Thomas L. Dent

Therapeutic and diagnostic colonoscopy in nonobstructive colonic dilatation

Cecal perforation has been well established as a consequence of mechanical obstruction of the distal colon and has been estimated to occur in 1.5% to 7% of patients with colon obstruction. Perforation of the cecum also occurs in cases of nonobstructive colonic dilatation (NCD). Although the incidence is unknown, the mortality rate is nearly 50%. Over an eight-year period, 44 patients (mean age 59 years) underwent 52 colonoscopic examinations for presumed NCD. Twelve patients (27%) developed NCD while convalescing from a recent operation and 29 patients (66%) had major systemic disorders that preceded the development of NCD. Medical treatment for an average of 2.6 days was uniformly unsuccessful. Mean cecal diameter prior to colonoscopy was 12.8 cm (range 9.5 to 17 cm). Based on radiographic or clinical criteria, 38 patients (86%) were successfully decompressed on the initial colonoscopic examination; mean cecal diameter decreased to 8.7 cm (p less than 0.01). Perforation of the cecum during colonsocopy occurred in one patient (2%) who survived. Fourteen patients died; six deaths were attributed solely to the patients who underwent operation. In summary, colonoscopy is a safe and effective therapeutic and diagnostic tool in cases of massive cecal dilatation. It should be considered before cecostomy in patients without radiographic evidence of pneumoperitoneum or clinical signs of peritoneal irritation.

Time-varying coupling strengths, nuclear forces and unification

Abstract We investigate the dependence of the nucleon–nucleon force in the deuteron system on the values of coupling strengths at high energy, which will in general depend on the geometry of extra dimensions. The stability of deuterium at all times after nucleosynthesis sets a bound on the time variation of the ratio of the QCD confinement scale to light quark masses. We find the relation between this ratio, which is exponentially sensitive to high-energy couplings, and fundamental parameters, in various classes of unified theory. Model-dependent effects in the Higgs and fermion mass sector may dominate even over the strong dependence of the QCD scale Λ . The binding energy of the deuteron also has an important effect on nucleosynthesis: we estimate the resulting bounds on variation of couplings.

Long-term patency of vein grafts preserved in liquid nitrogen in dimethyl sulfoxide.

Autogenous canine jugular veins were stored in 15% dimethyl sulfoxide (DMSO) in liquid nitrogen vapor for one to 28 days and then implanted in the carotid artery as autografts. The patency rate at one year was 62.5–87.5%. The patency rate of fresh jugular vein autografts placed in the carotid artery for one year was 75%. Similar autografts stored in liquid nitrogen vapor for one to 28 days without the cryopreservative DMSO exhibited a zero to 12.5% patency rate at one year. Scanning electron microscope studies revealed preservation of the endothelium in DMSO protected veins and a damaged or sloughed endothelium in veins frozen without DMSO cryopreservation.

Primordial nucleosynthesis as a probe of fundamental physics parameters

We analyze the effect of variation of fundamental couplings and mass scales on primordial nucleosynthesis in a systematic way. The first step establishes the response of primordial element abundances to the variation of a large number of nuclear physics parameters, including nuclear binding energies. We find a strong influence of the n-p mass difference (for the {sup 4}He abundance), of the nucleon mass (for deuterium), and of A=3, 4, 7 binding energies (for {sup 3}He, {sup 6}Li, and {sup 7}Li). A second step relates the nuclear parameters to the parameters of the standard model of particle physics. The deuterium, and, above all, {sup 7}Li abundances depend strongly on the average light quark mass m-circumflex{identical_to}(m{sub u}+m{sub d})/2. We calculate the behavior of abundances when variations of fundamental parameters obey relations arising from grand unification. We also discuss the possibility of a substantial shift in the lithium abundance while the deuterium and {sup 4}He abundances are only weakly affected.

Viable vein graft preservation

Homologous vein grafts are becoming increasingly useful in patients without suitable autologous saphenous veins for peripheral arterial bypass procedures [4, 81. However, fresh veins are the only tissue that has been used successfully in homograft vascular reconstruction in terms of long-term patency [4]. The advantages of a reliable method of long-term storage of viable vein segments and the ultimate creation of a vein “bank” are therefore apparent. Dimethylsulfoxide (DMSO) is a low molecular weight compound that diffuses readily across cell membranes [2] and has been shown to be an effective cryoprotectant avoiding cellular dehydration, a major cause of cell death during freezing [2]. The DMSO has been used for successful cryopreservation of other tissues [3, 61, but has not been utilized for vein graft preservation. This study assesses a method for the longterm preservation of viable vein segments by freezing in liquid nitrogen with DMSO cryopreservation.

Flexible Fiberoscopy of Urinary Conduits

During the last 2 years 7 patients with intestinal urinary conduits, exhibiting symptoms of gross hematuria and ureteral stricture or other difficulty with the conduit, were examined with flexible fiberoptic endoscopes. The entire lumen of the intestinal conduit, all urinary-intestinal anastomoses and the bladder of 1 patient were visualized successfully. Retrograde pyelography was performed on 2 patients. In 4 of 7 patients we were able to demonstrate abnormalities that were not demonstrable by any other method.

CP violation and modular symmetries

We reconsider the origin of

Treatment alternatives in renal failure and renal transplantation patients with nonobstructive colonic dilatation

mathrm{CP}

Endoscopic identification and removal of an unusual symptomatic colonic foreign body.

violation in fundamental theory. Existing string models of spontaneous

Standard Model Baryogenesis through Four-fermion Operators in Braneworlds

mathrm{CP}