Comment on: “Dynamical analysis of Cohen-Grossberg neural networks with distributed delays” [Phys. Lett. A 364 (2007) 38]

It is pointed out that an unnatural assumption is made in the following Letter [Z. Mao, H. Zhao, Phys. Lett. A 364 (1) (2007) 38]. Therefore, the results of the Letter are not relevant to the real Cohen-Grossberg neural network model.     

Reply to: “Comment on: ‘Epidemic spreading on heterogeneous networks with identical infectivity’ [Phys. Lett. A 364 (2007) 189]” [Phys. Lett. A 372 (2008) 1722]

In a recent Letter [R. Yang, B.H. Wang, J. Ren, W.J. Bai, Z.W. Shi, W.X. Wang, T. Zhou, Phys. Lett. A 364 (2007) 189], we proposed a modified susceptible-infected-recovered (SIR) model, in which each node is assigned with an identical capability of active contact, A, at each time step. We found a threshold value λc=1/A in uncorrelated and unlocalized networks. A corresponding Comment, raised by Alberto d'Onofrio, claimed that (i) our model is not biologically relevant; (ii) our model does not have a threshold behavior for recovered population; (iii) the analytical result λc=1/A is incorrect being considered as a threshold for epidemic outbreak, because of an improper approximation of the initial configuration. In this Reply, I show that, by debating from point to point, our analysis and conclusion are solid and reasonable.     

Comment on: “Synchronization of two chaotic nonlinear gyros using active control” [Phys. Lett. A 343 (2005) 153]

A modification to the control law presented in [Y. Lei, W. Xu, H. Zheng, Synchronization of two chaotic nonlinear gyros using active control, Phys. Lett. A 343 (2005) 153] is proposed.     

Comment on: “Construction of bound entangled edge states with special ranks” [Phys. Lett. A 359 (2006) 603]

Recently, Clarisse [L. Clarisse, Phys. Lett. A 359 (2006) 603] and Ha [K.-C. Ha, Phys. Lett. A 361 (2007) 515] found examples of types (5,5) and (6,6) entangled states with positive partial transposes. In this Letter, we show that their examples have the Schmidt number as 2.     

Comment on: “Construction of bound entangled edge states with special ranks” [Phys. Lett. A 359 (2006) 603]

In a Letter by Clarisse [L. Clarisse, Phys. Lett. A 359 (2006) 603–607] the open problem of the existence of (5,5)$(5,5)$ and (6,6)$(6,6)$ PPT edge states has been solved. Here we report the existence of another large class of (5,5)$(5,5)$ entangled edge states with positive partial transposes. We also give a PPT edge state with range dimensions (6,6)$(6,6)$.     

Erratum to: “Comment on: ‘Electromagnetic wave propagation in single-wall carbon nanotubes’ [Phys. Lett. A 333 (2004) 303]” [Phys. Lett. A 364 (2007) 515]

Here we plot the correct form of Fig. 2 in [H. Khosravi, A. Moradi, Phys. Lett. A 364 (2007) 515].     

Comment on: “Dynamical analysis of Cohen-Grossberg neural networks with continuously distributed delays” [Phys. Lett. A 364 (2007) 38]

Recently, Mao and Zhao [Z. Mao, H. Zhao, Phys. Lett. A 364 (2007) 38] considered the existence and uniqueness of the equilibrium point of the Cohen-Grossberg neural network model with continuously distributed delays. Mao and Zhao established Theorem 1. In this Letter, we would like to point out that Theorem 1 given by Mao and Zhao is incorrect in general.     

Comment on: “Dense coding and teleportation with one-dimensional cluster states” [Phys. Lett. A 364 (2007) 7]

The schemes on quantum dense coding and teleportation [Phys. Lett. A 364 (2007) 7] are revisited. By reformulizing one-dimensional n-qubit cluster states, we decompose the necessary multi-qubit collective unitary operation into a sequence of single-qubit Hadamard (H) and two-qubit controlled-not (C) operations. Our reduction makes the schemes feasible today.     

Comment on: “Spherical Kadomtsev–Petviashvili equation and nebulons for dust ion-acoustic waves with symbolic computation” [Phys. Lett. A 340 (2005) 243]

Tian and Gao [B. Tian, Y.T. Gao, Phys. Lett. A 340 (2005) 243] have recently constructed a spherical Kadomtsev–Petviashvili equation for the dust-ion-acoustic waves with zenith-angle perturbation in a cosmic dusty plasma, and symbolically obtained and discussed spherical structures of the expanding dark, shrinking dark, expanding bright and shrinking bright nebulons. In this Comment, we point out that certain simple coordinate transformations exist, which make the analytic nebulon solutions more easily accessible. We also show that the transformed solutions can result in a couple of nebulon solutions in addition to the second-order nebulons found by Tian and Gao.     

