This article explores the organization and interactions of Disperse Orange 3 (DO3) hydrophobic dye molecules within hybrid organic-inorganic imogolite nanotubes. In pure water, the DO3 dye molecules ...self assemble into large insoluble 2D nanosheets whose structure is also explored by molecular dynamics simulations. The dye molecules are however efficiently solubilized in the presence of hybrid imogolite nanotubes. The filling of the internal hydrophobic cavity of the nanotubes is quantified. The organization of the molecules inside the nanotube is probed using the polarization resolved second harmonic scattering (SHS) technique coupled with simulation. At the highest loading, the dyes fill the nanotube with their principal axis parallel to the nanotube walls showing a strong SHS signal due to this encapsulation.
Second harmonic scattering experiments reveal the organization of hydrophobic dyes encapsulated inside a hybrid organic-inorganic nanotube.
Plastics are nowadays essential to our daily life for a wide range of applications. In order to face the demand of polymer markets, given the depletion of fossil feedstocks from which they are still ...most commonly produced, and with the aim to develop more ecofriendly plastic materials, the need for renewable and/or recyclable polymers is huge. Polyhydroxyalkanoates (PHAs) are a class of polyesters that could meet the challenges of such a circular economy, as they currently stand as promising bio-based, degradable and recyclable alternatives to traditional non-degradable commodity polymers that are polyolefins. PHAs typically feature different side-chain substituents on the repeating units, which beside the stereochemistry along the polymer backbone and the intrinsic characteristics of the macromolecules, are key parameters that dictate and enable tuning of their thermal, mechanical, and recyclability performances. PHAs are thus a large family of versatile polymers that are currently of topical interest in light of their end-of-life options. This review discusses the chemical recycling of natural, biosynthetic and synthetic PHAs, mainly focusing on the most common examples, namely poly(3-hydroxybutyrate) (PHB), and its related copolymers. The most relevant non-biotechnological approaches, including pyrolysis-type processes, and solvolysis with especially hydrolysis and alcoholysis, whether they are catalyzed or not, are then addressed. The latest advances on the degradation, depolymerization and upcycling of PHAs, show promising outcomes for a close-carbon cycle economy with a favorable environmental impact, as exemplified from the most recent literature.
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Stereoselective ring-opening polymerization (ROP) of cyclic esters is the privileged strategy to access stereoregular polyesters that are widely applied in various domains, such as in particular the ...biomedical and packaging fields. The production of synthetic stereo-enriched polyhydroxyalkanoates (PHAs) derived from
racemic
β-lactones by ROP is still a challenge. In this context, linear, high molar mass, narrowly dispersed PHAs, namely PBPL
CH
2
O
i
Pr
, PBPL
CH
2
O
t
Bu
and PBPL
CH
2
OTBDMS
(
M
n,SEC
up to 94 300 g mol
−1
;
M
= 1.06-1.18; TBDMS = Si
t
BuMe
2
), with syndiotactic enrichment (
P
r
= 0.76-0.87) were successfully synthesized by stereoselective ROP of the corresponding functional
racemic
β-propiolactones,
rac
-BPL
CH
2
O
i
Pr
,
rac
-BPL
CH
2
O
t
Bu
and
rac
-BPL
CH
2
OTBDMS
, respectively, which are promoted by diverse achiral diamino-bis(phenolate) yttrium complexes featuring various R′/R′′ substituents (Y{ONNO
R′,R′′
},
2a-d
). The influence of the steric hindrance of the BPL
FG
side-functionality, with FG = CH
2
O
i
Pr, CH
2
O
t
Bu, and CH
2
OTBDMS, on the ROP kinetics, stereoselectivity and thermal properties of the resulting PHAs, as a function of
2a-d
catalysts, was compared to that of the previously reported similar but less hindered BPL
FG
monomers, with FG = CH
2
OMe, CH
2
OAllyl, CH
2
OBn, and CH
2
OPh. Overall, this study evidenced that, for the newly prepared
rac
-BPL
CH
2
O
i
Pr
,
rac
-BPL
CH
2
O
t
Bu
and
rac
-BPL
CH
2
OTBDMS
monomers, due to steric constraints induced by the monomer alkoxy/silyloxy side-functionality, all ROPs afforded syndio-enriched polyesters, regardless of the catalyst used. Conversely, only combinations of a BPL
FG
monomer containing two sets of methylene hydrogens within the side-functionality,
i.e.
with FG = C
H
2
OC
H
2
X with X = H, CH = CH
2
and C
6
H
5
as in BPL
CH
2
OMe
, BPL
CH
2
OAllyl
, and BPL
CH
2
OBn
, with a yttrium catalyst bearing
ortho
/
para
-chloro substituents (
2a
), gave isotactic functional PHAs. With the latter three monomers, a catalyst with highly sterically crowded substituents on the ligand platform (
2a,b
) was necessary to recover syndio-enriched PBPL
CH
2
OMe,OAll,OBn
.
