Sherif Khattab

Metformin reduces abortion in pregnant women with polycystic ovary syndrome.

Background. Women with polycystic ovary syndrome (PCOS) are considered to be at increased risk of miscarriage. Since metformin has beneficial effects on the risk factors contributing to first-trimester abortion in PCOS patients, we hypothesized that metformin – owing to its metabolic, endocrine, vascular and anti-inflammatory effects – may reduce the incidence of first-trimester abortion in PCOS women. Materials and methods. A prospective cohort study was set up to determine the beneficial effects of metformin on PCOS patients during pregnancy. Two hundred non-diabetic PCOS patients were evaluated while undergoing assisted reproduction. One hundred and twenty patients became pregnant while taking metformin, and continued taking metformin at a dose of 1000–2000 mg daily throughout pregnancy. Eighty women who discontinued metformin use at the time of conception or during pregnancy comprised the control group. Results. Both groups were similar with respect to all background characteristics (age, body mass index, waist/hip ratio, follicle-stimulating hormone, luteinizing hormone, estradiol and dehydroepiandrosterone sulfate levels). Rates of early pregnancy loss in the metformin group were 11.6% compared with 36.3% in the control group (p < 0.0001; odds ratio = 0.23, 95% confidence interval 0.11–0.42). Conclusions. Administration of metformin throughout pregnancy to women with PCOS was associated with a marked and significant reduction in the rate of early pregnancy loss.

Can dopamine agonists reduce the incidence and severity of OHSS in IVF/ICSI treatment cycles? A systematic review and meta-analysis

BACKGROUND Recently, dopamine agonists were proposed as a prophylactic treatment for ovarian hyperstimulation syndrome (OHSS) in women at high risk in IVF/ICSI treatment cycles. METHODS We conducted a systematic review and meta-analysis of randomized trials comparing the prophylactic effect of the dopamine agonist, cabergoline, versus no treatment in IVF/ICSI cycles. Primary outcome was OHSS incidence per randomized woman. Secondary outcomes were live birth rate, ongoing pregnancy rate, clinical pregnancy rate and miscarriage rate. Searches (until September 2009) were conducted in MEDLINE, EMBASE, Science Direct, Cochrane Library and databases of abstracts. RESULTS Four randomized trials entailing 570 women were included. There was evidence of a statistically significant reduction in the incidence of OHSS in the cabergoline group (OR 0.41, 95% CI 0.25-0.66) with an absolute risk reduction of 12% (95% CI 6.1-18.2%), but there was no statistically significant evidence of a reduction in severe OHSS (OR 0.50, 95% CI 0.20-1.26). There was no evidence for a difference in clinical pregnancy rate (OR 1.07, 95% CI 0.70-1.62) and miscarriage rate (OR 0.31, 95% CI 0.03-3.07). CONCLUSION Prophylactic treatment with the dopamine agonist, cabergoline, reduces the incidence, but not the severity of OHSS, without compromising pregnancy outcomes.

Roaming honeypots for mitigating service-level denial-of-service attacks

Honeypots have been proposed to act as traps for malicious attackers. However, because of their deployment at fixed (thus detectable) locations and on machines other than the ones they are supposed to protect, honeypots can be avoided by sophisticated attacks. We propose roaming honeypots, a mechanism that allows the locations of honeypots to be unpredictable, continuously changing, and disguised within a server pool. A (continuously changing) subset of the servers is active and providing service, while the rest of the server pool is idle and acting as honeypots. We utilize our roaming honeypots scheme to mitigate the effects of service-level DoS attacks, in which many attack machines acquire service from a victim server at a high rate, against back-end servers of private services. The roaming honeypots scheme detects and filters attack traffic from outside a firewall (external attacks), and also mitigates attacks from behind a firewall (internal attacks) by dropping all connections when a server switches from acting as a honeypot into being active. Through ns-2 simulations, we show the effectiveness of our roaming honeypots scheme. In particular, against external attacks, our roaming honeypots scheme provides service response time that is independent of attack load for a fixed number of attack machines.

Proactive server roaming for mitigating denial-of-service attacks

We propose a framework based on proactive server roaming to mitigate the effects of denial-of-service (DoS) attacks. The active server proactively changes its location within a pool of servers to defend against unpredictable and undetectable attacks. Only legitimate clients can follow the active server as it roams. We present algorithms that are secure, distributed, randomized, and adaptive for triggering the roaming and determining the next server to roam to. We propose some modifications to the state recovery process of existing TCP connection-migration schemes to suit roaming. Preliminary experiments in a FreeBSD network show that the overhead of server roaming is small, in terms of response time, in the absence of attacks. Further, during an attack, roaming significantly improves the response time.

