Absence of crystals in the phase behavior of hollow microgels.

Solutions of microgels have been widely used as model systems to gain insight into atomic condensed matter and complex fluids. We explore the thermodynamic phase behavior of hollow microgels, which are distinguished from conventional colloids by a central cavity. Small-angle neutron and x-ray scattering are used to probe hollow microgels in crowded environments. These measurements reveal an interplay among deswelling, interpenetration, and faceting and an unusual absence of crystals. Monte Carlo simulations of model systems confirm that, due to the cavity, solutions of hollow microgels more readily form a supercooled liquid than for microgels with a cross-linked core.

Phase behavior of ultrasoft spheres show stable bcc lattices.

The phase behavior of supersoft spheres is explored using solutions of ultralow cross-linked poly(N-isopropylacrylamide)-based microgels as a model system. For these microgels, the effects of the electric charges on their surfaces can be neglected and therefore only the role of softness on the phase behavior is investigated. The samples show a liquid-to-crystal transition at higher volume fraction with respect to both hard spheres and stiffer microgels. Furthermore, stable body centered cubic (bcc) crystals are observed in addition to the expected face centered cubic (fcc) crystals. Small-angle x-ray and neutron scattering with contrast variation allow the characterization of both the microgel-to-microgel distance and the architecture of single microgels in crowded solutions. The measurements reveal that the stable bcc crystals depend on the interplay between the collapse and the interpenetration of the external shell of the ultralow cross-linked microgels.

Exploring the colloid-to-polymer transition for ultra-low crosslinked microgels from three to two dimensions.

Microgels are solvent-swollen nano- and microparticles that show prevalent colloidal-like behavior despite their polymeric nature. Here we study ultra-low crosslinked poly(N-isopropylacrylamide) microgels (ULC), which can behave like colloids or flexible polymers depending on dimensionality, compression or other external stimuli. Small-angle neutron scattering shows that the structure of the ULC microgels in bulk aqueous solution is characterized by a density profile that decays smoothly from the center to a fuzzy surface. Their phase behavior and rheological properties are those of soft colloids. However, when these microgels are confined at an oil-water interface, their behavior resembles that of flexible macromolecules. Once monolayers of ultra-low crosslinked microgels are compressed, deposited on solid substrate and studied with atomic-force microscopy, a concentration-dependent topography is observed. Depending on the compression, these microgels can behave as flexible polymers, covering the substrate with a uniform film, or as colloidal microgels leading to a monolayer of particles.

Hollow microgels squeezed in overcrowded environments.

We study how a cavity changes the response of hollow microgels with respect to regular ones in overcrowded environments. The structural changes of hollow poly(N-isopropylacrylamide) microgels embedded within a matrix of regular ones are probed by small-angle neutron scattering with contrast variation. The form factors of the microgels at increasing compressions are directly measured. The decrease of the cavity size with increasing concentration shows that the hollow microgels have an alternative way with respect to regular cross-linked ones to respond to the squeezing due to their neighbors. The structural changes under compression are supported by the radial density profiles obtained with computer simulations. The presence of the cavity offers to the polymer network the possibility to expand toward the center of the microgels in response to the overcrowded environment. Furthermore, upon increasing compression, a two step transition occurs: First the microgels are compressed but the internal structure is unchanged; then, further compression causes the fuzzy shell to collapse completely and reduce the size of the cavity. Computer simulations also allow studying higher compression degrees than in the experiments leading to the microgel's faceting.

Metachronous contralateral Leydig-cell tumour in an 8-year-old boy.

Leydig-cell tumours of the testis are rare and usually benign in children. The possibility of metachronous bilateral tumours should be considered not only for testicular teratomas but also in the follow up of a Leydig-cell tumour. Testis-sparing surgery is feasible and safe in prepubertal boys after exclusion of a malignant tumour.

Use of preputial skin as cutaneous graft after nevus excision.

We report a four-year-old boy with a nevus covering all the plantar side of his second finger on the left foot. He was also affected by congenital phimosis. Surgical excision of the nevus was indicated, but the skin defect would have been too large to be directly closed. The foreskin was taken as a full-thickness skin graft to cover the cutaneous defect of the finger. The graft intake was favourable and provided a functional repair with good aesthetic characteristic.

Lymphatic preservation using methylene blue dye during varicocele surgery: a single-center retrospective study.

OBJECTIVE: Hydrocele and testicular edema caused by division of lymphatic vessels during varicocelectomy could lead to decrease in testicular function. In-vivo methylene blue mapping of testicular lymphatic vessels should prevent damage to the lymphatic system. MATERIALS AND METHODS: We retrospectively compared outcomes for 46 patients who received an intraparenchymal injection of 0.25 ml of vital dye (isosulphan blue) before a laparoscopic or an inguinal/subinguinal spermatic vein ligation with 93 controls in whom no mapping technique was adopted. RESULTS: Methylene blue mapping of testicular lymphatics reduced the incidence of postvaricocelectomy hydrocele from 6.4% (6/93) to 2.1% (1/46); the incidence of hydrocele was 0% in all cases of successful lymphatic mapping. CONCLUSION: Mapping of testicular lymphatic drainage with intraparenchymal vital dye is an easy, safe, rapid and cost-free technique. We stress the importance of sparing the lymphatic system to ensure the best andrological outcome.