In this study we present a systematic and detailed morphological characterization of tephra particles from different eruptions (Fontana Lapilli, Masaya, Nicaragua; Keanakāko'i Formation, Kilauea, ...USA; recent dome explosions of Soufriere Hills volcano, Montserrat) and the calculation of their Terminal Fall Velocity (TFV) as obtained based on different drag prediction models (i.e.,
Wilson and Huang, 1979; Haider and Levenspiel, 1989; Ganser, 1993; Dellino et al., 2005). In particular, particle sphericity, and, therefore, particle surface area, is essential for the calculation of TFV of irregular-shape particles but is of complex determination. Various attempts have been proposed. According to our results, 2D morphological characterization of volcanic particles is a fast and simple application for a wide range of particle size and provides consistent sphericity and settling-velocity values. 3D scanning also provides a promising tool for lapilli-sized tephra (>
2
cm). In contrast, gas-adsorption-derived surface area is not suitable for the calculation of TFV of volcanic particles mostly because it mainly describes the surface contribution of nanometric pores that are not expected to affect significantly TFV and because bulk-sample analysis is representative of neither individual particles nor of the whole particle population. Settling velocities calculated using values of surface area derived from gas adsorption analyses are up to two orders of magnitude lower than the values obtained through 2D analysis. In addition, our results also show how the influence of particle shape on TFV increases with particle size. In particular, calculated TFV converges at small particle sizes (≥
3 ϕ) regardless of the model applied, suggesting that the spherical assumption is appropriate for this size fraction (discrepancies with the spherical model are within 10%). Discrepancies with the spherical model increase with particle size up to about 50% and depend on the choice of both the TFV model and the morphological parameterization used.
In particular, the drag prediction model of
Ganser (1993) is sensitive to the effect of particle morphology on TFV and is well suited for all sizes and Reynolds numbers of typical tephra particles. Finally, our results show how individual size categories (whole- and half-ϕ) are not associated with individual TFV values but with a range of values, which increases with class size. Nonetheless, the half-ϕ system is associated with a smaller standard deviation than the whole-ϕ system, and is therefore more appropriate for the modeling of tephra dispersal. In any case, for dispersal modeling purposes, it is more appropriate to indicate a range of settling velocities for each size class rather than giving an average value.
► Morphologic analysis of tephra particles. ► Application of the gas adsorption method on tephra particles. ► Influence of the morphologic analysis on Terminal Fall Velocity determination. ► Evaluation of different models for terminal velocity determination.
The May, 2008, Chaitén (southern Chile) eruption was characterized by several explosive events, each associated with plumes which reached up to about 19 km above sea level on May 6. A study of the ...textural and physical features of the juvenile clasts erupted during the climactic phase of the 2008 eruption of Chaitén is presented. Pumice clasts show unimodal density distribution (main mode at 600 kg/m
3
), average vesicularity of about 69 %, a glassy groundmass with no microcrystals, and vesicles with dimension between ∼1 μm and ∼2 mm. They also show a unimodal vesicle size distribution with most frequent vesicle size in the range 0.05–0.08 mm and an estimated vesicle number density of 1.3 ± 0.5 × 10
5
mm
−3
related to a rapid nucleation event produced during the late phases of magma rise. This is confirmed by the absence of microcrystals that could otherwise have delayed vesicle formation and allowed the magma to maintain a low viscosity and a supersaturation in volatiles. Vesiculation and fragmentation were triggered by a sudden decompression of the melt associated with the opening of the volcanic conduit (∼10 MPa s
−1
).
