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. This article aims to address this gap by providing a concise overview of the fundamental principles underlying transverse MTs. It will explore the multifaceted applications of this technique as an exceptional instrument for scrutinizing DNA and its interactions with DNA-binding proteins at the single-molecule level.

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. To estimate soil loss, this study utilized the RUSLE model with experimental erosion plots in the Aadhikhola and Tinahukhola watersheds, capturing real-time erosion in the field. The annual soil loss for the Aadhikhola watershed is estimated at ∼41.4 tons ha-1 yr-1. In contrast, in the Tinahukhola watershed, soil loss is low (∼24.1 tons ha-1 yr-1). Although annual rainfall showed an increasing trend in both watersheds, the change in soil loss was statistically insignificant. The high erosion rates from the experimental plots in both watersheds support the model outputs. Results from the experimental plots recorded the rate of soil erosion for different land use as: irrigated agricultural land > rainfed agricultural land > forests. The trends highlight the role of human activities in enhancing soil erosion in these mountainous terrains in terms of medium to long-term perspectives. Therefore, sustainable agriculture practices in these terrains must investigate alternate ways to decrease soil erosion to support people's livelihoods.

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. MATERIALS AND METHODS: This was a cross-sectional multicenter study conducted at Allahabad (Uttar Pradesh), Bengaluru (Karnataka), Chennai (Tamil Nadu), Kolkata (West Bengal), Hyderabad (Telangana), Nasik (Maharashtra), Rohtak (Haryana), Pune (Maharashtra), New Delhi (Delhi), Srinagar (Kashmir), and Vizag (Andhra Pradesh) enrolling 2599 pregnant women. Estimation of thyroid stimulating hormone (TSH), free T4, and antithyroid peroxidase (TPO) antibodies was carried out using Roche modular kit using ECLIA technology in a central laboratory. RESULTS: We found in our study population that 13.13% of pregnant women have hypothyroidism (n = 388), using a cutoff TSH level of 4.5 µIU/ml. This prevalence was much higher using the American Thyroid Association criteria. Anti-TPO antibodies were positive in 20.74% of all pregnant women (n = 613), whereas 40% (n = 155) of hypothyroid pregnant women were positive for anti-TPO antibodies. CONCLUSION: This study concludes that there is a high prevalence of hypothyroidism (13.13%), majority being subclinical in pregnant women during the first trimester from India and universal screening of hypothyroidism may be desirable in our country.

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.