Fluid-solid transitions in photonic crystals of soft, thermoresponsive microgels.

Microgels are often discussed as well-suited model system for soft colloids. In contrast to rigid spheres, the microgel volume and, coupled to this, the volume fraction in dispersion can be manipulated by external stimuli. This behavior is particularly interesting at high packings where phase transitions can be induced by external triggers such as temperature in the case of thermoresponsive microgels. A challenge, however, is the determination of the real volume occupied by these deformable, soft objects and consequently, to determine the boundaries of the phase transitions. Here we propose core-shell microgels with a rigid silica core and a crosslinked, thermoresponsive poly-N-isopropylacrylamide (PNIPAM) shell with a carefully chosen shell-to-core size ratio as ideal model colloids to study fluid-solid transitions that are inducible by millikelvin changes in temperature. Specifically, we identify the temperature ranges where crystallization and melting occur using absorbance spectroscopy in a range of concentrations. Slow annealing from the fluid to the crystalline state leads to photonic crystals with Bragg peaks in the visible wavelength range and very narrow linewidths. Small-angle X-ray scattering is then used to confirm the structure of the fluid phase as well as the long-range order, crystal structure and microgel volume fraction in the solid phase. Thanks to the scattering contrasts and volume ratio of the cores with respect to the shells, the scattering data do allow for form factor analysis revealing osmotic deswelling at volume fractions approaching and also exceeding the hard sphere packing limit.

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.

Osmotic pressure of suspensions comprised of charged microgels.

We determine the osmotic pressure of microgel suspensions using membrane osmometry and dialysis, for microgels with different softnesses. Our measurements reveal that the osmotic pressure of solutions of both ionic and neutral microgels is determined by the free ions that leave the microgel periphery to maximize their entropy and not by the translational degrees of freedom of the microgels themselves. Furthermore, up to a given concentration it is energetically favorable for the microgels to maintain a constant volume without appreciable deswelling. The concentration where deswelling starts weakly depends on the crosslinker concentration, which affects the microgel dimension; we explain this by considering the dependence of the osmotic pressure and the microgel bulk modulus on the particle size.

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.

Spontaneous deswelling of microgels controlled by counterion clouds.

Concentrated poly(N-isopropylacrylamide) (pNIPAM) microgel suspensions at a fixed temperature below the deswelling transition of pNIPAM exhibit spontaneous particle deswelling. The microgels deswell before they are in direct contact and in polydisperse suspensions this deswelling is most pronounced for the largest microgel particles; as a consequence, the polydispersity of the suspension is reduced. Recently, we presented a model for this spontaneous deswelling that is based on the presence of counterions originating from charged groups on the surface of the pNIPAM microgels [A. Scotti et al., Proc. Natl. Acad. Sci. USA 113, 5576 (2016)PNASA60027-842410.1073/pnas.1516011113]. Here we present numerical Poisson-Boltzmann calculations of the electrostatic potential and osmotic pressure inside and outside a pNIPAM microgel that could trigger the observed deswelling at high particle concentrations.

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.

Our Timing to Remove Peritoneal Catheter Dialysis After Kidney Transplant.

BACKGROUND: Patients on peritoneal dialysis treatment represent 15% of the global dialysis population. The major complication of peritoneal dialysis is catheter and peritoneal infection. Peritoneal dialysis patients who receive kidney transplants are at increased risk of infection because of immunosuppressive therapy. AIM: The purpose of this study is to show our ideal timing to remove peritoneal catheter after kidney transplant, which gives adequate security on renal function recovery and reduction of septic risk. METHOD OF STUDY: We analyzed the outcomes of 65 patients on peritoneal dialysis who underwent kidney transplant between 2000 and 2016. RESULTS: In 61 cases there was an immediate graft functional recovery. In 4 cases there was a delayed graft function (DGF), and we performed a hemodialysis with temporary placement of a venous catheter. In all patients we removed peritoneal dialysis catheter 30 to 45 days after transplant. There has been 1 case of catheter infection, which was treated with antibiotic therapy. DISCUSSION: Our average time to remove the peritoneal dialysis catheter was shorter than times in previous studies, between the 30th and 45th postoperative day. In the 4 cases in which there has been a DGF, we performed hemodialysis treatment to avoid, in the immediate postoperative period, direct insults to the peritoneum by local dialysis procedures. CONCLUSION: Our experience show that the 30th to 45th postoperative day is a good time frame, better yet a good watershed between the safe removal of peritoneal catheter when patients have a stabilized renal function and the possibility of leaving it in situ, to resume peritoneal dialysis in case of persistent DGF.

