bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unloading‐Based Stiffness Characterisation of Cement Pastes During the Second, Third and Fourth Day After Production
Authors: Karte P. , Hlobil M. , Reihsner R. , Dörner W. , Lahayne O. , Eberhardsteiner J. , Pichler B. 
Published: March 2015

AbstractThe stiffness evolution of binder ‘cement paste’ is triggering the stiffness of concrete. In the engineering practice, concrete formworks are typically removed 24 h after production. This underlines that knowledge on mechanical properties of cementitious materials during the second, third and fourth day after production is of high relevance for the ongoing construction process. This provides the motivation to perform early‐age stiffness characterisation on hydrating cement pastes, by means of the following three test methods. Unloading modulus is determined using a novel setup for non‐destructive uniaxial compression testing including overdetermined deformation measurements. Dynamic Young's moduli are obtained from ultrasonics experiments. Isothermal differential calorimetry allows for linking the observed temporal evolution of early‐age stiffness to the hydration degree of cement. Pastes with three different compositions are investigated, defined in terms of the initial water‐to‐cement mass ratio w/c and the initial water‐to‐solid (binder) mass ratio w/s. Pure cement pastes exhibit w/c = w/s = 0.50 and w/c = w/s = 0.42, respectively. A fly ash‐blended cement paste refers to a cement mass replacement level of 16%, and this is related to w/c = 0.50 and w/s = 0.42. Both unloading moduli and dynamic Young's moduli of all three materials increase practically linearly with increasing hydration degree, in the investigated regime of hydration degrees ranging from 40 to 60%. Fly ash does not contribute significantly to the early‐age hydration of the material, i.e. it represents a quasi‐inert part of the material's microstructure, exhibiting a significant stiffening effect.
Performance of Liaison XL automated immunoassay platform for blood‐borne infection screening on hepatitis B, hepatitis C, HIV 1/2, HTLV 1/2 and Treponema pallidum serological markers
Authors: Malm K. , Kragsbjerg E. , Andersson S. 
Published: March 2015

SUMMARYObjectivesAim of the study was to evaluate performance of a new fully automated platform, DiaSorin‐LIAISON® XL (DiaSorin S.p.A, Vercelli, Italy), in blood donor screening, specifically for hepatitis B surface antigen (HBsAg), hepatitis B core antibodies (anti‐HBc), hepatitis C antibodies (anti‐HCV), HIV p24 antigen, HIV antibodies, human T‐lymphotropic virus types 1 and 2 (HTLV‐1/2) and Treponema pallidum antibodies.BackgroundIn screening for such viral and bacteriological blood‐borne infections, sensitivity and specificity are of utmost importance.MethodsSensitivity was evaluated using selected panels of samples previously analysed on the Abbott Architect immunoanalyser (Abbott Laboratories, Abbott Park, IL, USA) – the gold standard for this evaluation. These samples were confirmed positive for HBsAg, anti‐HBc, anti‐HCV, HIV Ag/Ab, anti‐HTLV‐1/2 and antibodies to T. pallidum, respectively. Specificity analysis was assessed by analysing blood donor samples previously run on the Architect platform and found non‐reactive for each marker. A total of 1·100 donor samples (both new and regular donors) were tested. Previously, non‐specific reactive samples were also run for every tested marker, as well as samples with autoimmune antibodies and antibodies to other infections.ResultsThree hundred seventy‐eight samples positive for the tested markers (HBsAg n = 51, anti‐HBc n = 52, anti‐HCV n = 75, anti‐Treponema n = 55, anti‐HIV‐1 n = 79, anti‐HIV‐2 n = 25, anti‐HIV 1/2 n = 3, anti‐HTLV‐1 n = 28 anti‐HTLV‐2 n = 10) were tested and found positive, suggesting a high sensitivity. A number of 342–1100 negative blood donors (depending on marker) have been tested, with very good specificity for the markers tested, ranging between 99·5 and 100%, respectively.ConclusionsThe LIAISON® XL platform demonstrated very high sensitivity for the markers tested and the specificity necessary to fulfil the stringent requirements for blood donor screening.
Comparison of film measurements and Monte Carlo simulations of dose delivered with very high‐energy electron beams in a polystyrene phantom
Authors: Bazalova‐Carter Magdalena , Liu Michael , Palma Bianey , Dunning Michael , McCormick Doug , Hemsing Erik , Nelson Janice , Jobe Keith , Colby Eric , Koong Albert C. , Tantawi Sami , Dolgashev Valery , Maxim Peter G. , Loo Billy W. 
Published: March 2015

