1,286 research outputs found
Some observations on asymmetrical separation in thermal diffusion columns
Data have been obtained in steady-state batch operated thermogravitational separation columns using different binary mixtures to test the theory recently published by Morgado et al. The experimental results confirm that separations by thermal diffusion are asymmetrical except when the initial concentration is 0.5 and that the asymmetry is larger as the initial concentration deviates from 0.5 and as the separation potential increases
Nonsymmetrical separations in thermal diffusion columns
The influence of the feed composition upon the actual degrees of separation attained at the top and bottom sections of a thermogravitational column is discussed using the classical phenomenological theory of Furry, Jones, and Onsager. It is shown that, except for a feed composition of C 0 = 0.5 (mass fraction), the separation profile is nonsymmetric, i.e., the separations in the top and bottom sections of the column are nonsymmetric with respect to the feed composition, the asymmetry increasing as the feed composition moves away from C 0 = 0.5. An equation for the determination of the optimum feed location as a function of the feed composition is derived
Substratos no desenvolvimento inicial de quatro cultivares de pessegueiro e uma nectarineira.
Entre os fatores que contribuem para melhor desenvolvimento inicial das plantas, estão a qualidade da semente e o substrato utilizado.Objetivou-se avaliar o efeito do substrato na formação inicial de pessegueiro e nectarineira. O trabalho foi realizado no Departamento de Fitotecnia, da Universidade Federal de Viçosa, de fevereiro a março de 2004. Foram utilizados quatro cultivares de pessegueiro, 'Alô Doçura', 'Campinas 1', 'Relíquia' e 'Ouromel' e uma cultivar de nectarineira 'Josefina'. Sementes retiradas de frutos maturos, foram estratificadas em câmara fria, com temperatura de 5±1ºC e ausência de luz. Após a germinação, no interior da casa-de-vegetação, procedeu-se à semeadura em recipientes plásticos (3 litros), contendo os substratos: Plantmax®; Plantmax® + Areia (1:1 v/v); Plantmax® + Latossolo Vermelho (1:1 v/v); Plantmax® + Latossolo Vermelho + Areia (1:1:1 v/v). Foi utilizado o delineamento experimental inteiramente casualizado, num fatorial 5 x 4 (cultivar x substrato), com cinco repetições, considerando-se como unidade experimental cada recipiente plástico. Após 38 dias da semeadura foram analisadas: porcentagem de emergência, número de folhas, comprimento total, altura e comprimento de raiz, diâmetro do caule, massa da matéria seca total, da parte aérea e da raiz e o número de brotações primárias. O substrato teve efeito no desenvolvimento inicial de pessegueiro, obtendo-se os melhores resultados com o substrato comercial Plantmax®. O maior acúmulo de massa de matéria seca total e da parte aérea foi obtido com os cultivares 'Campinas 1' e 'Relíquia', sendo que esse último, também proporcionou maior número de brotações primárias
Diversidade genética entre progênies de maracujazeiro amarelo baseado em características morfo agronômicas.