Comment on: “A simple chaotic delay differential equation” [Phys. Lett. A 366 (2007) 397]

The purpose of this Letter is to give the reference for the model proposed in the discussion section of the above paper [J.C. Sprott, Phys. Lett. A 366 (2007) 397] and to show that chaotic behavior of this model has been studied in [A. Uçar, Int. J. Eng. Sci. 40 (2002) 251; A. Uçar, Chaos Solitons Fractals 16 (2003) 187].     

Comment on: “A class of bound entangled states” [Phys. Lett. A 352 (2006) 321]

We generalize the condition keeping the special states bound entangled [S.-M. Fei, X. Li-Jost, B.-Z. Sun, Phys. Lett. A 352 (2006) 321] to the general states. Taking the original 4×4$4\times 4$ states as 2×8$2\times 8$ states we show that they still can be bound entangled.     

Reply to: “Comment on: ‘Efficient high-capacity quantum secret sharing with two-photon entanglement’ [Phys. Lett. A 372 (2008) 1957]” [Phys. Lett. A 373 (2009) 396]

A corresponding Comment, raised by Yang and Wen, claimed that (i) our scheme cannot complete the task of secret sharing well even if the agents obtain the information about their measuring bases; (ii) they give a feasible improvement of our protocol. In this Reply, we show that their first judgment is wrong and their improvement is insecure.     

Comment on: “Series solution to the Thomas-Fermi equation” [Phys. Lett. A 365 (2007) 111]

We discuss a recently proposed analytic solution to the Thomas-Fermi (TF) equation and show that earlier approaches provide more accurate results. In particular, we show that a simple and straightforward rational approximation to the TF equation yields the slope at origin with unprecedented accuracy, as well as remarkable values of the TF function and its first derivative for other coordinate values.     

Comment on: “Electromagnetic wave propagation in single-wall carbon nanotubes” [Phys. Lett. A 333 (2004) 303]

In a recent article [L. Wei, Y.-N. Wang, Phys. Lett. A 333 (2004) 303], Li Wei and You-Nian Wang studied the propagation of electromagnetic wave in single-wall carbon nanotubes and presented different expressions of the dispersions relations of TE and TM modes, respectively. Here we have derived the correct form of the dispersion relation for TM mode on low-frequency electromagnetic wave. It is shown numerically that asymptotic behaviours of the TM and TE modes are quite similar in single-wall carbon nanotubes.     

Comment on: “Photoionization of helium-like ions in asymptotic non-relativistic region” [Phys. Lett. A 358 (2006) 211]

The results of Mikhailov et al. [A.I. Mikhailov, A.V. Nefiodov, G. Plunien, Phys. Lett. A 358 (2006) 211] on single and double ionization of He at high energy can be obtained quite simply by combining two previous results long well known in the literature. The results of Mikhailov et al. can also be understood in a larger context, using an asymptotic Fourier transform approach, which also allows a justification of various statements assumed but not demonstrated by Mikhailov et al.     

Comment on: “Epidemic spreading on heterogeneous networks with identical infectivity” [Phys. Lett. A 364 (2007) 189]

In [R. Yang, et al., Phys. Lett. A 364 (2007) 189], it has been introduced a network-based Kermack-McKendrick-like SIR epidemic model, in which each node shows an identical capability of contact A and in which it has been claimed that, on scale free networks, the value A⁻¹ would be a threshold value for the density of recovered individuals. We show here that the recovered individuals cannot follow the claimed threshold behaviour. Furthermore, we give a biologically sound threshold ruling the transitory dynamics of the epidemics.     

Comment on: “Three-party quantum secure direct communication based on GHZ states” [Phys. Lett. A 354 (2006) 67]

The GHZ-state-based quantum secure direct communication (QSDC) protocol [X.-R. Jin, et al., Phys. Lett. A 354 (2006) 67] and its improved version [Z. Man, Y. Xia, Chin. Phys. Lett. 24 (2007) 15] are analyzed from the aspect of security. It shows that much information of the transmitted secret message will be leaked out in both protocols.