ROP of bulky functional β-lactones mediated by an achiral diamino-bis(phenolate) yttrium catalyst affords syndio-enriched polyhydroxyalkanoates.
This article explores the organization and interactions of Disperse Orange 3 (DO3) hydrophobic dye molecules within hybrid organic–inorganic imogolite nanotubes. In pure water, the DO3 dye molecules ...self assemble into large insoluble 2D nanosheets whose structure is also explored by molecular dynamics simulations. The dye molecules are however efficiently solubilized in the presence of hybrid imogolite nanotubes. The filling of the internal hydrophobic cavity of the nanotubes is quantified. The organization of the molecules inside the nanotube is probed using the polarization resolved second harmonic scattering (SHS) technique coupled with simulation. At the highest loading, the dyes fill the nanotube with their principal axis parallel to the nanotube walls showing a strong SHS signal due to this encapsulation.
Non-covalent interactions (NCIs) can play a major role in the stereoselective ring-opening polymerization (ROP) of racemic β-lactones mediated by achiral metal catalysts, towards the formation of the ...corresponding polyhydroxyalkanoates (PHAs) with a specific microstructure. Our longstanding endeavor to better understand the factors governing the stereoselective ROP of 4-substituted β-propiolactone monomers
rac
-BPL
FG
s (resulting in PBPL
FG
s; FG = (non)functional group), from catalyst systems based on diamino- or amino-alkoxy-bis(
ortho
,
para
-substituted)phenolate rare earth complexes associated with an exogenous alcohol as an initiator, indicated that the formation of iso-enriched polyesters requires the use of
ortho
-halogen-substituted phenolate ligands (halogen = F, Cl, and Br) along with a methylene alkoxide pending substituent (FG = -CH
2
OCH
2
R*) on the lactone. Any other ligand/β-lactone combination resulted in either syndiotactic or atactic PBPL
FG
s. We report herein the controlled ROP of 4-methylene-alkoxy-fluorinated substituted β-propiolactone,
rac
-BPL
CH
2
OCF
2
CHF
2
, catalyzed by diamino-bis(
ortho
,
para
-R,R-substituted)phenolate yttrium catalyst systems Y{ONNO
R2
}/
i
PrOH (with R = Me, Cl,
t
Bu, cumyl; namely
1a-d
/
i
PrOH, respectively). This monomer does not feature any outer methylene hydrogen in the alkoxide moiety (-CH
2
OC&cmb.b.line;F&cmb.b.line;
2
CHF
2
vs
. -CH
2
OC&cmb.b.line;H&cmb.b.line;
2
R*), thus enabling the evaluation of the role of outer CH
2
O(R*)C&cmb.b.line;
H&cmb.b.line;
2
R
NCIs in the stereocontrol. The
t
Bu catalyst
1c
showed the highest ROP activity (TOF up to 4650 h
−1
) out of the four catalyst systems investigated. The fluoroalkyl PHAs were recovered with molar mass values up to
M
n,NMR
= 106 000 g mol
−1
and narrow dispersity (
M
= 1.02-1.24). Detailed NMR and mass spectrometry characterization studies supported the formation of α-isopropoxy,ω-hydroxy telechelic PBPL
CH
2
OCF
2
CHF
2
chains. Catalysts
1c
and
1d
flanked with bulky phenolate substituents (R =
t
Bu, cumyl) and the chloro-substituted one
1b
all returned syndio-enriched PBPL
CH
2
OCF
2
CHF
2
s with
P
r
up to 0.87, as assessed by
13
C NMR spectroscopy. Only the methyl substituted catalyst
1a
gave atactic PHAs. Eventually, these findings support the hypothesis that both inner and outer methylene hydrogens within an alkoxymethylene exocyclic group on the
rac
-β-lactone monomer (C&cmb.b.line;H&cmb.b.line;
2
OC&cmb.b.line;H&cmb.b.line;
2
R*) are required, along with an
ortho
-chloro-substituted yttrium bisphenolate catalyst (Y{ONNO
Cl
2
}), to induce NCIs (
Cl
H&cmb.b.line;
2
C&cmb.b.line;-O-C&cmb.b.line;(R*)
H&cmb.b.line;
2
Cl
), ultimately resulting in unique isotactic synthetic PHAs.
