Cost Optimization in SIS Model of Worm Infection

Recently, there has been a constant barrage of worms over the Internet. Besides threatening network security, these worms create an enormous economic burden in terms of loss of productivity not only for the victim hosts, but also for other hosts, as these worms create unnecessary network traffic. Further, measures taken to filter these worms at the router level incur additional network delays because of the extra burden placed on the routers. To develop appropriate tools for thwarting the quick spread of worms, researchers are trying to understand the behavior of worm propagation with the aid of epidemiological models. In this study, we present an optimization model that takes into account infection and treatment costs. Using this model we can determine the level of treatment to be applied for a given rate of infection spread.     

Study of the surface layer of ground high strength steels

Grinding is one of the most widely used finishing operations to obtain close tolerances and a reasonably good surface finish. The effects of rough grinding on different types of steels both hardened and unhardened have been studied. Most of the surface defects caused by extremely abusive conditions were produced by rough grinding. The effects of gentle and conventional conditions of grinding were also studied for comparative data.     

Data Masking: A New Approach for Steganography?

It is well known that encryption provides secure channels for communicating entities. However, due to lack of covertness on these channels, an eavesdropper can identify encrypted streams through statistical tests and capture them for further cryptanalysis. Hence, the communicating entities can use steganography to achieve covertness. In this paper we propose a new form of multimedia steganography called data masking. Instead of embedding a secret message into a multimedia object, as in traditional multimedia steganography, we process the entire secret message to make it appear statistically similar to a multimedia object itself. Thereby we foil an eavesdropper who is primarily applying statistical tests to detect encrypted communication channels. We show that our approach can potentially give a covert channel capacity which is an order of magnitude higher than traditional steganography. Our experiments also show that steganalyzers trained with stego objects of known steganographic have a low detection accuracy for datamasked multimedia objects.     

Speech perception in children after cochlear implantation

Impaired endothelium-dependent vasodilation has been reported to play an important role in the pathogenesis of cardiovascular diseases such as coronary artery disease (CAD) and congestive heart failure (CHF). However, the precise mechanism of endothelial dysfunction has not been elucidated in these conditions. To evaluate the role of oxidative stress in endothelial dysfunction, the effect of antioxidant ascorbic acid on brachial flow-mediated, endothelium-dependent vasodilation during reactive hyperemia and nitroglycerin-induced endothelium-independent vasodilation was examined with high resolution ultrasound in 12 patients with CHF caused by idiopathic dilated cardiomyopathy without established coronary atherosclerosis and in 10 patients with CAD. Flow-mediated vasodilation in CHF (4.4+/-0.5%) and CAD (4.0 - 0.8%) was significantly (p <0.05) attenuated compared with that in 10 control subjects (9.6+/-0.9%). However, nitroglycerin-induced vasodilation was similar in 3 groups (13.7+/-1.3% in control, 13.9+/-1.1% in CHF, 12.7+/-1.4% in CAD). Ascorbic acid could significantly improve flow-mediated vasodilation only in patients with CAD (9.1+/-0.9%) but not with CHF (5.6+/-0.6%), and had no influence on nitroglycerin-induced vasodilation (13.6+/-1.1% in CHF, 14.0+/-1.3% in CAD). These results suggest that, in brachial circulation, augmented oxidative stress mainly leads to endothelial dysfunction in CAD but not in CHF caused by idiopathic dilated cardiomyopathy.     

The blending of competitive and regulatory strategies: a second opinion

A comparison of the 10 states that as of 30 June 1994 witnessed the highest and lowest percent of health maintenance organization market penetration, and the findings reported in the Dartmouth Atlas of Health Care in the United States, both illustrate dramatic differences among the various states in the distribution, utilization, and cost of hospital and other health services. This article thereafter focuses on the implications of these findings in the context of the states eventually blending competitive and regulatory strategies to constrain hospital expenditures-a conceptual framework that is consistent with Americans being advocates of pluralism when organizing and financing their health care system.     

Cerebral serotonergic neurons reciprocally modulate swim and withdrawal neural networks in the mollusk Clione limacina

1. A pair of serotonin-immunoreactive neurons has been identified in the cerebral ganglia of the pteropod mollusk Clione limacina, which produce coordinated, excitatory/inhibitory effects on neurons controlling two incompatible behaviors, swimming and whole body withdrawal. These cells were designated cerebral serotonergic ventral (Cr-SV) neurons. 2. Activation of Cr-SV neurons produces a prominent inhibition of the pleural withdrawal neurons, which have been previously shown to induce whole body withdrawal in Clione. In addition, the cerebral neurons produce weak excitatory inputs to swim motor neurons, pedal serotonergic neurons involved in the peripheral modulation of swimming, and to the serotonergic heart excitor neuron. 3. Inhibitory and excitatory effects appear to be produced by serotonin because they are mimicked by exogenous serotonin and are blocked by the serotonin antagonist mianserin. 4. All serotonergic neurons identified thus far in the CNS of Clione appear to function in a coordinated manner, altering a variety of neural centers all directed toward the activation of swimming behavior.     

MR-monitored remitting-relapsing pattern of cortical involvement in Rasmussen syndrome: comparative evaluation of serial MR and PET/SPECT features

We report the serial MR and PET/SPECT findings in a 2 1/2-year-old boy presenting with Rasmussen syndrome and highlight the close qualitative correlations between the results of the imaging modality and the functional isotopic techniques. The latter demonstrated a wider field of extension of the disease process. Routine MRI demonstrated its ability to detect brain changes matching the more sensitive PET and SPECT data and correlated well with the clinical evolution.     

A thyrotropin-secreting pituitary adenoma as a cause of thyrotoxic periodic paralysis

We describe a patient with thyrotoxic periodic paralysis (TPP) caused by a thyrotropin-secreting pituitary adenoma. The diagnosis TPP was based on the combination of episodes of reversible hypokalaemic paralysis, hyperthyroidism and electrophysiological findings. A thyrotropin-secreting pituitary adenoma was diagnosed on the basis of endocrinological function tests and MRI of the pituitary gland. Before transsphenoidal resection of the adenoma, treatment with octreotide restored euthyroidism both clinically and biochemically. Immunocytochemistry of the pituitary adenoma was positive for TSH exclusively. Incubation with octreotide or quinagolide induced decreased TSH and alpha-subunit production by the cultured adenoma cells, in agreement with the pre-operative in vivo data. This paper is the first to describe in vivo and in vitro characteristics of a thyrotropin-secreting pituitary adenoma in a patient presenting with periodic paralysis.