Why does silicon have an indirect band gap?

It is difficult to intuit how electronic structure features-such as band gap magnitude, location of band extrema, effective masses, -arise from the underlying crystal chemistry of a material. Here we present a strategy to distill sparse and chemically-interpretable tight-binding models from density functional theory calculations, enabling us to interpret how multiple orbital interactions in a 3D crystal conspire to shape the overall band structure. Applying this process to silicon, we show that its indirect gap arises from a competition between first and second nearest-neighbor bonds-where second nearest-neighbor interactions pull the conduction band down from Γ to X in a cosine shape, but the first nearest-neighbor bonds push the band up near X, resulting in the characteristic dip of the silicon conduction band.

Orthopedic management of a patient with synovial chondromatosis.

This article reviews practice guidelines, diagnosis, and treatment for synovial chondromatosis, a rare, benign condition that involves the synovium of the joints, most commonly the knee. The condition also can affect the hip, ankle, shoulder, elbow, and temporomandibular joint.

Structural Dynamics of the Dengue Virus Non-structural 5 (NS5) Interactions with Promoter Stem Loop A (SLA).

The dengue virus (DENV) NS5 protein plays a central role in dengue viral RNA synthesis which makes it an attractive target for antiviral drug development. DENV NS5 is known to interact with the stem-loop A (SLA) promoter at the 5'-untranslated region (5'-UTR) of the viral genome as a molecular recognition signature for the initiation of negative strand synthesis at the 3' end of the viral genome. However, the conformational dynamics involved in these interactions are yet to be fully elucidated.

Novel broadly reactive monoclonal antibody protects against infection.

The incidence of infections attributed to antimicrobial-resistant (AMR) pathogens has increased exponentially over the recent decades reaching 1.27 million deaths worldwide in 2019. Without intervention, these infections are predicted to cause up to 10 million deaths a year and incur costs of up to 100 trillion US dollars globally by 2050.