The "developmental hourglass'' describes a pattern of increasing morphological divergence towards earlier and later embryonic development, separated by a period of significant conservation across distant species (the "phylotypic stage''). Recent studies have found evidence in support of the hourglass effect at the genomic level. For instance, the phylotypic stage expresses the oldest and most c...

During their biosynthesis, many proteins pass through the membrane via a hydrophilic channel formed by the heterotrimeric Sec61/SecY complex. Whether this channel forms at the interface of multiple copies of Sec61/SecY or is intrinsic to a monomeric complex, as suggested by the recently solved X-ray structure of the Methanococcus jannaschii SecY complex, is a matter of contention. By introducin...

Many hierarchically modular systems are structured in a way that resembles an hourglass. This “hourglass effect” means that the system generates many outputs from many inputs through a relatively small number of intermediate modules that are critical for the operation of the entire system, referred to as the waist of the hourglass. We investigate the hourglass effect in general, not necessarily...

We present new, seeing-limited Imaging Fabry-Perot spectroscopic observations in the [OIII]5007Å line in the Hourglass region of the Lagoon nebula. As many as 900 line profiles were obtained in a region of 1′×1′ surrounding the Hourglass, each one representing a spatial element of 2′′×2′′. We find expansion of the HII region and high velocities upto −35 km s−1, which indicate Champagne flow. Ou...

Thomassen conjectured [8] that every 4-connected line graph is hamiltonian. An hourglass is a graph isomorphic to K5−E(C), where C is a cycle of length 4 in K5. In [2], it is shown that every 4-connected line graph without an induced subgraph isomorphic to the hourglass is hamiltonian connected. In this note, we prove that every 3-connected, essentially 4-connected hourglass-free line graph is ...

Existing laparoscopic box trainers consist only of static tasks and do not adequately prepare surgeons to navigate the dynamic surgical environment. This paper describes an innovative design using controlled motorized target movements to enhance the training of dynamic motor skills. The prototype was tested using 15 subjects with different surgical experience levels. The task required accurate ...

Thomassen conjectured [8] that every 4-connected line graph is hamiltonian. An hourglass is a graph isomorphic to K5−E(C4), where C4 is a cycle of length 4 in K5. In [2], it is shown that every 4-connected line graph without an induced subgraph isomorphic to the hourglass is hamiltonian connected. In this note, we prove that every 3-connected, essentially 4-connected hourglass free line graph i...

A graph G has the hourglass property if every induced hourglass S (a tree with a degree sequence 22224) contains two non-adjacent vertices which have a common neighbor in G − V (S). For an integer k ≥ 4, a graph G has the single k-cycle property if every edge of G, which does not lie in a triangle, lies in a cycle C of order at most k such that C has at least |V (C)| 2 edges which do not lie in...

Water transport through aquaporin water channels occurs extensively in cell membranes. Hourglass-shaped (biconical) pores resemble the geometry of these aquaporin channels and therefore attract much research attention. We assumed that hourglass-shaped nanopores are capable of high water permeation like biological aquaporins. In order to prove the assumption, we investigated nanoscale water tran...

INTRODUCTION Suprapubic cystostomy is performed in spinal cord injury patients in order to prevent complications associated with long-term urethral catheter drainage. We report a patient in whom suprapubic catheter did not drain urine satisfactorily and imaging studies revealed hourglass bladder. CASE PRESENTATION A female patient sustained paraplegia in a traffic accident in 1994 at the age ...