In snow, water coexists in solid, liquid and vapor states. The relative abundance of the three phases drives snow grain metamorphism and affects the physical properties of the snowpack. Knowledge of ...the content of the liquid phase in snow is critical to estimate the snowmelt runoff and to forecast the release of wet avalanches. Liquid water does not spread homogeneously through a snowpack because different snow layers have different permeabilities; therefore, it is important to track sudden changes in the amount of liquid water within a specific layer. We reproduced water percolation in the laboratory, and used Raman spectroscopy to detect the presence of the liquid phase in controlled snow samples. We performed experiments on both fine- and coarse-grained snow. The obtained snow spectra are well fitted by a linear combination of the spectra typical of liquid water and ice. We progressively charged snow with liquid water from dry snow up to soaked snow. As a result, we exploited continuous, qualitative monitoring of the evolution of the liquid water content as reflected by the fitting coefficient c.
The current devices used to produce massive amounts of snow (i.e., snow machines) can be improved with concern to both the energy efficiency and the quality of snow. Here we investigate an ...alternative snow production method based on the ultrasonic nebulization of water and its subsequent condensation on the cold surfaces of a refrigerator. Inspection of the snow samples with a stereo optical microscope shows both dendritic and granular snow morphologies. The characterization of the samples by Raman spectroscopy shows a behavior consistent with that of a natural, low-density snow. Our results indicate that ultrasonic nebulization of water is an effective strategy for producing natural-like snow at the laboratory scale.
With the goal of substituting a hard metallic material for the soft Ultra High Molecular Weight Polyethylene (UHMWPE) presently used to make the bases of skis for alpine skiing, we used two ...non-thermodynamic equilibrium surface treatments with ultra-short (7-8 ps) laser pulses to modify the surface of square plates (50 × 50 mm
) made of austenitic stainless steel AISI 301H. By irradiating with linearly polarized pulses, we obtained Laser Induced Periodic Surface Structures (LIPSS). By laser machining, we produced a laser engraving on the surface. Both treatments produce a surface pattern parallel to one side of the sample. For both treatments, we measured with a dedicated snow tribometer the friction coefficient µ on compacted snow at different temperatures (-10 °C; -5 °C; -3 °C) for a gliding speed range between 1 and 6.1 ms
. We compared the obtained µ values with those of untreated AISI 301H plates and of stone grinded, waxed UHMWPE plates. At the highest temperature (-3 °C), near the snow melting point, untreated AISI 301H shows the largest µ value (0.09), much higher than that of UHMWPE (0.04). Laser treatments on AISI 301H gave lower µ values approaching UHMWPE. We studied how the surface pattern disposition, with respect to the gliding direction of the sample on snow, affects the µ trend. For LIPSS with pattern, orientation perpendicular to the gliding direction on snow µ (0.05) is comparable with that of UHMWPE. We performed field tests on snow at high temperature (from -0.5 to 0 °C) using full-size skis equipped with bases made of the same materials used for the laboratory tests. We observed a moderate difference in performance between the untreated and the LIPSS treated bases; both performed worse than UHMWPE. Waxing improved the performance of all bases, especially LIPSS treated.
Surface irradiation of AISI 301 with ultra-short linearly polarized pulses between 247 fs and 7 ps resulted in laser induced periodic surface structures (LIPSS). Scanning electron microscope ...micrographs taken after the laser treatment show the formation of sub-micrometer sized arrays of nearly parallel ripples slightly differing from each other, depending on the specific treatment adopted. Static contact angle data indicate that LIPSS induce a marked hydrophobic behavior of the treated surfaces. The friction coefficient of laser treated and pristine AISI 301 surfaces gliding on compact snow was compared to that of ultra-high molecular weight polyethylene. The friction coefficients of the laser treated samples are intermediate between those of bare AISI 301 and of UHMWPE. The changes in contact angle and surface morphology of the samples after extensive tribometer tests were tested to investigate the durability of LIPSS.
The hydrogen bond network has a major role in determining the physical and chemical properties of water both in the solid and in the liquid state. In the bulk liquid phase, there is a coexistence of ...water molecules with different degrees of coordination and their relative amount changes according to the conditions (
e.g.