O estudo da diversidade genética é básico para subsidiar a escolha de genitores e trabalhos de seleção e melhoramento. Este trabalho foi realizado no Departamento de Fitotecnia da Universidade Federal de Viçosa. Avaliouse a diversidade genética entre 34 famílias de meios-irmãos e 3 cultivares de maracujazeiro amarelo. O delineamento experimental foi em blocos casualizados, com 37 tratamentos, três repetições e quatro plantas por parcela. As características avaliadas foram: altura da planta e diâmetro do caule aos 60 dias após o transplantio, diâmetro do caule no início da produção, vigor, severidade de verrugose e produção por parcela. Os dados foram submetidos à análise de variância e as médias comparadas pelo método de Dunnett. Para o estudo da diversidade genética, foram estimadas as distâncias de Mahalanobis (D2) entre progênies, bem como realizadas análises de agrupamento de Tocher e das Variáveis Canônicas. Por meio da análise de variância, verificou-se efeito dos tratamentos em todas as variáveis, evidenciando a existência de variabilidade genética entre as progênies e cultivares avaliados. Houve concordância na formação dos grupos de similaridade por meio dos diferentes métodos de análise multivariada. Os grupos de tratamentos divergentes entre si e superiores foram: Grupo I - 2, 3, 6 e 15; Grupo II - 14; e Grupo III - 25
Short-Range Ising Spin Glass: Multifractal Properties
The multifractal properties of the Edwards-Anderson order parameter of the
short-range Ising spin glass model on d=3 diamond hierarchical lattices is
studied via an exact recursion procedure. The profiles of the local order
parameter are calculated and analysed within a range of temperatures close to
the critical point with four symmetric distributions of the coupling constants
(Gaussian, Bimodal, Uniform and Exponential). Unlike the pure case, the
multifractal analysis of these profiles reveals that a large spectrum of the
-H\"older exponent is required to describe the singularities of the
measure defined by the normalized local order parameter, at and below the
critical point. Minor changes in these spectra are observed for distinct
initial distributions of coupling constants, suggesting an universal spectra
behavior. For temperatures slightly above T_{c}, a dramatic change in the
function is found, signalizing the transition.Comment: 8 pages, LaTex, PostScript-figures included but also available upon
request. To be published in Physical Review E (01/March 97
Development and characterization of an injectable dextrin-based hydrogel for bone regeneration
Bone is a dynamic, highly vascularized tissue that remodels itself continuously over an individual ́s
lifetime. It
plays several important roles in
maintaining homeostasis of the body systems
[
1
,
2
]
.
However, this regenerative capac
ity is limited and,
as
in
the
case of large bone defects, where the
template for an orchestrated regeneration is absent, surgical proce
dures are needed
[
2
]
. In this respect
,
bone tissue engineering is a very challe
nging and promising field given
the need to mimic bone
mechanical and biological functions and also due to the failure of current orthoped
ic implants. The
general concept consists in the development of three
-
dimensional scaffolds, from biocompatible
materials (natu
ral or synthetic), which confer
temporary support for the regeneration of bone tissue,
while the scaffold itself will be resorbed
and replaced by new
ly formed tissue
[
2
,
3
]
.
Hydrogels are cross
-
linked networks made of natural or synthetic polymers,
which are able to
support high water contents
[
4
]
. These materials are usua
lly biocompatible, have the ability to mimic
physiological conditions, promote an environment that can protect cells or unstable drugs, their physical
characteristics can be controlled to some extent and some can be injected
in vivo
. These features make
th
em attractive materials in the biomedical field for cell encapsulation, drug or gene delivery or to act as
an interfa
ce between tissue and materials
[
4
-
7
]
. Natural polymers are advantageous for this kind of
applications since they are cheap raw materials, bear a great biocompatibility and are usually
biodegradable
[
8
]
. Dextrin is low molecular weight carbohydrate, generally regarded as safe (GRAS),
obtained from partial hydrolysis of starch or glycogen
[
9
]
. It is a glucose polymer linked by
α
-
1,4
glycosidic linkages with some degree of branching due to the presence of
α
-
1,6 bonds
[
10
]
.
I
t is
biocompatible and non
-
immunogenic, degradable by
α
-
amylases and can undergo renal clearance
avoiding tissue
accumulation
[
11
,
12
]
.
This work describes the preparation and characterization of
an injectable
dextrin
-
bas
ed
hydrogel
(oDex)
able to incorporate
nanoparticles
, cells, biomolecules or Bonelike
®
granules
[
13
]
.
Bonelike
®
is a
Biosckin
-
molecular and cell therapies S.A. proprietary synthetic bone graft, and the outcome of the
project will result in a novel injectable
presentation of
this product.
The hydrogel was produced by
dextrin oxidation with sodium periodate followed by cross
-
linking with a dihydrazide
[
14
]
. In vitro
characterization of oDex hydrogel has shown acceptable m
echanical properties, overall good
biocompatibility and the ability to be combined with other materials such as a nanogel and urinary
bladder matrix, without affecting its structure.