The 2008–2013 eruption of Chaitén Volcano (Chile) was a long-lasting eruption whose climactic phase (May 6, 2008) produced a sub-Plinian plume, with height ranging between 14 and 20 km that dispersed ...to the NE, reaching the Atlantic coast of Argentina. The erupted material was mainly of lithic origin (∼77 wt%), resulting in a unimodal total grain size distribution (TGSD) dominated by coarse ash (77 wt%), with Md
ϕ
of 2.7 and σ
ϕ
of 2.4. Lapilli clasts (>2 mm) dominate the proximal deposit within ~20 km of the vent, while coarse (63 μm–2 mm) and fine ash (<63 μm) sedimented as far as 800 km from vent, generating mostly poly-modal grain size distributions across the entire deposit. Given that most of the mass is sedimented in proximal areas, results show that possible contributions of later explosive events to the thickness of the distal deposit where layers are less distinguishable (>400 km) do not significantly affect the determination of the TGSD. In contrast, gaps in data sampling in the medial deposit (in particular the gap between 50 and 350 km from vent that coincides with shifts in sedimentation regimes) have large impacts on estimates of TGSD. Particle number distribution for this deposit is characterized by a high power-law exponent (3.0) following a trend very similar to the vesicle size distribution in the juvenile pyroclasts. Although this could be taken to indicate a bubble-driven fragmentation process, we suggest that fragmentation was more likely the result of a shear-driven process because of the predominance of non-vesicular products (lithics and obsidians) and the large fraction of coarse ash in the TGSD.
On May 1st 2008 Mount Chaitén (southern Chile) interrupted a long period of quiescence, generating a sequence of explosive eruptions and causing the evacuation of Chaitén town located a few ...kilometers south of the volcano. The activity was characterized by several explosive events each associated with plumes which reached up to about 19 km above sea level. The products were dispersed across a wide area, with the finest ash reaching the Atlantic coast of Argentina. Our field observations in the proximal-medial area (3–25 km from the vent) indicate that the May 2008 tephra deposit consists of numerous layers, most of which can be correlated with individual eruptive events. These layers vary from extremely fine-grained ash to layers of lapilli and blocks, composed of both juvenile and lithic material. Here we describe the stratigraphy and physical characteristics of the May 2008 deposits, and propose a reconstruction of the timing of the May 2008 events. The deposits are mainly associated with the three main explosive phases which occurred on 1st–2nd May, 3rd–5th May and 6th May, with an estimated bulk tephra volume of 0.5–1.0 km
3
(integration of both exponential and power-law fitting). For the 6th May event, represented by a layer composed mainly of lithic lapilli and blocks (>2 mm), an isopleth map was compiled from which a 19 km plume height was determined, which is in good agreement with satellite observations.
The concerns related to particulate matter's health effects alongside the increasing demands from citizens for more participatory, timely, and diffused air quality monitoring actions have resulted in ...increasing scientific and industrial interest in low-cost particulate matter sensors (LCPMS). In the present paper, we discuss 50 LCPMS models, a number that is particularly meaningful when compared to the much smaller number of models described in other recent reviews on the same topic. After illustrating the basic definitions related to particulate matter (PM) and its measurements according to international regulations, the device's operating principle is presented, focusing on a discussion of the several characterization methodologies proposed by various research groups, both in the lab and in the field, along with their possible limitations. We present an extensive review of the LCPMS currently available on the market, their electronic characteristics, and their applications in published literature and from specific tests. Most of the reviewed LCPMS can accurately monitor PM changes in the environment and exhibit good performances with accuracy that, in some conditions, can reach
values up to 0.99. However, such results strongly depend on whether the device is calibrated or not (using a reference method) in the operative environment; if not,
values lower than 0.5 are observed.