Assessment of climate change effects on mountain ecosystems through a cross-site analysis in the Alps and Apennines.

Mountain ecosystems are sensitive and reliable indicators of climate change. Long-term studies may be extremely useful in assessing the responses of high-elevation ecosystems to climate change and other anthropogenic drivers from a broad ecological perspective. Mountain research sites within the LTER (Long-Term Ecological Research) network are representative of various types of ecosystems and span a wide bioclimatic and elevational range. Here, we present a synthesis and a review of the main results from ecological studies in mountain ecosystems at 20 LTER sites in Italy, Switzerland and Austria covering in most cases more than two decades of observations. We analyzed a set of key climate parameters, such as temperature and snow cover duration, in relation to vascular plant species composition, plant traits, abundance patterns, pedoclimate, nutrient dynamics in soils and water, phenology and composition of freshwater biota. The overall results highlight the rapid response of mountain ecosystems to climate change, with site-specific characteristics and rates. As temperatures increased, vegetation cover in alpine and subalpine summits increased as well. Years with limited snow cover duration caused an increase in soil temperature and microbial biomass during the growing season. Effects on freshwater ecosystems were also observed, in terms of increases in solutes, decreases in nitrates and changes in plankton phenology and benthos communities. This work highlights the importance of comparing and integrating long-term ecological data collected in different ecosystems for a more comprehensive overview of the ecological effects of climate change. Nevertheless, there is a need for (i) adopting co-located monitoring site networks to improve our ability to obtain sound results from cross-site analysis, (ii) carrying out further studies, in particular short-term analyses with fine spatial and temporal resolutions to improve our understanding of responses to extreme events, and (iii) increasing comparability and standardizing protocols across networks to distinguish local patterns from global patterns.

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.

Phase behavior of binary and polydisperse suspensions of compressible microgels controlled by selective particle deswelling.

We investigate the phase behavior of suspensions of poly(N-isopropylacrylamide) (pNIPAM) microgels with either bimodal or polydisperse size distribution. We observe a shift of the fluid-crystal transition to higher concentrations depending on the polydispersity or the fraction of large particles in suspension. Crystallization is observed up to polydispersities as high as 18.5%, and up to a number fraction of large particles of 29% in bidisperse suspensions. The crystal structure is random hexagonal close-packed as in monodisperse pNIPAM microgel suspensions. We explain our experimental results by considering the effect of bound counterions. Above a critical particle concentration, these cause deswelling of the largest microgels, which are the softest, changing the size distribution of the suspension and enabling crystal formation in conditions where incompressible particles would not crystallize.

The CONTIN algorithm and its application to determine the size distribution of microgel suspensions.

We review a powerful regularization method, known as CONTIN, for obtaining the size distribution of colloidal suspensions from dynamic light scattering data. We show that together with the so-called L-curve criterion for selecting the optimal regularization parameter, the method correctly describes the average size and size distribution of microgel suspensions independently characterized using small-angle neutron scattering. In contrast, we find that when using the default regularization process, where the regularizer is selected via the "probability to reject" method, the results are not as satisfactory.

Complicated diverticulitis in kidney transplanted patients: analysis of 717 cases.

INTRODUCTION: This study aims to investigate possible risk factors for diverticulitis in kidney transplant recipients affected by colonic diverticulosis. METHODS AND RESULTS: We investigated 717 patients transplanted between 2000 and 2010. Diverticular disease was endoscopically diagnosed in 17 of 717 examined patients. Eight patients were diagnosed with autosomal dominant polycystic kidney disease (ADPKD); 9 of 17 patients underwent emergency surgery. We performed Hartmann's procedure on all patients, with a second stage performed at least 6 months later. DISCUSSION: Although the incidence of colonic diverticular perforation in kidney transplanted patients is similar to that observed in the general population, perforation in immunosuppressed patients is associated with a higher morbidity/mortality rate. In our study, the incidence of perforation is 1.25% (9 of 717), with almost half of the cases observed in patients with ADPKD (4 of 9). Such an observation is consistent with published data, in which patients with ADPKD are reported to more frequently develop colonic diverticulosis and its complications. One possible explanation might be related to a belated diagnosis of diverticulitis, which could initially simulate an inflammatory disease as a consequence of renal cysts. Also, steroids seem to be a predisposing factor for colonic perforation in these patients. CONCLUSIONS: A timely surgery can significantly reduce mortality. In cases of elective surgery, mortality and morbidity are similar to those of immunocompetent patients; accordingly, this is the goal to be pursued. Early signs and symptoms are often masked by immunosuppressive therapy. In these patients, surgeons should always perform (1) abdominal computed tomography scanning and, in the presence of diverticulitis, reduce or withdraw immunosuppressive therapy; and (2) early surgery, with Hartmann's procedure being, in our opinion, the best choice. Before transplantation, elective surgery for colonic resection should be considered in patients with ADPKD or with a history of 1 or more episodes of acute diverticulitis who then regressed with medical therapy.

