235 research outputs found
Comparative Study of foF2 Measurements with IRI-2007 Model Predictions During Extended Solar Minimum
The unusually deep and extended solar minimum of cycle 2324 made it very difficult to predict the solar indices 1 or 2 years into the future. Most of the predictions were proven wrong by the actual observed indices. IRI gets its solar, magnetic, and ionospheric indices from an indices file that is updated twice a year. In recent years, due to the unusual solar minimum, predictions had to be corrected downward with every new indices update. In this paper we analyse how much the uncertainties in the predictability of solar activity indices affect the IRI outcome and how the IRI values calculated with predicted and observed indices compared to the actual measurements.Monthly median values of F2 layer critical frequency (foF2) derived from the ionosonde measurements at the mid-latitude ionospheric station Juliusruh were compared with the International Reference Ionosphere (IRI-2007) model predictions. The analysis found that IRIprovides reliable results that compare well with actual measurements, when the definite (observed and adjusted) indices of solar activityare used, while IRI values based on earlier predictions of these indices noticeably overestimated the measurements during the solar minimum.One of the principal objectives of this paper is to direct attention of IRI users to update their solar activity indices files regularly.Use of an older index file can lead to serious IRI overestimations of F-region electron density during the recent extended solar minimum
Suppression of phase transitions and glass phase signatures in mixed cation halide perovskites
Cation engineering provides a route to control the structure and properties of hybrid halide perovskites, which has resulted in the highest performance solar cells based on mixtures of Cs, methylammonium, and formamidinium. Here, we present a multi-technique experimental and theoretical study of structural phase transitions, structural phases and dipolar dynamics in the mixed methylammonium/dimethylammonium MA1-xDMAxPbBr3 hybrid perovskites (0ββ€βxββ€β1). Our results demonstrate a significant suppression of the structural phase transitions, enhanced disorder and stabilization of the cubic phase even for a small amount of dimethylammonium cations. As the dimethylammonium concentration approaches the solubility limit in MAPbBr3, we observe the disappearance of the structural phase transitions and indications of a glassy dipolar phase. We also reveal a significant tunability of the dielectric permittivity upon mixing of the molecular cations that arises from frustrated electric dipoles
High Throughput Discovery of Lightweight Corrosion-Resistant Compositionally Complex Alloys
Compositionally complex alloys hold the promise of simultaneously attaining
superior combinations of properties such as corrosion resistance,
light-weighting, and strength. Achieving this goal is a challenge due in part
to a large number of possible compositions and structures in the vast alloy
design space. High throughput methods offer a path forward, but a strong
connection between the synthesis of a given composition and structure with its
properties has not been fully realized to date. Here we present the rapid
identification of light weight highly corrosion-resistant alloys based on
combinations of Al and Cr in a Cantor-like base alloy (Al-Co-Cr-Fe-Ni).
Previously unstudied alloy stoichiometries were identified using a combination
of high throughput experimental screening coupled with key metallurgical and
electrochemical corrosion tests, identifying alloys with excellent passivation
behavior. Importantly, the electrochemical impedance modulus of the
exposure-modified, air-formed film at the corrosion potential was found as an
accurate non-destructive predictor of corrosion and passivation
characteristics. Multi-element EXAFS analyses connected more ordered type
chemical short range order in the Ni-Al 1st nn shell to poorer corrosion. This
report underscores the utility of high throughput exploration of
compositionally complex alloys for the identification and rapid screening of
vast stoichiometric space
Distribution of plantar pressure in healthy controls and patients with type 1 and 2 diabetes
WSTΔP. Celem pracy jest ocena rozkΕadu podeszwowych naciskΓ³w w grupie osΓ³b zdrowych i chorych na cukrzycΔ typu 1 i 2 przy obecnoΕci lub braku neuropatii ruchowo-czuciowej. Opisane badania stanowiΔ
wstΔp do opracowania pierwszego polskiego obuwia profilaktycznego, uwzglΔdniajΔ
cego odciΔ
ΕΌenie miejsc wysokiego ryzyka owrzodzenia na stopie.
MATERIAΕ I METODY. Przebadano grupΔ 215 zdrowych osΓ³b, 56 osΓ³b chorych na cukrzycΔ typu 1, 61 chorych na cukrzycΔ typu 2. Badano zaawansowanie przewlekΕych powikΕaΕ cukrzycy, szczegΓ³lnie neuropatii, ktΓ³rΔ
oceniano na podstawie skali NDS, NSS i przewodnictwa nerwowego. Pomiar nacisku [N/cm2] wykonano za pomocΔ
systemu Emed-SF V2.1.