Non-covalent interactions (NCIs) can guide stereoselective ring-opening polymerization (ROP) of racemic β-lactones mediated by achiral complexes, towards stereoregular polyhydroxyalkanoates (PHAs).
Ring-opening polymerization (ROP) of cyclic esters is a preferred approach for the preparation of various polyesters with controlled microstructures. In this work, the ROP of chiral seven-membered ...substituted- -caprolactones, namely 1-methyl- -caprolactone (CL
Me
) and 1-
n
-butyl- -caprolactone (CL
n
Bu
, aka -decalactone), was investigated to assess the potential stereoregularity of the resulting polylactones. The reactions mediated by yttrium complexes Y{ON(N)O
R2
} based on non-chiral diamino-bis(
o
,
p
-disubstituted-phenolate) ligands, associated with an exogeneous alcohol as a co-initiator, were effectively catalyzed - that is, with good control over molar mass values, narrow dispersity, and chain-end fidelity. However, the tacticity of the homopolymers obtained from racemic monomers
rac
-CL
Me
or
rac
-CL
n
Bu
could not be evidenced by NMR spectroscopy, as outlined in previous literature reports. Alternatively, the ring-opening copolymerization (ROCOP) of equimolar mixtures of (
R
)-CL
n
Bu
/(
S
)-CL
Me
enabled, indirectly, the assessment of the catalyst stereocontrol through the evaluation of the ultimate degree of alternation of the inserted units of each comonomer. While NMR spectroscopy again did not enable unambiguous evaluation of the copolymer topology/sequence, detailed MALDI-ToF and high-resolution ESI mass spectrometric analyses rewardingly revealed two major series of macromolecules, cyclic and linear ones. Both series of macromolecules showed randomly distributed units of both comonomers, thereby evidencing the absence of any significant stereocontrol from the yttrium catalyst over these large, seven-membered substituted -caprolactones. This latter lack of stereocontrol is assumed to arise from a too long range between adjacent chiral centers, preventing an effective chain-end stereocontrolled mechanism.
The ROCOP of equimolar mixtures of (
R
)-CL
n
Bu
/(
S
)-CL
Me
enabled the assessment of the ROP stereocontrol ability of yttrium catalysts through the degree of alternation
via
detailed mass spectrometric analyses.
Stereoselective ring-opening polymerization (ROP) of cyclic esters is the privileged strategy to access stereoregular polyesters that are widely applied in various domains, such as in particular the ...biomedical and packaging fields. The production of synthetic stereo-enriched polyhydroxyalkanoates (PHAs) derived from racemic β-lactones by ROP is still a challenge. In this context, linear, high molar mass, narrowly dispersed PHAs, namely PBPL CH 2 O i Pr , PBPL CH 2 O t Bu and PBPL CH 2 OTBDMS ( M n,SEC up to 94 300 g mol −1 ; Đ M = 1.06–1.18; TBDMS = Si t BuMe 2 ), with syndiotactic enrichment ( P r = 0.76–0.87) were successfully synthesized by stereoselective ROP of the corresponding functional racemic β-propiolactones, rac -BPL CH 2 O i Pr , rac -BPL CH 2 O t Bu and rac -BPL CH 2 OTBDMS , respectively, which are promoted by diverse achiral diamino-bis(phenolate) yttrium complexes featuring various R′/R′′ substituents (Y{ONNO R′,R′′ }, 2a–d). The influence of the steric hindrance of the BPL FG side-functionality, with FG = CH 2 O i Pr, CH 2 O t Bu, and CH 2 OTBDMS, on the ROP kinetics, stereoselectivity and thermal properties of the resulting PHAs, as a function of 2a–d catalysts, was compared to that of the previously reported similar but less hindered BPL FG monomers, with FG = CH 2 OMe, CH 2 OAllyl, CH 2 OBn, and CH 2 OPh. Overall, this study evidenced that, for the newly prepared rac -BPL CH 2 O i Pr , rac -BPL CH 2 O t Bu and rac -BPL CH 2 OTBDMS monomers, due to steric constraints induced by the monomer alkoxy/silyloxy side-functionality, all ROPs afforded syndio-enriched polyesters, regardless of the catalyst used. Conversely, only combinations of a BPL FG monomer containing two sets of methylene hydrogens within the side-functionality, i.e. with FG = C H 2 OC H 2 X with X = H, CH = CH 2 and C 6 H 5 as in BPL CH 2 OMe , BPL CH 2 OAllyl , and BPL CH 2 OBn , with a yttrium catalyst bearing ortho / para -chloro substituents (2a), gave isotactic functional PHAs. With the latter three monomers, a catalyst with highly sterically crowded substituents on the ligand platform (2a,b) was necessary to recover syndio-enriched PBPL CH 2 OMe,OAll,OBn .
