Spinor algebra and null solutions of the wave equation

In this paper we exploit the ideas and formalisms of twistor theory, to show how, on Minkowski space, given a null solution of the wave equation, there are precisely two null directions in $\ker df$, at least one of which is a shear-free ray congruence

Twistor theory on a finite graph

We show how the description of a shear-free ray congruence in Minkowski space as an evolving family of semi-conformal mappings can naturally be formulated on a finite graph. For this, we introduce the notion of holomorphic function on a graph. On a regular coloured graph of degree three, we recover the space-time picture. In the spirit of twistor theory, where a light ray is the more fundamental object from which space-time points should be derived, the line graph, whose points are the edges of the original graph, should be considered as the basic object. The Penrose twistor correspondence is discussed in this context

Small Bowel Obstruction Secondary to a Metamucil Bezoar: Case Report and Review of the Literature

Bezoar-induced small bowel obstruction is a rare entity. It should be highly suspected in patients with gastric hypomotility disorders, psychiatric conditions, prior abdominal or bariatric surgery, or improper intake of medication. Their diagnosis is quite challenging and surgical exploration remains the best treatment of choice to ensure the viability of the small bowel tissue and relieve the obstruction. This is a case of a 48-year-old female with no previous abdominal surgery who presented with acute abdominal pain. The patient’s history was remarkable for the daily ingestion of 1.5 teaspoons of Metamucil with minimal amount of water. Computed tomography scan demonstrated dilated small bowel loops and a transition zone at the level of the mid jejunum. On laparoscopy, the patient was found to have a hard mass in the mid jejunum amenable to gentle fragmentation and breakdown. Metamucil bezoars are due to the solidification of psyllium-based substances in the gastrointestinal tract. The usual management of small bowel obstruction induced by a bezoar is exploratory laparotomy with enterotomy and primary anastomosis. Laparoscopic intervention has gained popularity among surgeons with good outcome and lower morbidity. In this unusual case, the small bowel obstruction induced by the Metamucil bezoar was safely treated with laparoscopic fragmentation alone