1,722 research outputs found
About the limits of microfiltration for the purification of wastewaters
In the past, microfiltration was widely used as a
pretreatment step for wastewater stream purification
purposes. Experiences performed during the last years
shows that microfiltration fails to maintain its
performances for longer period of times. Many case studies
demonstrate that the adoption of microfiltration leads to
the failure of the overall process; the severe fouling of the
microfiltration membranes leads to high operating costs
with the consequence to make the treatment of the
wastewater economically unfeasible. The boundary flux
concept is a profitable tool to analyze fouling issues in
membrane processes. The boundary flux value separates an
operating region characterized by reversible fouling
formation from irreversible one. Boundary flux values are
not content, but function of time, as calculated by the subboundary
fouling rate value. The knowledge of both
parameters may fully describe the membrane performances
in sub-boundary operating regimes. Many times, for
wastewater purification purposes, ultrafiltration
membranes appear to be suits better to the needs, even they
exhibit lower permeate fluxes compared to microfiltration.
Key to this choice is that ultrafiltration appears to resist
better to fouling issues, with a limited reduction of the
performances as a function of time. In other words, it
appears that ultrafiltration exhibit higher boundary flux
values and lower sub-boundary fouling rates. In this work,
after a brief introduction to the boundary flux concept, for
many different wastewater streams (more than 20,
produced by the most relevant industries in food,
agriculture, manufacture, pharmaceutics), the boundary
flux and sub-boundary fouling rate values of different
microfiltration and ultrafiltration membranes will be
discussed and compared. The possibility to successfully
use microfiltration as a pretreatment step strongly depends
on the feedstock characteristics and, in detail, on the
particle size of the suspended matter. In most cases,
microfiltration demonstrates to be technically unsuitable
for pretreatment purposes of many wastewater streams; as
a consequence, the adoption of microfiltration pushes
operators to exceed boundary flux conditions, therefore
triggering severe fouling, that leads to economic
unfeasibility of the process in long terms
Chromium recovery by membranes for process reuse in the tannery industry
Leather tanning is a wide common industry all over the
world. In leather processing, water is one of the most
important medium, almost 40-45 L water kg-1 raw-hide or
skin is used by tanneries for processing finished leathers.
The composition of tannery wastewater presents
considerable dissimilarities in the concentration range of
pollutants both of inorganic (chlorides, with concentration
ranging from several hundred to over 10,000 mg L-1 Cl–;
sulphate (VI), ammonium ions and sulphide ions,
exhibiting concentration that ranges from tens to several
hundred mg L-1) and organic (the COD value is usually
several thousand mg L-1 O2). Throughout the years, many
conventional processes have been carried out to treat
wastewater from tannery industry: unfortunately, in this
case, biological treatment methods give rise to an
excessive production of sludge, whereas physical and
chemical methods are too expensive in terms of energy and
reagent costs. In this work, a membrane process based on
NF membrane modules was adopted to treat the tannery
feedstock after primary conventional treatment. In a first
step, the determination of all boundary flux parameters, in
order to inhibit severe fouling formation during operation,
were performed. After this, experimental work was carried
out to validate the approach. The target of water
purification was reached, that is the legal discharge to
municipal sewer system in Italy of 90% of the initial
wastewater stream volume. This allows having an
immediate cost saving of 21%. Moreover, the developed
process leads to a second benefit, that is the production of
5% of the initial volume as a highly chromium-rich
concentrate at no cost suitable to tannery process recycle
and reuse. In this case, cost saving rates exceeds 40%. At
the end, scale-up of the investigated process will be
discussed from technical and economic point of view
Structural design options for the new 34 meter beam waveguide antenna
In addition to the successful network of 34 m High Efficiency antennas recently built by JPL, the Deep Space Network (DSN) is embarking on the construction of a 34 m high performance, research and development antenna with beam waveguide optics at the Venus site. The construction of this antenna presents many engineering challenges in the area of structural, mechanical, RF, and pointing system design. A set of functional and structural design requirements is outlined to guide analysts in the final configuration selection. Five design concepts are presented covering both the conventional center-fed beam optics as well as the nonconventional, by-pass beam configuration. The merits of each concept are discussed with an emphasis on obtaining a homologous design. The preliminary results of structural optimization efforts, currently in progress, are promising, indicating the feasibility of meeting, as a minimum, all X-band (8.4 GHz) requirements, with a goal towards meeting Ka-band (32 GHz) quality performance, at the present budget constraints
Cassini: Mission to Saturn and Titan
The Cassini Mission to Saturn and Titan represents an important step into the exploration of the outerplanets. It will expand on the flyby encounters of Pioneer and Voyager and parallel the detailed exploration of the Jupiter system to be accomplished by the Galileo Mission. By continuing the study of the two giant planets and enabling detailed comparisons of their structure and behavior, Cassini will provide a tremendous insight into the formation and evolution of the solar system. In addition, by virtue of its focus on the Saturnian satellite Titan, Cassini will return detailed data on an environment whose atmospheric chemistry may resemble that of the primitive Earth. The scientific objectives can be divided into five categories: Titan, Saturn, rings, icy satellites, and magnetospheres. The key area of interest to exobiologists is Titan; the other four scientific categories will be discussed briefly to provide a comprehensive overview of the Cassini Mission
Molecular and clinical determinants of drug-induced long QT syndrome: an iatrogenic channelopathy.
