No abstract

No abstract

Mechanisms of the overlapping of gaps due to a refractive index difference minimum and Anderson localization for photonic band gap (PBG) have been used and they give a refractive index contrast difference of less than two percent for X-, L-, and W-points of the Brillouin zone for the pseudogap. Another physical process for the existence of PBG is the use of scattering strength (ε r ≥ 1) for fcc lattice structure. We have found refractive index contrast in the range 2.41–14.21 for the existence of the complete photonic band gap for bound photons (ε r ≥ 1). The lowest limit to yield a gap is 2.41 for valence photons (ε r = 1) at volume filling fraction 85.5% for spherical air atoms and at 14.5% for dielectric spheres. This work is reported for the first time and it is useful for maintaining connectivity and for easier fabrication of photonic crystals.

We have theoretically studied the occurrence of photonic band gap. Calculated values of relative width and lattice size for nematic liquid crystal ZLI-1132 and smectic ferroelectric liquid crystal (R)-4 -(1-methoxycarbonyl-ethoxy)-phenyl-4-[4-(noctyloxy)phenyl]benzoate (1MC1EPOPB) synthetic opal (SiO 2 ) infiltrated with liquid crystal as a function of temperature using a model of strong localization for the occurrence of pseudogap are reported for the W-point in the Brillouin zone. A new expression for refractive index calculation for synthetic opal infiltrated with liquid crystal is proposed. Central wavelength is also calculated and compared with the observed ones. The structure parameter and opal size are also given. This work is important for temperature tuning and anisotropy of photonic crystal.

No abstract

No abstract

No abstract

β-lactam antibiotics treat bacterial infections very effectively, but overuse and misuse have led to resistance. β-lactamase enzymes hydrolyze β-lactam antibiotics and are the primary cause of resistance in bacteria. Bacteria evolve and clinically mutate to produce such β-lactamase enzymes, which could hydrolyze newly discovered antibiotics. Therefore, carbapenems are considered to be the last resort of antimicrobial treatment. Further, different inhibitors have been discovered to fight these evolving and mutating β-lactamase enzymes resistance. These inhibitors are given in combination with the β-lactam antibiotics to treat bacterial infections effectively. But in due course of time, it has been observed that bacteria develop resistance against this combination. This is an extensive review, which discusses different classes of β-lactamase enzymes, their mechanism of action, and the role of critical structural elements like loops and catalytically relevant mutations. Such mutations and structural modifications result in expanding the spectrum of activity, making these β-lactamase enzymes resistant to the newly discovered β-lactam antibiotics and their inhibitors. Detailed knowledge of such mutations, catalytically relevant structural modifications, related kinetics, and action mechanisms could help develop new inhibitors effectively. Further, a detailed discussion of available inhibitors against each class of β-lactamase enzymes is also present.