included in this prospective, randomized and partially blind study. Peribulbar blockade was performed on 199 patients (group P). Ninety-nine of them received a mixture of local anaesthetics and hyaluronidase (sub-group M), while 100 received bupivacaine alone (sub-group B). Retrobulbar blockade was performed on 200 patients (group R): 100 of them received the mixture with hyaluronidase (sub-group M), while 100 received bupivacaine (sub-group B). The interval between anaesthesia and motor blockade (onset time), the presence of residual ocular movements, the need of further anaesthesia, the quality of anaesthesia, the ocular tone, the length of anaesthesia and possible complications were registered. RESULTS: Retrobulbar blockade has the only advantage of a shorter onset time, while peribulbar blockade shows a longer anaesthetic effect. Mixture with hyaluronidase (the sub-group M) has a shorter onset time, a lesser need of further anaesthesia, fewer residual ocular movements and a better quality of anaesthesia. CONCLUSIONS: Local anaesthetics mixture with hyaluronidase associated with peribulbar blockade presents the advantages of rapidity, duration and better quality without the risks of retrobulbar blockade side effects.

Circadian temperature and activity rhythms in unmedicated narcoleptic patients.

Fifteen unmedicated narcoleptic patients with and without sleep-onset REM period (SOREMP) were compared with 16 unmedicated, age-and-sex-matched control subjects with respect to polygraphic, core body temperature and motor activity recordings. Whereas narcoleptic patients with SOREMPs had significantly more quiet wakefulness during sleep, those without SOREMPs had significantly more quiet wakefulness during daytime than the other groups. Compared with that of controls, temperature of both narcoleptic groups showed (a) less rise of temperature curve in the morning, (b) dampening of temperature amplitude, (c) phase advance of acrophase, and (d) advance of temperature minimum after sleep onset. Maximal temperature decline occurred earlier in patients with SOREMPs during naps and sleep than in the other groups. We could confirm parallels between temperature and motor activity with controls and found no change in the oscillator of narcoleptic patients. Advanced temperature minima and first REMPs relative to sleep onset and maximal temperature decline occurring nearer to sleep onset indicate a defect in the temperature-locked triggering of REM in narcoleptic patients with SOREMP and a circadian rhythm disorder.

Forensic pathology's dilemma: state death certificate.

Forensic pathologists are familiar with the intricacies and importance of death certificates. But Pennsylvania physicians also need an updated, working knowledge of these vital documents. Members of the PMS Resident Physician Section have urged the State Society to support guidelines to help "clean up" the errors.