Optimization of Information Rate Upper and Lower Bounds for Channels with Memory

We consider the problem of minimizing upper bounds and maximizing lower bounds on information rates of stationary and ergodic discrete-time channels with memory. The channels we consider can have a finite number of states, such as partial response channels, or they can have an infinite state-space, such as time-varying fading channels. We optimize recently-proposed information rate bounds for such channels, which make use of auxiliary finite-state machine channels (FSMCs). Our main contribution in this paper is to provide iterative expectation-maximization (EM) type algorithms to optimize the parameters of the auxiliary FSMC to tighten these bounds. We provide an explicit, iterative algorithm that improves the upper bound at each iteration. We also provide an effective method for iteratively optimizing the lower bound. To demonstrate the effectiveness of our algorithms, we provide several examples of partial response and fading channels, where the proposed optimization techniques significantly tighten the initial upper and lower bounds. Finally, we compare our results with an improved variation of the \emph{simplex} local optimization algorithm, called \emph{Soblex}. This comparison shows that our proposed algorithms are superior to the Soblex method, both in terms of robustness in finding the tightest bounds and in computational efficiency. Interestingly, from a channel coding/decoding perspective, optimizing the lower bound is related to increasing the achievable mismatched information rate, i.e., the information rate of a communication system where the decoder at the receiver is matched to the auxiliary channel, and not to the original channel.Comment: Submitted to IEEE Transactions on Information Theory, November 24, 200

The main transition in the Pink membrane model: finite-size scaling and the influence of surface roughness

We consider the main transition in single-component membranes using computer simulations of the Pink model [D. Pink {\it et al.}, Biochemistry {\bf 19}, 349 (1980)]. We first show that the accepted parameters of the Pink model yield a main transition temperature that is systematically below experimental values. This resolves an issue that was first pointed out by Corvera and co-workers [Phys. Rev. E {\bf 47}, 696 (1993)]. In order to yield the correct transition temperature, the strength of the van der Waals coupling in the Pink model must be increased; by using finite-size scaling, a set of optimal values is proposed. We also provide finite-size scaling evidence that the Pink model belongs to the universality class of the two-dimensional Ising model. This finding holds irrespective of the number of conformational states. Finally, we address the main transition in the presence of quenched disorder, which may arise in situations where the membrane is deposited on a rough support. In this case, we observe a stable multi-domain structure of gel and fluid domains, and the absence of a sharp transition in the thermodynamic limit.Comment: submitted to PR

Determination of Dioctyl phthalate (DEHP) concentration in polyvinyl chloride (PVC) plastic parts of toothbrushes

Phthalates are chemicals that are widely used in daily products and polyvinyl chloride (PVC) plastics, mainly because of their ability to enhance flexibility and durability. The presence of phthalates in various products contributes to the substantial exposure that all consumers may experience. Continuity in phthalate exposure has several side effects, including endocrine disruption, neurological damage, asthma, hormonal imbalances, obesity, infertility, genital defects, and testicular cancer. The purpose of this research experiment was to determine the Dioctyl phthalate (DEHP) concentration of PVC plastic parts of toothbrushes. The method used to conduct the experiment was Gas Chromatography/Mass Spectrometry. The result showed that the phthalate concentration of a Reach adult’s toothbrush and a Equate kid’s toothbrush were 1.97 ppm and 0.56 ppm respectively. Therefore, this study found that considerable concentrations of phthalates were also present in toothbrushes, which, due to consumers’ daily exposure, would certainly have negative effects on users’ health in the long term

Determination of Dioctyl phthalate (DEHP) concentration in polyvinyl chloride (PVC) plastic parts of toothbrushes

Phthalates are chemicals that are widely used in daily products and polyvinyl chloride (PVC) plastics, mainly because of their ability to enhance flexibility and durability. The presence of phthalates in various products contributes to the substantial exposure that all consumers may experience. Continuity in phthalate exposure has several side effects, including endocrine disruption, neurological damage, asthma, hormonal imbalances, obesity, infertility, genital defects, and testicular cancer. The purpose of this research experiment was to determine the Dioctyl phthalate (DEHP) concentration of PVC plastic parts of toothbrushes. The method used to conduct the experiment was Gas Chromatography/Mass Spectrometry. The result showed that the phthalate concentration of a Reach adult’s toothbrush and a Equate kid’s toothbrush were 1.97 ppm and 0.56 ppm respectively. Therefore, this study found that considerable concentrations of phthalates were also present in toothbrushes, which, due to consumers’ daily exposure, would certainly have negative effects on users’ health in the long term

Thermodynamics of string black hole with hyperscaling violation

In this paper, we start with black brane and construct specific space-time which violates hyperscaling. In order to obtain the string solution we apply Null-Melvin-Twist and $KK$-reduction. By using the difference action method we study thermodynamics of system to obtain Hawking-Page phase transition. In order to have hyperscaling violation we need to consider $\theta=\frac{d}{2}.$ In that case the free energy $F$ is always negative and our solution is thermal radiation without a black hole. Therefore we find that there is not any Hawking-Page transition. Also, we discuss the stability of system and all thermodynamical quantities.Comment: 12 pages. Accepted for publication in EPJ

What is the best imaging method for patients with a presumed acute stroke?