Transient formation of bcc crystals in suspensions of poly(N-isopropylacrylamide)-based microgels.

We present a small-angle x-ray scattering study of crystals formed by temperature-sensitive, swollen microgel particles consisting of poly(N-isopropylacrylamide) copolymerized with acrylic acid and 5 mol % of a cross-linker. As for hard spheres, the random hexagonal close-packed structure is predominant during crystal growth and slowly transforms toward the face-centered-cubic structure. However, a transient phase of body-centered-cubic crystal is observed in an intermediate range of effective volume fractions. We estimate that the studied suspensions are close to a transition from face-centered-cubic to body-centered-cubic structure that can be understood by the tendency of the system to maximize the excluded volume and minimize the contact area between the particles.

Are postural responses to backward and forward perturbations processed by different neural circuits?

Startle pathways may contribute to rapid accomplishment of postural stability. Here we investigate the possible influence of a startling auditory stimulus (SAS) on postural responses. We formulated four specific questions: (1) can a concurrent SAS shorten the onset of automatic postural responses?; and if so (2) is this effect different for forward versus backward perturbations?; (3) does this effect depend on prior knowledge of the perturbation direction?; and (4) is this effect different for low- and high-magnitude perturbations? Balance was perturbed in 11 healthy participants by a movable platform that suddenly translated forward or backward. Each participant received 160 perturbations, 25% of which were combined with a SAS. We varied the direction and magnitude of the perturbations, as well as the prior knowledge of perturbation direction. Perturbation trials were interspersed with SAS-only trials. The SAS accelerated and strengthened postural responses with clear functional benefits (better balance control), but this was only true for responses that protected against falling backwards (i.e. in tibialis anterior and rectus femoris). These muscles also demonstrated the most common SAS-triggered responses without perturbation. Increasing the perturbation magnitude accelerated postural responses, but again with a larger acceleration for backward perturbations. We conclude that postural responses to backward and forward perturbations may be processed by different neural circuits, with influence of startle pathways on postural responses to backward perturbations. These findings give directions for future studies investigating whether deficits in startle pathways may explain the prominent backward instability seen in patients with Parkinson's disease and progressive supranuclear palsy.

Epistaxis in children under the age of two: possible marker of abuse/neglect? A retrospective study in North-Eastern Piedmont hospitals.

AIM: Epistaxis is an extremely common event at all ages; however, under two years of age epistaxis is a very rare event and recent studies carried out in Great Britain concern this event as related to possible non-accidental trauma. To date, no other studies carried out in Italy are available on this topic. METHODS: A file review of all cases of epistaxis occurred in children under the age of 2 who were admitted into the ED in our area over a period of two years was carried out. RESULTS: We have collected data concerning 10 cases of epistaxis occurred in children under 2 years of age with an incidence of 10.4 cases per 10000 accessions to the ED of children under the age of 2. Four of the cases had attendances for head injury or facial trauma. CONCLUSION: The results obtained are higher than the results of the British studies adopting the same methodology, but comparable to their surveillance data on the general population. Through the analysis of the collected data, two correlated assumptions have been made: a possible relationship between epistaxis and neglect, and a relation between epistaxis and domestic accidents.

Sinonasal inverted papilloma: 84 patients treated by endoscopy and proposal for a new classification.

AIM: To suggest a new classification system for sinonasal papilloma based on a critical analysis of surgical indications and results obtained. METHODS: We analysed surgical data from 84 cases of sinonasal papilloma treated endoscopically. RESULTS: In 58 males and 26 females, between 25 and 85 years, the ethmoid sinus (63 cases), the maxillary sinus (43), and the nasal fossa (22) were mostly involved. No case of endocranial extension or carcinoma was reported. Complications were reported in 15.4% of patients, as well as 5 recurrences (5.9%). Median follow up was 39,5 months. To categorise the tumour for the most appropriate surgical treatment, we propose a classification based on 6 main categories that depend on the location, origin and extension of the tumour. CONCLUSION: The classification that we propose presents advantages for prognosis and surgical indication in comparison with other classifications.