During their lifecycle, many marine organisms rely on natural adhesives to attach to wet surfaces for movement and self-defense in aqueous tidal environments. Adhesive proteins from mussels are ...biocompatible and elicit only minimal immune responses in humans. Therefore these proteins have received increased attention for their potential applications in medicine, biomaterials, and biotechnology. The Asian green mussel Perna viridis secretes several byssal plaque proteins, molecules that help anchoring the mussel to surfaces. Among these proteins, protein-5β (Pvfp-5β) initiates interactions with the substrate, displacing interfacial water molecules before binding to the surface. Here, we established the first recombinant expression in Escherichia coli of Pvfp-5β. We characterized recombinant Pvfp-5β, finding that despite displaying a CD spectrum consistent with features of a random coil, the protein is correctly folded as indicated by MS and NMR analyses. Pvfp-5β folds as a β-sheet–rich protein as expected for an epidermal growth factor-like module. We examined the effects of Pvfp-5β on cell viability and adhesion capacity in NIH-3T3 and HeLa cell lines, revealing that Pvfp-5β has no cytotoxic effects at the protein concentrations used and provides good cell-adhesion strength on both glass and plastic plates. Our findings suggest that the adhesive properties of recombinant Pvfp-5β make it an efficient surface-coating material, potentially suitable for biomedical applications including regeneration of damaged tissues.
Abstract
Background and Aims
Combined liver-kidney transplant is the best treatment for patients with hepatic and renal failure, even though some studies reported a poor patient survival. The aim of ...our study is to summarize the clinical characteristics of subjects who undergo simultaneous combined liver-kidney transplantation (SLKT) for advanced liver and kidney disease. Furthermore, we evaluated patient and kidney survival of SLKT recipients compared to solitary kidney transplant (KT) recipients.
Method
We performed a retrospective analysis of all SLKT recipients performed in a single transplant Center (University Hospital of Modena, Italy) from 01/01/2004 to 12/31/2016. All patients were aged more than 18 years.
Results
34 SLKT were performed over 16 years of transplant activity. Mean age of recipients was 51.3 ±9.1years. Males accounted for 65% of the population. All patients were of Caucasians origin except one of African origin. Mean BMI was 69.5 ± 13.9 Kg.
Hepatitis C Virus (HCV)-related cirrhosis was the main cause (38.1%) of hepatic failure. Other causes of hepatic disease were ADPKD (26.5%), hepatitis B Virus (HBV) (11.8%), alcohol (8.8%), combined HCV-HBV infection (5.9%), Von Gierke Disease (2.9%), primary biliary cirrhosis (2.9%), and autoimmune cirrhosis (2.9%). Six patients developed hepatocellular carcinoma before undergoing SLKT.
Renal disease was caused by ADPKD (26.5%), diabetic nephropathy (14.7%), glomerulonephrites (29.4%), hepatorenal syndrome (8.8%) and other renal diseases (20.6%). Overall, 14.7% of patients was affected by Human Immunodeficiency Virus (HIV), 50% by hypertension and 41% by diabetes.
Mean MELD at transplantation was 42 (39.2-46.5) and mean serum creatinine value in pre-emptive patients was 3.09 ±1.4 mg/dl.
Mean of donors was 46.7±15.3 years and main cause of death was cranial trauma (47.1%), followed by cerebral haemorrhage (41.2%). Mean KDPI was 52% (22-63) and KDRI 1 (0.73-1.1).
Mean time on waiting list was 2.8±1.2 years and half of patients was on dialysis maintenance before SLKT. Mean ischemia time were 6.5 ±1.3 and 12.3 ±2.1 hours for liver and kidney, respectively. Only one patient (2.9%) received double kidney transplantation.
Primary induction agent was anti-IL2 receptor monoclonal antibodies (82.6%), thymoglobulin (13%) and with methylprednisolone (4.1%). Post SLKT, kidney early complication consisted of 3 delayed graft functions and 1 transplanctectomy in the only double kidney transplant recipient.
At the end of the follow-up (8±4.1 years), mean creatinine was 1.44 ± 0.5 mg/dl and kidney survival accounted for 87.9%.
Cox regression analysis showed recipient’ age as a protective factor (HR, 0.03; CI95%, 0.8-0.9) for kidney rejection and donor age as a risk factor (HR, 1.13,CI95% 1-1.1) for renal graft loss.
Patient survival at 10 years was 91.2%. Two deaths were caused by infections (50%) and 2 by digestive haemorrhages (50%).
