Significance of lignin and fungal markers in the Devonian (407 Ma) Rhynie Chert.

The Rhynie Chert (Lower Devonian, Scotland) hosts a remarkably well-preserved early terrestrial ecosystem. Organisms including plants, fungi, arthropods, and bacteria were rapidly silicified due to inundation by silica-rich hot spring fluids. Exceptional molecular preservation has been noted by many authors, including some of the oldest evidence of lignin in the fossil record.

Horizontal magnetic tweezers and its applications in single molecule micromanipulation experiments.

Magnetic tweezers (MTs) have become indispensable tools for gaining mechanistic insights into the behavior of DNA-processing enzymes and acquiring detailed, high-resolution data on the mechanical properties of DNA. Currently, MTs have two distinct designs: vertical and horizontal (or transverse) configurations. While the vertical design and its applications have been extensively documented, there is a noticeable gap in comprehensive information pertaining to the design details, experimental procedures, and types of studies conducted with horizontal MTs.

Himalayan watersheds in Nepal record high soil erosion rates estimated using the RUSLE model and experimental erosion plots.

The rising unpredictability in the food supply chain in many parts of the world is related to soil loss and poor agricultural output. The Revised Universal Soil Loss Equation (RUSLE), widely used for estimating soil loss, was applied in the western mid-hills in Nepal, with steep slopes and fragile geology. This region is at high risk for rapid soil erosion and mass wasting.

Prevalence of hypothyroidism in pregnancy: An epidemiological study from 11 cities in 9 states of India.

Background: A previous hospital based study from Delhi revealed a high prevalence of hypothyroidism in pregnant women. Several other studies with small sample size also indicate a rising trend of prevalence of hypothyroidism during pregnancy in India.

Objective: To assess prevalence of hypothyroidism in pregnant women from various states/cities across India.

Reciprocity constraints on the matrix of reflection from optically anisotropic surfaces.

We derive certain constraints on the reflection matrix for reflection from a plane, nonmagnetic, optically anisotropic surface using a reciprocity theorem stated long ago by Van de Hulst [Light Scattering by Small Particles (Wiley, 1957)] in the context of scattering of polarized light. The constraints are valid for absorbing and chiral media and can be used as tools to check the consistency of derived expressions for such matrices in terms of the intrinsic parameters of the reflecting medium as illustrated by several examples.

Cancellation of simple optical anisotropies without use of a Faraday mirror.

We first derive the round-trip Jones matrix for double passage through a reciprocal optical medium by means of reflection off a plane mirror that could be optically anisotropic. We then show that if a medium with only linear birefringence and linear dichroism is placed between a pair of orthogonal quarter-wave plates with principal axes at 45 degrees to that of the medium and the sandwich is placed in front of an isotropic mirror it behaves, under double passage, like an isotropic medium. We describe a simple liquid crystal device that behaves, in reflection, as an isotropic medium whose refractive index can be varied by application of an electric field, thus acting as a phase only modulator for light in any polarization state.

Transpose symmetry of the Jones matrix and topological phases.

The transmission Jones matrix of an arbitrary stack of reciprocal plane-parallel plates that has been turned through 180 degrees about an axis in the plane of the stack is, in an appropriate basis, the transpose of the transmission matrix of the unturned slab with a change in the sign of the off-diagonal elements. We prove this convention-free result for the case where reflection at the interfaces can be ignored and use it to devise an experimental scheme to separate isotropic and topological phase changes in a reciprocal optical medium.

Observable Dirac-type singularities in Berry's phase and the monopole.

A three-dimensional generalization of the sign-change ( pi phase shift) rule for adiabatic cycles of spin-1/2 or two-state wave functions encircling a degeneracy in the parameter space of the Hamiltonian yields a Dirac-type singularity wherein any closed circuit of the adiabatic cycle in which the degeneracy is "looped" results in an observable +/-2pi phase shift. It is concluded that an interferometer loop similarly taken around a magnetic monopole of strength n/2 yields an observable +/-2npi phase shift, n being an integer.