WYNIKI BADAΕ. WΕrΓ³d osΓ³b zdrowych stwierdzono najwiΔksze naciski pod 2 (38,8 N/cm2) i 3 gΕowΔ
(33,4 N/cm2) koΕci ΕrΓ³dstopia. Podobne wyniki uzyskano w populacji osΓ³b chorych na cukrzycΔ typu 1. U chorych na cukrzycΔ typu 2 ciΕnienie pod 2 (45,5 N/cm2), 3 (39,6 N/cm2), 4 (31,8 N/cm2) gΕowΔ
koΕci ΕrΓ³dstopia byΕo statystycznie istotnie wyΕΌsze w porΓ³wnaniu z populacjΔ
zdrowych osΓ³b. Podobnie wysokie ciΕnienie stwierdzono pod 3 i 4 gΕowΔ
koΕci ΕrΓ³dstopia w cukrzycy typu 2 powikΕanej neuropatiΔ
.
WNIOSKI.
1. Miejscami najwiΔkszego nacisku u osΓ³b zdrowych sΔ
: paluch, piΔta, 2 i 3 gΕowa koΕci ΕrΓ³dstopia.
2. U chorych na cukrzycΔ typu 2 naciski na 2, 3, 4 i 5 gΕowie koΕci ΕrΓ³dstopia sΔ
istotnie statystycznie wiΔksze niΕΌ u osΓ³b zdrowych i chorych na cukrzycΔ typu 1.
3. U chorych na cukrzycΔ typu 2 powikΕanΔ
neuropatiΔ
ruchowΔ
i czuciowΔ
najwyΕΌsze naciski wystΔpujΔ
na 3 i 4 gΕowie koΕci ΕrΓ³dstopia i rΓ³ΕΌniΔ
siΔ one istotnie statystycznie od grupy osΓ³b zdrowych.
4. SzczegΓ³lnych zabiegΓ³w prewencyjnych w postaci odciΔ
ΕΌenia gΕΓ³wek koΕci ΕrΓ³dstopia wymagajΔ
chorzy na cukrzycΔ typu 2, zwΕaszcza powikΕanΔ
neuropatiΔ
ruchowo-czuciowΔ
.OBJECTIVE. To investigate the distribution of plantar
pressures in healthy subjects and in patients with
type 1 and 2 diabetes with or without sensorimotor
neuropathy (SMN). The paper opens a series of studies
aiming at the construction of the first Polish
prophylactic footwear, which would offload the sites
at high risk of plantar foot ulceration.
MATERIAL AND METHODS. We studied 215 healthy
subjects, 56 patients with type 1 diabetes, and 61
patients with type 2 diabetes. Chronic complications of diabetes were evaluated, especially neuropathy
based upon NDS score, NSS score and neural conduction.
We used the Emed-SF V2.1 system to measure
plantar pressures [N/cm2].
RESULTS. Among the healthy individuals the highest
pressures were observed below the second and the
third metatarsal head (38,8 N/cm2 and 33,4 N/cm2,
respectively). Similar results were found in the group
of type 1 diabetes patients. However, the patients
with type 2 diabetes mellitus had statistically significant
higher pressures below the second, the third,
and the fourth metatarsal head when compared with
non-diabetic controls (45,5 N/cm2, 39,6 N/cm2,
31,8 N/cm2, respectively). Similar results below the
third and fourth metatarsal head were observed in
the group of type 2 diabetes patients complicated
by diabetic neuropathy.
CONCLUSIONS.
1. The highest pressures in healthy subjects were
identified under great toe, the second and
third metatarsal head.
2. Patients with type 2 diabetes have significantly
higher pressures under the second through
fifth metatarsal heads as compared with
healthy subjects and type 1 diabetics.
3. In patients with type 2 diabetes complicated
by SMN the highest pressures are found under
the third and fourth metatarsal head, being significantly
different from healthy subjects.