Can metformin reduce the incidence of gestational diabetes mellitus in pregnant women with polycystic ovary syndrome? Prospective cohort study

Background. Women with polycystic ovary syndrome (PCOS) are at a high risk to develop Gestational Diabetes mellitus (GDM). We hypothesized that metformin due to its metabolic, endocrine, vascular, and anti-inflammatory effects may reduce the incidence of GDM in PCOS women. Patient and method. We carried out a prospective cohort study to determine the beneficial effects of metformin on PCOS patients during pregnancy. Three-hundred and sixty non-diabetic PCOS patients were included who were conceived on metformin by different treatment modalities. Two-hundred pregnant women continued on metformin at a dose of 1000–2000 mg daily throughout pregnancy (study group) and 160 women discontinued metformin use at the time of conception (control group). Results. There is a statistically significant reduction in the incidence of GDM in favor of metformin group (OR: 0.17, 95% CI: 0.07–0.37). There is a statistically significant reduction in the incidence of pre-eclampsia in favor of metformin group (OR: 0.35, 95% CI: 0.13–0.94). Conclusion. Metformin is a promising medication for the prevention or reduction of the incidence of GDM and pre-eclampsia in PCOS women.

Jamming Mitigation in Multi-Radio Wireless Networks: Reactive or Proactive?

Jamming is a serious security problem in wireless networks. Recently, software-based channel hopping has received attention as a jamming countermeasure. In particular, proactive, or periodic, channel hopping has been studied more extensively than reactive hopping. In this paper, we address the question of which of the two defense strategies, namely proactive and reactive channel-hopping, provides better jamming resiliency than the other? in the context of single-and multi-radio wireless devices. In the single-radio context, we develop theoretical models to analyze the blocking probability for combinations of defense and attack strategies. In the multi-radio setting, we formulate the jamming problem as a max-min game and show through simulation that the game outcome depends on the payoff function. Our results show that reactive defense provides better jamming tolerance than proactive when considering communication availability. However, both reactive and proactive defenses have almost the same performance when energy efficiency is considered as a performance metric.

Live Baiting for Service-Level DoS Attackers

Denial-of-service (DoS) attacks remain a challenging problem in the Internet. By making resources unavailable to intended legitimate clients, DoS attacks have resulted in significant loss of time and money for many organizations, thus, many DoS defense mechanisms have been proposed. In this paper we propose live baiting, a novel approach for detecting the identities of DoS attackers. Live baiting leverages group-testing theory, which aims at discovering defective members in a population using the minimum number of dasiadasiatestspsilapsila. This leverage allows live baiting to detect attackers using low state overhead without requiring models of legitimate requests nor anomalous behavior. The amount of state needed by live baiting is in the order of number of attackers not number of clients. This saving allows live baiting to scale to large services with millions of clients. We analyzed the coverage, effectiveness (detection time, false positive and false negative probabilities), and efficiency (memory, message overhead, and computational complexity) of our approach. We validated our analysis using NS-2 simulations modeled after real Web traces.

Modeling of the channel-hopping anti-jamming defense in multi-radio wireless networks

Multi-radio (multi-interface, multi-channel) 802.11 and sensor networks have been proposed to increase network capacity and to reduce energy consumption, to name only a few of their applications. They are vulnerable, however, to jamming attacks, in which attackers block communication by radio interference or MAC-protocol violation. Two jamming countermeasures have been proposed, namely software-based channel hopping and error-correcting codes. In this paper, we introduce the problem of maximizing network goodput under jamming attacks through a combination of channel hopping and error-correction coding. We describe the solution space and investigate one point thereof, namely reactive defense against scanning attack. We develop a Markovian model of the reactive channel-hopping defense against the scanning jamming attack and validate it using simulation experiments. Our results suggest that an adaptive defense, based on our model, would improve the resiliency of multi-radio networks against jamming.

A simulation study of the proactive server roaming for mitigating denial of service attacks

The main goal of the NETSEC project is to design and implement a framework for mitigating the effects of the node-based and link-based denial of service (DoS) attacks. Our strategy employs three lines of defense. The first line of defense is to restrict the access to the defended services using offline service subscription, encryption and other traditional security techniques. The second line of defense is server roaming, by which we mean the migration of the service from one server to another, where the new server has a different IP address. Finally, each server and firewall(s) implement resource management schemes as a third line of defense. For example, deploying separate input queues to allocate different classes of service requests. We show our simulation study on the second line of defense, the server roaming. The design and procedure of the sever roaming on the NS2 is described. The promising results of applying the server roaming to mitigate the DoS attack in the simulation are also shown with analysis.

Use of metformin for prevention of ovarian hyperstimulation syndrome: a novel approach

In the present study, which includes 287 participants, metformin has been used by women undergoing IVF/intracytoplasmic sperm injection for more than 5 weeks before and during treatment and during luteal phase. There was no significant difference in number of gonadotrophins used, days of stimulation, number of oocytes retrieved, and number of embryos replaced. There was no significant difference in clinical pregnancy rate between both groups but there was significant reduction in the incidence of ovarian hyperstimulation syndrome (OHSS) in the group taking metformin. Metformin is a safe, cheap drug that can help in prevention of OHSS.