More than 70 drugs present on the Swiss market can cause drug-induced long QT syndrome (LQTS), which is associated with torsades de pointes (TdP) arrhythmias, potentially leading to sudden cardiac death. Basic and clinical investigations performed during the last decade have helped a better understanding of the mechanisms and risk factors of this serious public health problem. In their vast majority, QT interval prolonging drugs block the human ERG (hERG) channel involved in the repolarisation phase of the cardiac action potential, and thus lengthen the QT interval. Beside the well-known QT interval prolonging action of class IA, IC and III anti-arrhythmic drugs, many antibiotics, neurotropic, antifungal, and antimalarial drugs are also able to cause drug-induced LQTS. Reviewing the literature indicates that the risk of QT interval prolongation and TdP is increased in females, in patients with organic heart diseases and hypokalaemia. Furthermore in a few cases, genetic factors have also been reported. However thus far, no genetic test is available to detect at-risk patients, and in consequence, drug prescribers are still relying only on the clinical history and findings to perform an evaluation of the risk. Treatment of drug-induced LQTS and TdP includes identifying and withdrawing the culprit drug(s), infusing magnesium and, in resistant cases acceleration of the heart rate. In this review article we provide a list of QT interval prolonging drugs adapted to the pharmaceuticals found on the Swiss market that can be used as a check-list for drug prescribers and at-risk patients
Nanoparticle Tracking Analysis for the Enumeration and Characterization of Mineralo-Organic Nanoparticles in Feline Urine
Urinary stone disease, particularly calcium oxalate, is common in both humans
and cats. Calcifying nanoparticles (CNP) are spherical nanocrystallite
material, and are composed of proteins (fetuin, albumin) and inorganic
minerals. CNP are suggested to play a role in a wide array of pathologic
mineralization syndromes including urolithiasis. We documented the development
of a clinically relevant protocol to assess urinary CNP in 9 healthy cats
consuming the same diet in a controlled environment using Nanoparticle
Tracking Analysis (NTA®). NTA® is a novel method that allows for
characterization of the CNP in an efficient, accurate method that can
differentiate these particles from other urinary submicron particulates. The
predominant nanoscale particles in feline urine are characteristic of CNP in
terms of their size, their ability to spontaneously form under suitable
conditions, and the presence of an outer layer that is rich in calcium and
capable of binding to hydroxyapatite binders such as alendronate and
osteopontin. The expansion of this particle population can be suppressed by
the addition of citrate to urine samples. Further, compounds targeting
exosomal surfaces do not label these particulates. As CNP have been associated
with a number of significant urologic maladies, the method described herein
may prove to be a useful adjunct in evaluating lithogenesis risk in mammals
Ultrahigh Surface Area Three-Dimensional Porous Graphitic Carbon from Conjugated Polymeric Molecular Framework
Porous graphitic carbon is essential for many applications such as energy storage devices, catalysts, and sorbents. However, current graphitic carbons are limited by low conductivity, low surface area, and ineffective pore structure. Here we report a scalable synthesis of porous graphitic carbons using a conjugated polymeric molecular framework as precursor. The multivalent cross-linker and rigid conjugated framework help to maintain micro- and mesoporous structures, while promoting graphitization during carbonization and chemical activation. The above unique design results in a class of highly graphitic carbons at temperature as low as 800 ??C with record-high surface area (4073 m2 g-1), large pore volume (2.26 cm-3), and hierarchical pore architecture. Such carbons simultaneously exhibit electrical conductivity >3 times more than activated carbons, very high electrochemical activity at high mass loading, and high stability, as demonstrated by supercapacitors and lithium-sulfur batteries with excellent performance. Moreover, the synthesis can be readily tuned to make a broad range of graphitic carbons with desired structures and compositions for many applications.clos
α1-Antitrypsin deficiency.
α1-Antitrypsin deficiency (A1ATD) is an inherited disorder caused by mutations in SERPINA1, leading to liver and lung disease. It is not a rare disorder but frequently goes underdiagnosed or misdiagnosed as asthma, chronic obstructive pulmonary disease (COPD) or cryptogenic liver disease. The most frequent disease-associated mutations include the S allele and the Z allele of SERPINA1, which lead to the accumulation of misfolded α1-antitrypsin in hepatocytes, endoplasmic reticulum stress, low circulating levels of α1-antitrypsin and liver disease. Currently, there is no cure for severe liver disease and the only management option is liver transplantation when liver failure is life-threatening. A1ATD-associated lung disease predominately occurs in adults and is caused principally by inadequate protease inhibition. Treatment of A1ATD-associated lung disease includes standard therapies that are also used for the treatment of COPD, in addition to the use of augmentation therapy (that is, infusions of human plasma-derived, purified α1-antitrypsin). New therapies that target the misfolded α1-antitrypsin or attempt to correct the underlying genetic mutation are currently under development
The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten
Several transition metals were examined to evaluate their potential for
improving the ductility of tungsten. The dislocation core structure and Peierls
stress and barrier of screw dislocations in binary
tungsten-transition metal alloys (WTM) were investigated using
first principles electronic structure calculations. The periodic quadrupole
approach was applied to model the structure of dislocation. Alloying
with transition metals was modeled using the virtual crystal approximation and
the applicability of this approach was assessed by calculating the equilibrium
lattice parameter and elastic constants of the tungsten alloys. Reasonable
agreement was obtained with experimental data and with results obtained from
the conventional supercell approach. Increasing the concentration of a
transition metal from the VIIIA group, i.e. the elements in columns headed by
Fe, Co and Ni, leads to reduction of the elastic constant and
increase of elastic anisotropy A=. Alloying W with a group
VIIIA transition metal changes the structure of the dislocation core from
symmetric to asymmetric, similar to results obtained for WRe
alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503
(2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry,
the values of the Peierls stress and barrier are reduced. The latter effect
could lead to increased ductility in a tungsten-based
alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any
of the transition metals from the VIIIA group should have similar effect as
alloying with Re.Comment: 12 pages, 8 figures, 3 table
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