4. Special preventive procedures i.e. offloading
metatarsal heads are necessary in patients
with type 2 diabetes, especially those with
concomitant SMN
The effect of insulin and sulodexide (Vessel Due F) on diabetic foot syndrome. Pilot study in elderly patients
Celem pracy byΕa ocena skutecznoΕci stosowania insuliny wraz z sulodeksydem (mieszanina
80% pochodnych heparyny i 20% siarczanu dermatanu) w leczeniu owrzodzeΕ stΓ³p oraz
okreΕlenie ich wpΕywu na mikrokrΔ
ΕΌenie skΓ³rne i neuropatiΔ cukrzycowΔ
. Chorzy
z zaawansowanΔ
neuropatiΔ
cukrzycowΔ
i owrzodzeniem stopy losowo przydzielono
do grupy leczonej insulinΔ
(I) z sulodeksydem (S) (n = 12) lub do grupy kontrolnej
leczonej insulinΔ
z placebo (P) (n = 6) przez 10 tygodni. Za pomocΔ
metody dopplerowskiego
lasera oceniano skΓ³rny przepΕyw krwi w stopach (LDF, laser doppler flow)
w spoczynku oraz po 30- i 60-sekundowym niedokrwieniu. Ocenie poddano rΓ³wnieΕΌ
przewodnictwo nerwowe
na podstawie czuciowych i ruchowych potencjaΕΓ³w wywoΕanych. U chorych na cukrzycΔ
skΓ³rny przepΕyw po niedokrwieniu byΕ 2,5 raza krΓ³tszy w koΕczynie z owrzodzeniem niΕΌ w stopie zdrowej. Obserwowano
znamienny wzrost przepΕywΓ³w skΓ³rnych po 30-
i 60-sekundowym niedokrwieniu po zakoΕczeniu terapii
(grupa IS, owrzodzenie stopy, LDF - 60 s; od
99,1 ± 14,3 do 218,6 ± 28,6 PU, p < 0,001, grupa
od 110,5 ± 13,0 do 164,8 ± 15,4 PU, p < 0,05). Czas
przekrwienia reaktywnego ulegΕ wydΕuΕΌeniu w grupie
IS (IS: od 30,3 ± 2,9 do 43,9 ± 2,2 s, p < 0,001; IP:
od 28,7 ± 3,0 do 33,3 ± 3,3 s, NS). W grupie IS 92%
owrzodzeΕ stΓ³p ulegΕo zagojeniu w ciΔ
gu 46,4 dnia,
natomiast w grupie IP 83% w ciΔ
gu 63,0 dnia. Badania
przewodnictwa nerwowego nie wykazaΕy rΓ³ΕΌnic
nasilenia neuropatii w obrΔbie grup i pomiΔdzy
grupami. W stopach z owrzodzeniami sulodeksyd i
insulina poprawiajΔ
przepΕyw skΓ³rny w odpowiedzi
na niedokrwienie, nie wpΕywajΔ
c na przewodnictwo
nerwowe. Kliniczne efekty dziaΕania sulodeksydu, sumujΔ
c
siΔ z dziaΕaniami insuliny, mogΔ
istotnie skracaΔ
czas niezbΔdny do caΕkowitego wyleczenia
owrzodzenia. Ostateczne potwierdzenie przedstawionych
wstΔpnych wynikΓ³w wymaga dalszych badaΕ
klinicznych.To assess the efficacy of insulin plus sulodexide
(a mixture of 80% heparin-like substances and 20%
dermatan sulphate) on diabetic ulcers, and its influence
on foot skin microcirculation and diabetic neuropathy.
Two groups of diabetic patients, suffering
from severe neuropathy and ulceration, were randomly
assigned to insulin (I) plus sulodexide (S)
(n = 12) or insulin plus placebo (P) (n = 6) therapy,
for 10 weeks. Laser Doppler assessment of foot skin
flow (LDF), at rest and 30 or 60 s after arterial occlusion,
and nerve conduction tests (sensorial evoked
and motoric conduction potentials) have been evaluated
in both groups. Postischaemic flow was 2.5
times shorter in ulcerated vs. non-ulcerated feet in
diabetic patients. A significant increase in flows after
30 and 60 s ischaemia was detected in both groups
at the end of therapy (IS group, ulcerated foot, LDF
= 60 s: from 99.1 ± 14.3 to 218.6 ± 28.6 PU, P <
0.001. IP group = from 110.5 ± 13.0 to 164.8 ± 15.4
PU, P < 0.05). The length of reactive hyperaemia was
higher in IS vs. IP group (IS: from 30.3 ± 2.9 to 43.9
± 2.2 s, P < 0.001; IP: from 28.7 ± 3.0 to 33.3 ± 3.3 s,
ns). Ninety-two percent of ulcers heals in a mean time
of 46.4 days (IS group) vs. 83% and 63.0 days, respectively,
in IP group. Nerve conduction studies have
not demonstrated within- and between-group differences.