Purpose:To measure radiation dose in a water‐equivalent medium from very high‐energy electron (VHEE) beams and make comparisons to Monte Carlo (MC) simulation results.Methods:Dose in a polystyrene phantom delivered by an experimental VHEE beam line was measured with Gafchromic films for three 50 MeV and two 70 MeV Gaussian beams of 4.0–6.9 mm FWHM and compared to corresponding MC‐simulated dose distributions. MC dose in the polystyrene phantom was calculated with the EGSnrc/BEAMnrc and DOSXYZnrc codes based on the experimental setup. Additionally, the effect of 2% beam energy measurement uncertainty and possible non‐zero beam angular spread on MC dose distributions was evaluated.Results:MC simulated percentage depth dose (PDD) curves agreed with measurements within 4% for all beam sizes at both 50 and 70 MeV VHEE beams. Central axis PDD at 8 cm depth ranged from 14% to 19% for the 5.4–6.9 mm 50 MeV beams and it ranged from 14% to 18% for the 4.0–4.5 mm 70 MeV beams. MC simulated relative beam profiles of regularly shaped Gaussian beams evaluated at depths of 0.64 to 7.46 cm agreed with measurements to within 5%. A 2% beam energy uncertainty and 0.286° beam angular spread corresponded to a maximum 3.0% and 3.8% difference in depth dose curves of the 50 and 70 MeV electron beams, respectively. Absolute dose differences between MC simulations and film measurements of regularly shaped Gaussian beams were between 10% and 42%.Conclusions:The authors demonstrate that relative dose distributions for VHEE beams of 50–70 MeV can be measured with Gafchromic films and modeled with Monte Carlo simulations to an accuracy of 5%. The reported absolute dose differences likely caused by imperfect beam steering and subsequent charge loss revealed the importance of accurate VHEE beam control and diagnostics.
Development of a phantom to validate high‐dose‐rate brachytherapy treatment planning systems with heterogeneous algorithms
Authors: Moura Eduardo S. , Micka John A. , Hammer Cliff G. , Culberson Wesley S. , DeWerd Larry A. , Rostelato Maria Elisa C. M. , Zeituni Carlos A. 
Published: March 2015

Purpose:This work presents the development of a phantom to verify the treatment planning system (TPS) algorithms used for high‐dose‐rate (HDR) brachytherapy. It is designed to measure the relative dose in a heterogeneous media. The experimental details used, simulation methods, and comparisons with a commercial TPS are also provided.Methods:To simulate heterogeneous conditions, four materials were used: Virtual Water™ (VM), BR50/50™, cork, and aluminum. The materials were arranged in 11 heterogeneity configurations. Three dosimeters were used to measure the relative response from a HDR 192Ir source: TLD‐100™, Gafchromic® EBT3 film, and an Exradin™ A1SL ionization chamber. To compare the results from the experimental measurements, the various configurations were modeled in the penelope/penEasy Monte Carlo code. Images of each setup geometry were acquired from a CT scanner and imported into BrachyVision™ TPS software, which includes a grid‐based Boltzmann solver Acuros™. The results of the measurements performed in the heterogeneous setups were normalized to the dose values measured in the homogeneous Virtual Water™ setup and the respective differences due to the heterogeneities were considered. Additionally, dose values calculated based on the American Association of Physicists in Medicine‐Task Group 43 formalism were compared to dose values calculated with the Acuros™ algorithm in the phantom. Calculated doses were compared at the same points, where measurements have been performed.Results:Differences in the relative response as high as 11.5% were found from the homogeneous setup when the heterogeneous materials were inserted into the experimental phantom. The aluminum and cork materials produced larger differences than the plastic materials, with the BR50/50™ material producing results similar to the Virtual Water™ results. Our experimental methods agree with the penelope/penEasy simulations for most setups and dosimeters. The TPS relative differences with the Acuros™ algorithm were similar in both experimental and simulated setups. The discrepancy between the BrachyVision™, Acuros™, and TG‐43 dose responses in the phantom described by this work exceeded 12% for certain setups.Conclusions:The results derived from the phantom measurements show good agreement with the simulations and TPS calculations, using Acuros™ algorithm. Differences in the dose responses were evident in the experimental results when heterogeneous materials were introduced. These measurements prove the usefulness of the heterogeneous phantom for verification of HDR treatment planning systems based on model‐based dose calculation algorithms.
Ceftriaxone-Resistant Salmonella enterica Serotype Typhimurium Sequence Type 313 from Kenyan Patients Is Associated with the
bla
CTX-M-15
Gene on a Novel IncHI2 Plasmid
Authors: Kariuki Samuel , Okoro Chinyere , Kiiru John , Njoroge Samuel , Omuse Geoffrey , Langridge Gemma , Kingsley Robert A. , Dougan Gordon , Revathi Gunturu 
Published: March 2015