The cytotoxicity of the free
dihydrazide
was evaluated and
only a mild in
hibitory effect on cell proliferation was observed for the concentration used in the hydrogel
crosslinking.
The biocompatibilit
y of oDex hydrogels was confirmed
through the encapsulation of cells,
which were able to endure the gelation process.
Subcutaneou
s implants were performed in
Sasco
Sprague Dawley
rats in order to evaluate the inflammatory response and systemic effects of oDex
hydrogels and their
combination with Bonelike
®
and human mesenchymal
stem cells isolated from
umbilical cord’s Wharton jelly. After 3 and 15 days post
-
implantation, a quantitative evaluation of both
responses was performed according to ISO 10993 by a scoring system leading to a classification of the
implanted material as s
light irritant even when associated to Bonelike
®
or to the cellular system.
The
performance of oDex hydrogel combined with Bonelike granules and/or UBM in bone defects was
investigated in New Zealand rabbits. Bone defects in several anatomical locations (t
ibiae and cranium)
of non
-
critical and critical size were filled with those materials. Histological analysis showed that oDex
does not constitute a barrier for cellular colonization and proliferation since the defects that were filled
with these materials
presented a higher degree of regeneration and a higher amount of collagen fibers
with higher organization degrees, when compared with the empty defects.
Even though oDex hydrogels
purpose is to act as an injectable carrier for osteoconductive materials,
li
ke Bonelike
®
granules,
the
hydrogel itself seems to assists the regenerative pro
cess when compared with the empty defects. This
is
due to the 3D supp
ort conferred by hydrogels that
facilitates cell migration to the defect site.
Moreover, the presence of UB
M strongly stimulates the bone regeneration, for levels comparable with
the Bonelike
®
conditions, since an increase in cellular colonization and organization in the defect site
can be denoted. A sterilization protocol for oDex hydrogels by gamma and beta r
adiation was
investigated through irradiation of oxidized dextrin solutions. Despite b
oth kinds of radiation induced
slight differences in the storage modulus of the hydrogels, indicating the occurrence of chain
scission/cross
-
linking effects on the dextri
n cha
in, all
materials were gelable after the irradiation
treatments
. These effects seem to
not
be
dose or temperature dependent and
the irradiation process in
liquid or solid state also does not induce major differences in the rheology of the final hydrog
els. Due to
its known advantages, gamma radiation seems to be a suitable sterilization method for oxidized dextrin
solutions. The stability of gamma irradiated dextrin solutions was evaluated up to 8 months. Despite the
increase of storage modulus of the h
ydrogels over the time, this effect does not constitute a
disadvantage since it improves elastic behavior of the hydrogels.
oDex hydrogels provides a system
that can carry and stabilize cells, nanogels, Bonelike
®
granules and other biomolecules. It is a pr
omising
biomaterial due to its biocompatibility, and potential to promote an adequate environment for bone
regeneration. Its injectability allows
a minimal invasive surgical procedure with decreased patient
morbidity, lower risk of infection and reduced sc
ar formation.
This work has been developed in the scope of an European project that allowed collaborations with
research groups, which have complementary expertise. The tight collaboration between University of
Minho and Bioskin S.A. company, envisioning t
echnology transfer and product valorization, has resulted
in a published international patent of the product (
WO2011070529A2
)
[
15
]
. Currently, a new set of pre
-
clinical trials in sheep model
s are being planned as well as the submission of a request for the
authorization for the clinical trialsGrant SFRH/BD/64571/2009 from Fundação para a Ciência e Tecnologia
(FCT), Portugal. We thank FCT funding through EuroNanoMed ENMED/0002/2
Technology for monitoring everyday prosthesis use: a systematic review
BACKGROUND
Understanding how prostheses are used in everyday life is central to the design, provision and evaluation of
prosthetic devices and associated services. This paper reviews the scientific literature on methodologies and
technologies that have been used to assess the daily use of both upper- and lower-limb prostheses. It discusses
the types of studies that have been undertaken, the technologies used to monitor physical activity, the benefits
of monitoring daily living and the barriers to long-term monitoring.
