Utilizing osteocyte derived factors to enhance cell viability and osteogenic matrix deposition within IPN hydrogels

Many bone defects arising due to traumatic injury, disease, or surgery are unable to regenerate, requiring intervention. More than four million graft procedures are performed each year to treat these defects making bone the second most commonly transplanted tissue worldwide. However, these types of graft suffer from a limited supply, a second surgical site, donor site morbidity, and pain. Due to the unmet clinical need for new materials to promote skeletal repair, this study aimed to produce novel biomimetic materials to enhance stem/stromal cell osteogenesis and bone repair by recapitulating aspects of the biophysical and biochemical cues found within the bone microenvironment. Utilizing a collagen type I-alginate interpenetrating polymer network we fabricated a material which mirrors the mechanical and structural properties of unmineralized bone, consisting of a porous fibrous matrix with a young's modulus of 64 kPa, both of which have been shown to enhance mesenchymal stromal/stem cell (MSC) osteogenesis. Moreover, by combining this material with biochemical paracrine factors released by statically cultured and mechanically stimulated osteocytes, we further mirrored the biochemical environment of the bone niche, enhancing stromal/stem cell viability, differentiation, and matrix deposition. Therefore, this biomimetic material represents a novel approach to promote skeletal repair

Precursors, Gauge Invariance, and Quantum Error Correction in AdS/CFT

A puzzling aspect of the AdS/CFT correspondence is that a single bulk operator can be mapped to multiple different boundary operators, or precursors. By improving upon a recent model of Mintun, Polchinski, and Rosenhaus, we demonstrate explicitly how this ambiguity arises in a simple model of the field theory. In particular, we show how gauge invariance in the boundary theory manifests as a freedom in the smearing function used in the bulk-boundary mapping, and explicitly show how this freedom can be used to localize the precursor in different spatial regions. We also show how the ambiguity can be understood in terms of quantum error correction, by appealing to the entanglement present in the CFT. The concordance of these two approaches suggests that gauge invariance and entanglement in the boundary field theory are intimately connected to the reconstruction of local operators in the dual spacetime.Comment: 25 pages, 6 figure

Sub-AdS Scale Locality in AdS3_3/CFT2_2

We investigate sub-AdS scale locality in a weakly coupled toy model of the AdS$_3$/CFT$_2$ correspondence. We find that this simple model has the correct density of states at low and high energies to be dual to Einstein gravity coupled to matter in AdS$_3$. Bulk correlation functions also have the correct behavior at leading order in the large $N$ expansion, but non-local effects emerge at order $1/N$. Our analysis leads to the conjecture that any large $N$ CFT$_2$ that is modular invariant and has the right low-energy density of states is dual to a gravitational theory with sub-AdS scale locality.Comment: 19 page

Simulating three dimensional self-assembly of shape modified particles using magnetic dipolar forces

The feasibility of 3D self-assembly of milli-magnetic particles that interact via magnetic dipolar forces is investigated. Typically magnetic particles, such as isotropic spheres, self-organize in stable 2D configurations. By modifying the shape of the particles, 3D self-assembly may be enabled. The design of the particles and the experimental setup are presented. The magnetic configurations of simple particle arrangements are obtained via energy minimization in simulations. The simulations show that a 3D configuration can become energetically favourable over 2D configurations, if the shape of the particle is modified

Congenital radial head dislocation with a progressive cubitus valgus: a case report

Congenital dislocation of the radial head is rare, although it is the most common congenital anomaly of the elbow. A concomitant progressive cubitus valgus of the elbow has not previously been described in literature. We describe a case of an 8-year-old girl with an unilateral congenital radial head dislocation with a progressive cubitus valgus of 35°, caused by a prematurely closing physis of the lateral humeral condyle. This might be caused by an increased pressure on the lateral physis by the anteriorly dislocated radial head. As no complaints or limitations were present, treatment was non-operative with clinical observation, with satisfactory results after a follow-up of 18 months. A concomitant progressive cubitus valgus can be present in patients with a congenital radial head dislocation. Non-operative treatment can provide satisfactory results

Unusual cause of mechanical ileus: abdominal cocoon syndrome

A 38-year-old black male patient was admitted with diarrhea and nausea over two days and aggravating pain in the meso- and epigastium that resolved after urination. He had no surgical history and only an episode of pulmonary tuberculosis five years earlier, for which he was properly treated. Physical examination revealed a tender and distended abdomen with clangorous sounds. His temperature was 36.1°C. Routine laboratory blood analyses were normal. An abdominal ultrasound revealed diffuse distention of the small intestine. A computed tomography (CT) scan showed a conglomerate of dilated small bowel loops in the meso- and hypogastrium, suggestive for a supravesical mechanical small bowel obstruction. Peritoneal thickening was seen in the right epigastrium (Figure A, white arrow). An explorative laparoscopy revealed a whitish, thickened membrane encapsulating the small bowels as a ‘cocoon’ (Figure B). Extensive adhesiolysis released an intestinal kinking in the lower abdomen, just above the bladder. No resection was needed. Histopathology of the membrane showed fibrocollagenous tissue with mixed inflammatory infiltrate

Cannabis legalisation and testing for cannabis use in safety- and risk-sensitive environments

The legalisation of cannabis by the High Court of South Africa, which was confirmed by the Constitutional Court, imposes challenges to occupational medical practitioners acting as medical review officers in compliance testing and fit-for-service medical examinations. The lipophilic character of the psychoactive component of cannabis, delta-9-tetrahydrocannabinol (Δ9-THC), and its prolonged elimination half-life, create challenges for the ethically and scientifically correct management of the legal use of cannabis in risk-sensitive environments. Important issues to consider in testing for cannabis use are: the stance of ‘zero tolerance’; screening and confirmation cut-off concentrations; and the bio-matrices used for testing. Constitutional rights relate to privacy, freedom, autonomy, freedom of religion and the equal enjoyment of rights and privileges, which must be balanced against the health and safety of others