Human exposure to bisphenol A (BPA) is mainly due to migration from plastic packaging into food and beverages. Studies reported BPA endocrine disruptions through interactions with different nuclear ...receptors, including the arylhydrocarbon receptor (AhR). AhR mediates xenobiotic responses and regulates expression of drug-metabolizing enzymes (DMEs), including many CYP450s. This study aimed to assess the effects of BPA maternal exposure on CYP450s expression in fetal brain. Sprague-Dawley dams were exposed to BPA concentrations of 0, 0.5, 5, and 50 mg/L in drinking water, individually, and with nicotine. Fetal brains were isolated at gestational days GD14 and GD19, and protein expression was assessed by Western blotting. Results showed a BPA-induced significant decrease in CYP1B1 expression levels at GD14 (p = 0.001), and CYP19A1 (aromatase) expression at both mid- and late-stage development (p < 0.001). In addition, nicotine individually decreased expression levels of all examined protein targets, significantly for CYP1B1 (p < 0.001), CYP19A1 (p = 0.010), AhRR (p = 0.042), and ARNT (p < 0.001), compared to control. When combined with BPA, nicotine suppressive effects were attenuated at both GD14 and GD19. In conclusion, BPA suppresses CYP1B1 and CYP19A1 expression in fetal brain, and attenuates the suppressive effects of nicotine. Observed effects may be mediated by AhR-ARNT independent mechanisms that need further examination.
•Effects of maternal exposure to BPA on protein expression, and modulation by nicotine were examined in fetal brain.•High BPA dosing significantly decreased expression levels of CYP1B1 and CYP19A1 (aromatase) at mid-developmental stage.•Nicotine decreased expression of all examined targets at both mid- and late-developmental stages compared to control.•When combined with BPA, nicotine suppressive effects were attenuated at both mid- and late-developmental stages.
In the LTE EPC, many network entities and interfaces have to be maintained and updated regularly. Moreover, to accommodate more users, new hardware must be integrated, although rarely used. To ...address these challenges, the EPC can be moved to the cloud using two modern technologies: SDN and NFV. In this paper, we study the impact of integrating these novel technologies on LTE networks. We propose a hybrid approach for selecting whether to apply NFV or SDN on each gateway at a given time while minimizing the network load taking into consideration key network parameters such as the number of active datacenters, the deployment city population, the intensity at a given time, the QoS class identifier (QCI), and the delay budget. We formulate the SDN decomposition/NFV virtualization selection as an optimization problem where the objective is to minimize the network load subject to a set of constraints. Our results show that our proposed solution is more responsive to the dynamic state of the network such that for a given gateway, at a certain time slot, an SDN decomposition might be the optimal choice; while at another time slot with a different network state, the NFV architecture might be more suitable.
Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematopoietic disorders characterized by peripheral blood cytopenias, blood cells dysplasia, and increased risk for progression to ...acute leukemia.Physicians should be vigilant in diagnosing MDS and should be aware of the contemporary therapies that are always in progress. Most of the data on MDS epidemiology and management comes from developed countries. The incidence and features of MDS in the Arab countries, among them Lebanon, are not known. We undertook a nationwide epidemiological registry study of all newly diagnosed MDS cases through 2010-2011. Patients were referred by 21 hematologists/oncologists practicing in 17 hospitals and medical centers distributed across the entire country. 58 patients (29 males and 29 females) with confirmed MDS were included. The calculated incidence rate of MDS was 0.71 per 100,000 people. The median age at diagnosis was 73 years (range 16-86). The most common complaints on presentation were fatigue (70.7%), weakness (60.3%) and pallor (43.1%). Most patients were diagnosed as refractory anemia with excess blasts (RAEB; 36.2%) and refractory cytopenia with multilineage dysplasia (RCMD; 32.8%). This paper constitutes the first epidemiological report on the incidence and specific subtypes of MDS in Lebanon.
