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This study was designed to study the individual or combined effects of estrogen and bipedal stance "exercise" on the lumbar vertebral body (LVB) and femoral neck (FN). At 6 months of age, six rats were sacrificed as baseline controls and all the others were either bilateral sham-ovariectomized or ovariectomized (OVX). Groups of OVX rats were housed in normal height cage (NC, 28 cm) or raised height cages (RC, 33 cm) and received biweekly s.c. injections of 10 microg/kg 17 beta estradiol (E2) or vehicle for 4 and 8 weeks. Histomorphometric measurements were performed on the undecalcified mid-transverse sections of the 4th LVB and FN. Ovariectomy alone induced cancellous bone loss by 21% and 39% in the LVB and FN, respectively; intracortical porosity area of the FN increased by 108% while total bone area did not change significantly because of the periosteal expansion following OVX. E2 alone partially prevented cancellous bone loss in the LVB and FN and prevented increased intracortical porosity area in the FN by reducing eroded surface and activation frequency. RC alone partially prevented the decrease of cancellous bone in the LVB and FN by reducing the bone-eroded surface but increased wall width. E2 plus RC completely preserved cancellous bone by having an additive effect on reducing eroded surface and activation frequency. RC helped to partially prevent decreased periosteal bone formation after estrogen administration. In conclusion, apart from inducing cancellous bone loss in the LVB and FN, OVX also increased intracortical remodeling in the FN. Estrogen prevented the overall activation of remodeling space induced by OVX. Apart from having similar effects as estrogen on remodeling space, RC induced positive bone balance within each remodeling unit. Combination treatment increased total bone mass beyond that of sham-control level by having an additive effect on lowering bone remodeling and increasing wall in both the LVB and FN.

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The construction of the multi-focal Veselago lens predicted earlier is proposed on the basis of a uniaxial photonic crystal consisting of cylindrical air holes in silicon that make a triangular lattice in a plane perpendicular to the axis of the crystal. The object and image are in air. The period of the crystal should be 0.44µm to work at the wavelength 1.5µm. The lens does not provide superlensing but the half-width of the image is 0.5λ. The lens is shown to have wave guiding properties depending on the substrate material. PACS numbers: 78.20.Ci,41.20.Jb, 42.25.-p 1 1.INTRODUCTION A left handed medium (LHM), defined by Veselago[1] as a medium with simultaneously negative µ and ǫ, has recently attracted much attention mostly because of negative refraction at its interface with a regular medium (RM). This effect allows creation of a unique device called the Veselago lens. This lens is a slab of a LHM embedded inside a RM with the condition that both media have the same isotropic refractive index and the same impedance. It was shown recently[2, 3] that a two-dimensional (2D) dielectric uniaxial photonic crystal (PC) made of non-magnetic materials can behave as a LHM with negative ǫ and µ if it has a negative group velocity in the vicinity of the Γ-point of the second Brillouin zone. Experimental demonstration of negative refraction in a metallic PC using the modes near the Γ-point has been presented in Ref. [4].Proximity to the Γ-point is crucial for the PC-based LHM. In general, ǫ and µ of a PC are functions not only of ω, but also of k. It has been shown[2] that, in the vicinity of the Γ-point, ǫ, µ, and ω are functions of k. Therefore, for every propagating mode, k, ǫ, and µ can be represented as a function of ω. However, the parameters ǫ(ω) and µ(ω) are a property of a given mode in the medium rather than a property of the whole medium. It is shown [5,6] that parameters ǫ and µ for evanescent waves (EW's) in the same medium and at the same frequency strongly depend on k.We think now that the 2D PC with a square lattice considered in Ref. [2,5,6] is a wrong choice from a practical point of view. Although both µ and refractive index n are zero [2] exactly at the Γ-point, one should still work near the Γ-point where the parameters ǫ, µ, and ω are isotropic. In the square lattice the maximum value of n that can be achieved in the isotropic region is about 0.33. For the Veselago lens, the LHM and the RM should have the same value of n and it would be difficult to find a transparent RM with such a low n. The situation is much better for the 2D lattice with hexagonal symmetry in the plane (triangular lattice shown in Fig. 1(a)) because the width of the isotropic region near the Γ-point is much wider. Wang et al. [7] were the first to find out computationally that n = 1 can be reached in the isotropic region of the hexagonal (triangular) lattice. Their result can be explained from symmetry. For both square and triangular lattices, the expansions of frequency near the Γ-point have the same form up to the quadratic term...

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