ABSTRACT

Multidrug-resistant bacteria pose a major challenge to the clinical management of infections in resource-poor settings. Although nontyphoidal
Salmonella
(NTS) bacteria cause predominantly enteric self-limiting illness in developed countries, NTS is responsible for a huge burden of life-threatening bloodstream infections in sub-Saharan Africa. Here, we characterized nine
S
. Typhimurium isolates from an outbreak involving patients who initially failed to respond to ceftriaxone treatment at a referral hospital in Kenya. These
Salmonella enterica
serotype Typhimurium isolates were resistant to ampicillin, chloramphenicol, cefuroxime, ceftriaxone, aztreonam, cefepime, sulfamethoxazole-trimethoprim, and cefpodoxime. Resistance to β-lactams, including to ceftriaxone, was associated with carriage of a combination of
bla
CTX-M-15
,
bla
OXA-1
, and
bla
TEM-1
genes. The genes encoding resistance to heavy-metal ions were borne on the novel IncHI2 plasmid pKST313, which also carried a pair of class 1 integrons. All nine isolates formed a single clade within
S
. Typhimurium ST313, the major clone of an ongoing invasive NTS epidemic in the region. This emerging ceftriaxone-resistant clone may pose a major challenge in the management of invasive NTS in sub-Saharan Africa.
Artemisinin-Resistant Plasmodium falciparum Parasites Exhibit Altered Patterns of Development in Infected Erythrocytes
Authors: Hott Amanda , Casandra Debora , Sparks Kansas N. , Morton Lindsay C. , Castanares Geocel-Grace , Rutter Amanda , Kyle Dennis E. 
Published: March 2015

ABSTRACT

Artemisinin derivatives are used in combination with other antimalarial drugs for treatment of multidrug-resistant malaria worldwide. Clinical resistance to artemisinin recently emerged in southeast Asia, yet
in vitro
phenotypes for discerning mechanism(s) of resistance remain elusive. Here, we describe novel phenotypic resistance traits expressed by artemisinin-resistant
Plasmodium falciparum
. The resistant parasites exhibit altered patterns of development that result in reduced exposure to drug at the most susceptible stage of development in erythrocytes (trophozoites) and increased exposure in the most resistant stage (rings). In addition, a novel
in vitro
delayed clearance assay (DCA) that assesses drug effects on asexual stages was found to correlate with parasite clearance half-life
in vivo
as well as with mutations in the Kelch domain gene associated with resistance (Pf3D7_1343700). Importantly, all of the resistance phenotypes were stable in cloned parasites for more than 2 years without drug pressure. The results demonstrate artemisinin-resistant
P. falciparum
has evolved a novel mechanism of phenotypic resistance to artemisinin drugs linked to abnormal cell cycle regulation. These results offer insights into a novel mechanism of drug resistance in
P. falciparum
and new tools for monitoring the spread of artemisinin resistance.
Subtype-Specific Analysis of the K65R Substitution in HIV-1 That Confers Hypersusceptibility to a Novel Nucleotide-Competing Reverse Transcriptase Inhibitor
Authors: Xu Hong-Tao , Colby-Germinario Susan P. , Quashie Peter K. , Bethell Richard , Wainberg Mark A. 
Published: March 2015

ABSTRACTCompound A is a novel nucleotide-competing HIV-1 reverse transcriptase (RT) inhibitor (NcRTI) that selects for a unique W153L substitution that confers hypersusceptibility to tenofovir, while the K65R substitution in RT confers resistance against tenofovir and enhances susceptibility to NcRTIs. Although the K65R substitution is more common in subtype C viruses, the impact of subtype variability on NcRTI susceptibility has not been studied. In the present study, we performed experiments with compound A by using purified recombinant RT enzymes and viruses of subtypes B and C and circulating recombinant form CRF_A/G. We confirmed the hypersusceptibility of K65R substitution-containing RTs to compound A for subtype C, CRF_A/G, and subtype B. Steady-state kinetic analysis showed that K65R RTs enhanced the susceptibility to compound A by increasing binding of the inhibitor to the nucleotide binding site of RT in a subtype-independent manner, without significantly discriminating against the natural nucleotide substrate. These data highlight the potential utility of NcRTIs, such as compound A, for treatment of infections with K65R substitution-containing viruses, regardless of HIV-1 subtype.
Predominance of KPC-3 in a Survey for Carbapenemase-Producing Enterobacteriaceae in Portugal
Authors: Manageiro Vera , Ferreira Eugénia , Almeida Joana , Barbosa Stephanie , Simões Constança ,   Antibiotic Resistance Surveillance Program in Portugal (ARSIP), Bonomo Robert A. , Caniça Manuela 
Published: March 2015