, temperature, presence of solutes). Ice shows a larger amount of topologically under-coordinated water molecules at the surface as compared to the bulk. Snow is composed of many ice crystallites, and it differs from bulk ice because of the much larger specific surface area. The OH-stretching band is the most intense signal of the Raman spectrum of water, and it gives direct insight about the hydrogen bond network. In this work we compared the OH-stretching region of the Raman spectra of water, ice and snow acquired with excitations in the visible (532 nm) and in the UV-C range (250-200 nm) by exploiting the tunability of the synchrotron radiation. By moving towards the highest energy excitation we observed in liquid water a monotonic increase of the relative intensities of the peaks associated with weakly hydrogen-bonded water molecules. With visible excitation, the Raman spectrum of snow displays a larger contribution from weakly hydrogen-bonded water molecules at the surfaces when compared to the spectrum of bulk ice. By using excitation sources in the UV-C range, we observe a further enhancement of the contribution of the surfaces in the spectra of snow. By considering the reported changes of the water absorption coefficient in relation to the hydrogen bonding environment, we interpreted our results as a preferential pre-resonance excitation of weakly hydrogen-bonded water molecules induced by the UV-C sources.
UV excitation selectively enhances Raman scattering from weakly hydrogen-bonded water molecules.
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•We prove the sensitivity of Raman spectroscopy to snow micro and nanostructure.•By first principles MD we model the surface vibrations of single crystal ice.•Raman spectra of fresh ...snow are insensitive to UV-A radiation.
We investigated if the Raman spectrum of snow is affected by the highly differentiated snow morphology. The latter is subjected to continuous changes driven by the variation of ambient parameters, mainly temperature and humidity as snow progresses from freshly deposited, to compact, to icy. We measured the Raman spectrum of snow grains of different size and morphology on the temperature interval between −5.5 °C and −0.5 °C approaching the melting point. We found systematic differences with respect to bulk ice Ih in the OH-stretching band of snows with different histories. We attribute the observed spectral differences to the change of the molecular arrangement of water molecules between bulk and surface sites. We investigate this characteristic via molecular dynamics DFT simulations of bulk ice and of three thin slabs cut along specific surfaces. We analysed the simulated Raman spectra and compared their distinguishing features to those of experimental spectra of snow. The Raman features of the OH-stretching band allow to distinguish among layers inside a snowpack, each layer being characterized by a different specific surface area. This is relevant to estimate the mechanical stability of the snowpack itself. The influence of UV-A irradiation on snow is discussed.
Purpose
The presence of many asymptomatic COVID-19 cases may increase the risks of disease dissemination, mainly for physicians. There are numerous reports on the frequent findings of sudden anosmia ...or hyposmia, before or at the same time of the typical COVID-19 symptoms onset. The aim of this study was to verify the association of olfactory impairment and COVID-19, providing a basis for subsequent research in the field of COVID-19 clinical heterogeneity.
Methods
We developed a 15-item online questionnaire on “Sudden Olfactory Loss (SOL) and COVID-19” that was administered during March 2020 to Italian general practitioners registered to a social media group.
Results
One hundred and eighty responses were received. SOL was identified as a significant sign of infection in COVID-19 patients, mainly aged between 30 and 40 years, even in the absence of other symptoms. SOL was present as an initial symptom in 46.7% of subjects, and in 16.7%, it was the only symptom. Among the COVID-19 confirmed cases, SOL occurred as the only symptom in 19.2% of patients.
Conclusion
SOL could represent a possible early symptom in otherwise asymptomatic COVID-19 subjects. Subjects affected by SOL should be considered as potential COVID-19 cases.
Level of evidence
4.
Renal Involvement in Churg-Strauss Syndrome Sinico, Renato Alberto; Toma, Lucafrancesco Di; Maggiore, Umberto ...
American journal of kidney diseases,
05/2006, Letnik:
47, Številka:
5
Journal Article
Recenzirano
Background:
Churg-Strauss syndrome (CSS) is a rare disorder characterized by asthma, eosinophilia, and systemic vasculitis. Renal involvement is not regarded as a prominent feature, and its ...prevalence and severity vary widely in published reports that usually refer to small series of selected patients.