Evidence-based answer: It depends on whether the stroke is ischemic or hemorrhagic. For early detection of ischemic stroke, magnetic resonance imaging (MRI) using diffusion-weighted imaging (DWI) is highly sensitive and specific, whereas computed tomography (CT) is less sensitive but about as specific (strength of recommendation [SOR]: B, a meta-analysis of lower quality RCTs). MRI using DWI and CT are probably comparable for detecting acute hemorrhagic stroke (SOR: B, a cohort study). When thrombolysis is being considered and hemorrhage must be ruled out rapidly, either test is acceptable if it can be performed and interpreted within 45 minutes of patient arrival, although MRI typically costs about twice as much as CT (SOR: C, expert opinion)

Baryon Binding Energy in Sakai-Sugimoto Model

The binding energy of baryon has been studied in the dual $AdS_5\times S^5$ string theory with a black hole interior. In this picture baryon is constructed of a $D_5$ brane vertex wrapping on $S^5$ and $N_c$ fundamental strings connected to it. Here, we calculate the baryon binding energy in Sakai-Sugimoto model with a $D_4/D_8/\bar{D_8}$ in which the supersymmetry is completely broken. Also we check the $T$ dependence of the baryon binding energy. We believe that this model represents an accurate description of baryons due to the existence of Chern-Simones coupling with the gauge field on the brane. We obtain an analytical expression for the baryon binding energy . In that case we plot the baryon binding energy in terms of radial coordinate. Then by using the binding energy diagram, we determine the stability range for baryon configuration. And also the position and energy of the stable equilibrium point is obtained by the corresponding diagram. Also we plot the baryon binding energy in terms of temperature and estimate a critical temperature in which the baryon would be dissociated.Comment: 14 pages, 1 fi

Differences in Prevalence of Muscle Weakness (Sarcopenia) in Haemodialysis Patients Determined by Hand Grip Strength Due to Variation in Guideline Definitions of Sarcopenia

BACKGROUND: Muscle weakness is associated with increased mortality, and hemodialysis (HD) patients are at an increased risk for muscle loss. There is no agreed definition for muscle weakness, so we determined whether using different cut‐off criteria recommended by guideline groups altered the prevalence in HD patients. METHODS: We measured hand grip strength (HGS) in HD outpatients, comparing HGS with clinical guideline cut‐offs (European Working Group on Sarcopenia in Older People [EWGSOP] and North American Foundation for the National Institutes of Health Sarcopenia Project [FNIH]) used to define muscle wasting (sarcopenia) with age‐matched and gender‐matched normative data. RESULTS: We studied 459 patients, 61.4% male, 47.3% diabetic. The prevalence of muscle weakness was significantly different when measuring HGS; 84.5% using the EWGSOP cut‐off and 73.2% with FNIH criteria, and 75.2% using North American normative data and 56.6% U.K. normative data (P < .01). On logistic regression, muscle weakness was associated with age (odds ratio [OR] 1.05, P < .001), weight (OR 0.96, P < .001), serum albumin (OR 0.89, P = .007), and being nondiabetic (OR 0.31, P = .001). Of patients with no comorbidity, 66.7% were weak when compared with 93.8% with the highest comorbidity scores (P < .001). CONCLUSION: There is currently no agreed universal definition for sarcopenia, but the EWGSOP and FNIH advocate HGS cut‐offs as part of their definition. The prevalence of muscle weakness varies according to cut‐off and whether age‐matched and gender‐matched normative data are used. In addition, patient characteristics in terms of age and comorbidity determine the prevalence of muscle weakness

The effect of higher derivative correction on η/s\eta /s and conductivities in STU model

In this paper we study the ratio of shear viscosity to entropy, electrical and thermal conductivities for the R-charged black hole in STU model. We generalize previous works to the case of a black hole with three different charges. Actually we use diffusion constant to obtain ratio of shear viscosity to entropy. By applying the thermodynamical stability we recover previous results. Also we investigate the effect of higher derivative corrections.Comment: revised versio