METHODS
A systematic literature search was conducted in PubMed, Web of Science, Scopus, CINAHL and EMBASE of
studies that monitored the activity of prosthesis-users during daily-living.
RESULTS
60 lower-limb studies and 9 upper-limb studies were identified for inclusion in the review. The first studies in
the lower-limb field date from the 1990s and the number has increased steadily since the early 2000s. In contrast,
the studies in the upper-limb field have only begun to emerge over the past few years. The early lower-limb
studies focused on the development or validation of actimeters, algorithms and/or scores for activity
classification. However, most of the recent lower-limb studies used activity monitoring to compare prosthetic components. The lower-limb studies mainly used step-counts as their only measure of activity, focusing on the
amount of activity, not the type and quality of movements. In comparison, the small number of upper-limb
studies were fairly evenly spread between development of algorithms, comparison of everyday activity to
clinical scores, and comparison of different prosthesis user populations. Most upper-limb papers reported the
degree of symmetry in activity levels between the arm with the prosthesis and the intact arm.
CONCLUSIONS
Activity monitoring technology used in conjunction with clinical scores and user feedback, offers significant
insights into how prostheses are used and whether they meet the user’s requirements. However, the cost, limited
battery-life and lack of availability in many countries mean that using sensors to understand the daily use of
prostheses and the types of activity being performed has not yet become a feasible standard clinical practice.
This review provides recommendations for the research and clinical communities to advance this area for the
benefit of prosthesis users
Concerning pion parton distributions
We are grateful for constructive comments from K.-L. Cai, O. Denisov, F. de Soto, T. Frederico, J. Friedrich, C. Mezrag, V. Mokeev, W.-D. Nowak, C. Quintans, G. Salme and J. Segovia. Work supported by: National Natural Science Foundation of China (Grant nos. 12135007, 11805097); Helmholtz-Zentrum Dresden-Rossendorf High Potential Programme; Spanish Ministry of Science and Innovation (MICINN) (Grant nos. PID2020-113334GB, PID2019-107844GBC22); Generalitat Valenciana (Grant no. Prometeo/2019/087); Junta de Andalucia (Grant nos. P18-FR-5057, UHU-1264517, UHU EPIT2021); and STRONG-2020 "The strong interaction at the frontier of knowledge: fundamental research and applications" which received funding from the European Union's Horizon 2020 research and innovation programme (grant no. 824093).Analyses of the pion valence-quark distribution function (DF), u(pi) (x; sigma), which explicitly incorporate the behaviour of the pion wave function prescribed by quantum chromodynamics (QCD), predict u(pi) (x similar or equal to 1; sigma) similar to (1 - x)(beta(sigma)), beta(sigma greater than or similar to m(p)) > 2, where mp is the proton mass. Nevertheless, more than forty years after the first experiment to collect data suitable for extracting the x similar or equal to 1 behaviour of up, the empirical status remains uncertain because some methods used to fit existing data return a result for up that violates this constraint. Such disagreement entails one of the following conclusions: the analysis concerned is incomplete; not all data being considered are a true expression of qualities intrinsic to the pion; or QCD, as it is currently understood, is not the theory of strong interactions. New, precise data are necessary before a final conclusion is possible. In developing these positions, we exploit a single proposition, viz. there is an effective charge which defines an evolution scheme for parton DFs that is all-orders exact. This proposition has numerous corollaries, which can be used to test the character of any DF, whether fitted or calculated.National Natural Science Foundation of China (NSFC) 12135007
11805097Spanish Government
European Commission PID2020-113334GB
PID2019-107844GBC22Generalitat Valenciana
European CommissionGeneral Electric Prometeo/2019/087Junta de Andalucia P18-FR-5057
UHU-1264517
UHU EPIT2021STRONG-2020 "The strong interaction at the frontier of knowledge: fundamental research and applications" - European Union's Horizon 2020 research and innovation programme 824093Helmholtz-Zentrum Dresden-Rossendorf High Potential Programm
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