Methods:
We examined the prevalence, clinicopathologic features, and prognosis of renal disease in 116 patients with CSS.
Results:
There were 48 men and 68 women with a mean age of 51.9 years (range, 18 to 86 years). Signs of renal abnormalities were present in 31 patients (26.7%). Rapidly progressive renal insufficiency was documented in 16 patients (13.8%); urinary abnormalities, 14 patients (12.1%); and chronic renal impairment, 1 patient. There were 3 additional cases of obstructive uropathy. Sixteen patients underwent renal biopsy, which showed necrotizing crescentic glomerulonephritis in 11 patients. Other diagnoses were eosinophilic interstitial nephritis, mesangial glomerulonephritis, and focal sclerosis. Antineutrophil cytoplasmic antibody (ANCA) was positive in 21 of 28 patients (75.0%) with nephropathy versus 19 of 74 patients without (25.7%;
P < 0.001). In particular, all patients with necrotizing crescentic glomerulonephritis were ANCA positive. After a median follow-up of 4.5 years, 10 patients died (5 patients with nephropathy) and 7 patients developed mild chronic renal insufficiency. Five-year mortality rates were 11.7% (95% confidence interval, 3.9 to 33.3) in patients with nephropathy and 2.7% (95% confidence interval, 0.7 to 10.7) in those without (
P = 0.10).
Conclusion:
Renal abnormalities are present in about one quarter of patients with CSS. The prevailing picture is ANCA-associated necrotizing crescentic glomerulonephritis; however, other forms of nephropathy also may occur. Outcome and long-term follow-up usually are good.
The site of reduced electrolyte transport in Bartter's syndrome (BS) was studied with a new technique whereby resorption can be separately measured as equivalent volumes of free water generated along ...the ascending limb of Henle's loop (CH2O-HL) and cortical distal tubule (CH2O-DT): the fractional proximal resorption (FPR) and the volume of free water dissipated along collecting ducts (CD) by back diffusion (CH2O-BD) in the absence of ADH are also measured during maximal water diuresis. Data are expressed as ml . min-1 GFR-1 . 100. The studies were performed on 2 brothers with all clinical and laboratory features of BS. They achieved external Na balance within 3 days when placed on either 10, 100, or 230 mEq Na daily. With the 100-mEq-Na diet indomethacin caused a stable 1.5 kg weight gain. FPR was 0.69 in normal controls (NC), 0.77 in BS; CH2O-HL 16.7 vs. 16.4; CH2O-DT 9.7 vs. 3.9; CH2O-BD 13.8 vs. 13.8; CH2O (free water excretion) 12.5 vs. 6.1; urine flow rate (V) 17.6 vs. 9.9. Thus, BS is characterized by a slight fall in proximal delivery, normal HLNa transport, a striking impairment of DTNa transport and preserved interstitial hypertonicity which drives a normal osmotic flow of CH2O-BD. Aspirin injected intravenously during water load affected CH2O and V in proportion to the change in GFR, which fell from 145 +/- 19 to 114 +/- 12 ml . min-1, p less than 0.01). Thus, the primary abnormality of BS is impaired Na transport along the early portion of the distal tubule. This is compensated by volume contraction attended by reduced proximal delivery and full activation of renin-angiotensin-aldosterone system. Consequently, more distal cation exchange sites reclaim Na+ at the expenses of excessive K+ and H+ losses, trapping NH4Cl within tubular lumen and generating hypokalemic metabolic alkalosis. The excess angiotensin is counterbalanced by increased prostaglandin (PG) secretion, which brings renal vascular resistances toward normal and causes tachyphylaxis to angiotensin. Inhibition of PG synthesis leads to a fall in GFR and proximal delivery: this causes distal delivery to fall below reabsorptive capacity for Na: therefore both Na and K retention ensues causing partial volume reexpansion till a new balance is established. PGs do not affect either Na or Cl resorption in BS except by a purely hemodynamic action.
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