Tinnitus sound therapy with open ear canal hearing aids.

OBJECTIVE: The aims of this study were to evaluate the efficacy of open ear canal hearing aids in tinnitus treatment and to investigate the influence of gender, age, medication usage, tinnitus cause, tinnitus perception side, tinnitus pitch, pure tone audiometry, distortion product otoacoustic emissions, and minimal masking level on outcome. METHODOLOGY: One hundred tinnitus patients were evaluated by the tinnitus handicap inventory (THI) at the beginning of the study and after nine months of treatment. All subjects were submitted to counselling and sound enrichment from the simple sound amplification provided by the open ear canal hearing aids. RESULTS: Initial mean THI score was 54.22 (+/- 20.37) and final mean score was 28.32 (+/- 16.50), p < 0.0001. No statistically significant correlations were found between THI value reduction and the studied parameters. CONCLUSION: Open ear canal hearing aids were useful in all tinnitus patients with mild hearing loss.

A primary squamous cell carcinoma of the trachea: case report and review of the literature.

Primary windpipe tumour is extremely rare. Squamous cell carcinoma is the most common malignant form, especially in smokers. The radiological appearance of these neoplasms can be classified as intra-luminal, wall-thickening, exophytic form; the majority of the lesions are obstructive in nature and then tend to extra-luminal invasion. This tumour is usually diagnosed late on account of delayed specific symptoms: haemoptysis, dyspnoea, coughing, hoarseness, stridor. Surgery, followed by adjuvant radiotherapy, is the treatment of choice; primary radiotherapy, in inoperable cases, can represent a curative management option. A case of primary tracheal cancer is described and a review of the literature is presented.

Reassembling a system from the sensor to cerebral representation: the olfactory system in vitro.

An odorant's code is represented by activity in a dispersed ensemble of olfactory sensory neurons in the nose, activation of a specific combination of groups of mitral cells in the olfactory bulb and is considered to be mapped at divergent locations in the olfactory cortex. We present here an in vitro model of the mammalian olfactory system developed to gain easy access to all stations of the olfactory pathway. Mouse olfactory epithelial explants are cocultured with a brain slice that includes the olfactory bulb and olfactory cortex areas and maintains the central olfactory pathway intact and functional. Organotypicity of bulb and cortex is preserved and mitral cell axons can be traced to their target areas. Calcium imaging shows propagation of mitral cell activity to the piriform cortex. Long term coculturing with postnatal olfactory epithelial explants restores the peripheral olfactory pathway. Olfactory receptor neurons renew and progressively acquire a mature phenotype. Axons of olfactory receptor neurons grow out of the explant and rewire into the olfactory bulb. The extent of reinnervation exhibits features of a postlesion recovery. Functional imaging confirms the recovery of part of the peripheral olfactory pathway and shows that activity elicited in olfactory receptor neurons or the olfactory nerves is synaptically propagated into olfactory cortex areas. This model is the first attempt to reassemble a sensory system in culture, from the peripheral sensor to the site of cortical representation. It will increase our knowledge on how neuronal circuits in the central olfactory areas integrate sensory input and counterbalance damage.

In situ elongation patch in right kidney transplantation.

BACKGROUND: A short right renal vein complicates transplantation causing traction and difficulties during anastomosis. When we perform a kidney transplantation from a cadaveric donor, this problem may be resolved by using the vena cava to create a venous duct. This elongation technique is proposed to be performed during bench surgery. We propose a small change in the technique: execution of an "elongation patch" during harvesting and under cold perfusion. MATERIALS AND METHODS: From January 2004 to June 2006, we performed 12 in situ (during the harvesting procedure) vena cava elongation patches. In these cases, the right renal vein was too short. The elongation patch was used in only 8 transplantations. In the other 4 cases we sacrificed the patch to perform a direct venous anastomosis due to favorable recipient anatomical characteristics. RESULTS: The 8 transplantations performed with the elongation patch did not show vascular complications and the venous anastomosis was easy to perform. CONCLUSIONS: The "extension patch" was not associated with a greater incidence of vascular complications. Using the elongation patch during the harvest showed some advantages: performed during cold perfusion with a reduction in bench ischemia; the anatomical relationships are preserved so we can perform a calibrated suture; the perfusion of the organ allows us to observe the integrity of the anastomosis. This technique did not significantly increase the harvesting time.