Sulodexide and insulin improve the postischaemic
skin flow in ulcerated feet, without affecting
nerve conduction tests. The effect of sulodexide results
additive to insulin; it is clinically relevant, in the
view of the possibility of reducing the time needed
to completely heal ulcers. The ultimate validation of
these preliminary results requires extensive trials
Genetic Pathway in Acquisition and Loss of Vancomycin Resistance in a Methicillin Resistant Staphylococcus aureus (MRSA) Strain of Clonal Type USA300
An isolate of the methicillin-resistant Staphylococcus aureus (MRSA) clone USA300 with reduced susceptibility to vancomycin (SG-R) (i.e, vancomycin-intermediate S. aureus, VISA) and its susceptible βparentalβ strain (SG-S) were recovered from a patient at the end and at the beginning of an unsuccessful vancomycin therapy. The VISA phenotype was unstable in vitro generating a susceptible revertant strain (SG-rev). The availability of these 3 isogenic strains allowed us to explore genetic correlates of antibiotic resistance as it emerged in vivo. Compared to the susceptible isolate, both the VISA and revertant strains carried the same point mutations in yycH, vraG, yvqF and lspA genes and a substantial deletion within an intergenic region. The revertant strain carried a single additional frameshift mutation in vraS which is part of two component regulatory system VraSR. VISA isolate SG-R showed complex alterations in phenotype: decreased susceptibility to other antibiotics, slow autolysis, abnormal cell division and increased thickness of cell wall. There was also altered expression of 239 genes including down-regulation of major virulence determinants. All phenotypic properties and gene expression profile returned to parental levels in the revertant strain. Introduction of wild type yvqF on a multicopy plasmid into the VISA strain caused loss of resistance along with loss of all the associated phenotypic changes. Introduction of the wild type vraSR into the revertant strain caused recovery of VISA type resistance. The yvqF/vraSR operon seems to function as an on/off switch: mutation in yvqF in strain SG-R turns on the vraSR system, which leads to increase in vancomycin resistance and down-regulation of virulence determinants. Mutation in vraS in the revertant strain turns off this regulatory system accompanied by loss of resistance and normal expression of virulence genes. Down-regulation of virulence genes may provide VISA strains with a βstealthβ strategy to evade detection by the host immune system
Modified cantilever arrays improve sensitivity and reproducibility of nanomechanical sensing in living cells
Mechanical signaling involved in molecular interactions lies at the heart of materials science and biological systems, but the mechanisms involved are poorly understood. Here we use nanomechanical sensors and intact human cells to provide unique insights into the signaling pathways of connectivity networks, which deliver the ability to probe cells to produce biologically relevant, quantifiable and reproducible signals. We quantify the mechanical signals from malignant cancer cells, with 10 cells per ml in 1000-fold excess of non-neoplastic human epithelial cells. Moreover, we demonstrate that a direct link between cells and molecules creates a continuous connectivity which acts like a percolating network to propagate mechanical forces over both short and long length-scales. The findings provide mechanistic insights into how cancer cells interact with one another and with their microenvironments, enabling them to invade the surrounding tissues. Further, with this system it is possible to understand how cancer clusters are able to co-ordinate their migration through narrow blood capillaries
Evolution of Multidrug Resistance during Staphylococcus aureus Infection Involves Mutation of the Essential Two Component Regulator WalKR
Antimicrobial resistance in Staphylococcus aureus is a major public health threat, compounded by emergence of strains with resistance to vancomycin and daptomycin, both last line antimicrobials. Here we have performed high throughput DNA sequencing and comparative genomics for five clinical pairs of vancomycin-susceptible (VSSA) and vancomycin-intermediate ST239 S.Β aureus (VISA); each pair isolated before and after vancomycin treatment failure. These comparisons revealed a frequent pattern of mutation among the VISA strains within the essential walKR two-component regulatory locus involved in control of cell wall metabolism. We then conducted bi-directional allelic exchange experiments in our clinical VSSA and VISA strains and showed that single nucleotide substitutions within either walK or walR lead to co-resistance to vancomycin and daptomycin, and caused the typical cell wall thickening observed in resistant clinical isolates. Ion Torrent genome sequencing confirmed no additional regulatory mutations had been introduced into either the walR or walK VISA mutants during the allelic exchange process. However, two potential compensatory mutations were detected within putative transport genes for the walK mutant. The minimal genetic changes in either walK or walR also attenuated virulence, reduced biofilm formation, and led to consistent transcriptional changes that suggest an important role for this regulator in control of central metabolism. This study highlights the dramatic impacts of single mutations that arise during persistent S.Β aureus infections and demonstrates the role played by walKR to increase drug resistance, control metabolism and alter the virulence potential of this pathogen
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