SLKT recipients were confronted with 304 cadaveric donor KT recipients performed in the same transplant Center from 01/01/2006 to 12/31/2016. Statistical analysis showed that SLKT recipients had shorter waiting list, dialysis vintage and ischemia times. SLKT recipients had a major prevalence of diabetes and HCV infection but a lower prevalence of hypertension. DGF were less common in SLKT.
Patient and graft survival a 1, 5 and 10 years did not show statistically significant differences between SLKT and KT.
Conclusion
Our analysis shows excellent kidney and patient survival in SLKT. SLKT and KT recipients had similar 1, 5 and 10-years patient and graft survival.
Abstract
Background and Aims
The number of simultaneous liver-kidney transplants (SLKT) has been constantly increasing in the past two decades. In the US, the relative proportion of liver transplants ...performed as part of SLKT augmented from 2.7% in 2000 to 9.3% in 2016. In this rapidly evolving scenario, people living with HIV (PLWH) have been substantially excluded from SLKT. The poor prognosis of SLKT in people living with HIV (PLWH) has refrained transplant centers to perform this procedure.
Method
We retrospectively describe indications, clinical characteristics and survival of HIV-infected patients who underwent SLKT at the Transplant Centre of Modena, Italy.
Results
Since 2001 five SLKTs were performed in HIV-affected subjects. With regards to medical eligibility criteria for SLKT all the patients were on hemodialysis and had liver end-stage disease or HCC at time of transplantation (Table 1A). Mean age at transplantation was 47.8± 5.93 years and all patients were Caucasian males. Mean duration of HIV was 25 years and all patients had undetectable HIV-viral load at SLKT. The causes of end-stage renal disease were different in all recipients and only one had biopsy-proven kidney disease. Dialysis vintage was 15.8±10.2 months. Four patients had HCV-related cirrhosis and one had hepato-carcinoma (HCC).
Mean HCV-RNA at SOT was 464,327 copies/ml; in three HCV patients, the sustained virologic response to HCV therapy was obtained after transplant with peg-INF in one case (pre-direct antiviral agent era) and with a combination of sofosbuvir, daclatasvir and rifampicin in the other two. Only one patient had HBV-HDV-related cirrhosis and did not experience HBV or HDV relapse during the follow-up.
At the end of a mean follow up of 7.6±4.71 years, four out of five patients are still alive One patient died on post-transplant day 41 for disseminated candidiasis with cerebral involvement (Table1 b). During the follow-up period, HIV-VL remained undetectable over nearly 10 years. Clinical outcome was characterized by the reverse of frailty in all the patients. All of them are conducting an independent living with quality of life exceeding 90% using the EUQoL 5D-5L questionnaire. The liver function was normal and remained stable during theobservation period. Bile duct stricture and bile duct calculi were the main surgical complications.
Regarding renal function, mean serum creatinine was 1.7±0.4mg/dl corresponding to a mean estimated GFR of 47.7±5.9 ml/min. Only one patient had proteinuria (0.8 gr/daily) after 10 years of transplantation. Contrary to our expectations, no cases of graft rejections occurred during this long-term follow-up despite mean HLA mismatches of 5.75 and underexposure to the immunosuppressive agents. Withdrawn of steroids occurred after 1.8±2.5 years from SLKT. Thereafter, immunosuppressive therapy continued with monotherapy: calcineurin inhibitor in three recipients and inhibitors of the mammalian target of rapamycin in the other one.
Conclusion
Contrary to the previously published data, this case series describes a favorable clinical outcome in PLWH who received SLKT. The absence of graft rejection despite the reduced immunosuppressive therapy highlights the concept that the liver is able to induce tolerance in kidney transplantation. These results could lead other transplant programs to consider SLKT as a reliable clinical option in PLWH with liver and kidney failure.
Figure 1:
Coefficient plot of multivariable associations with graft loss in UK children and young adults. Abbreviations: eGFR – estimated glomerular filtration rate; HLA – human leucocyte antigen; CI – confidence interval
PDF