ABSTRACT

Among the 2,105
Enterobacteriaceae
tested in a survey done in Portugal, 165 were nonsusceptible to carbapenems, from which 35 (26
Klebsiella pneumoniae
, 3
Escherichia coli
, 2
Enterobacter aerogenes
, and 3
Enterobacter cloacae
isolates and 1
Klebsiella oxytoca
isolate) were confirmed to be carbapenemase producers by the presence of 30
Tn
4401d-
bla
KPC-3
, 4
intI
3-
bla
GES-5
, and one
intI
1-
bla
VIM-2
gene, alone or in combination with other
bla
genes. The dissemination of
bla
KPC-3
gene carried by an IncF plasmid suggests lateral gene transfer as a major mechanism of dissemination.
Characterization of CPAF Critical Residues and Secretion during Chlamydia trachomatis Infection
Authors: Yang Zhangsheng , Tang Lingli , Sun Xin , Chai Jijie , Zhong Guangming 
Published: March 2015

ABSTRACT

CPAF (chlamydial protease-like activity factor), a
Chlamydia
serine protease, is activated via proximity-induced intermolecular dimerization that triggers processing and removal of an inhibitory peptide occupying the CPAF substrate-binding groove. An active CPAF is a homodimer of two identical intramolecular heterodimers, each consisting of 29-kDa N-terminal and 35-kDa C-terminal fragments. However, critical residues for CPAF intermolecular dimerization, catalytic activity, and processing were defined in cell-free systems. Complementation of a CPAF-deficient chlamydial organism with a plasmid-encoded CPAF has enabled us to characterize CPAF during infection. The transformants expressing CPAF mutated at intermolecular dimerization, catalytic, or cleavage residues still produced active CPAF, although at a lower efficiency, indicating that CPAF can tolerate more mutations inside
Chlamydia
-infected cells than in cell-free systems. Only by simultaneously mutating both intermolecular dimerization and catalytic residues was CPAF activation completely blocked during infection, both indicating the importance of the critical residues identified in the cell-free systems and exploring the limit of CPAF's tolerance for mutations in the intracellular environment. We further found that active CPAF was always detected in the host cell cytoplasm while nonactive CPAF was restricted to within the chlamydial inclusions, regardless of how the infected cell samples were treated. Thus, CPAF translocation into the host cell cytoplasm correlates with CPAF enzymatic activity and is not altered by sample treatment conditions. These observations have provided new evidence for CPAF activation and translocation, which should encourage continued investigation of CPAF in chlamydial pathogenesis.
Colony Morphology Variation of Burkholderia pseudomallei Is Associated with Antigenic Variation and O-Polysaccharide Modification
Authors: Wikraiphat Chanthiwa , Saiprom Natnaree , Tandhavanant Sarunporn , Heiss Christian , Azadi Parastoo , Wongsuvan Gumphol , Tuanyok Apichai , Holden Matthew T. G. , Burtnick Mary N. , Brett Paul J. , Peacock Sharon J. , Chantratita Narisara 
Published: March 2015

ABSTRACT

Burkholderia pseudomallei
is a CDC tier 1 select agent that causes melioidosis, a severe disease in humans and animals. Persistent infections are common, and there is currently no vaccine available. Lipopolysaccharide (LPS) is a potential vaccine candidate.
B. pseudomallei
expresses three serologically distinct LPS types. The predominant O-polysaccharide (OPS) is an unbranched heteropolymer with repeating
d
-glucose and 6-deoxy-
l
-talose residues in which the 6-deoxy-
l
-talose residues are variably replaced with
O
-acetyl and
O
-methyl modifications. We observed that primary clinical
B. pseudomallei
isolates with mucoid and nonmucoid colony morphologies from the same sample expressed different antigenic types distinguishable using an LPS-specific monoclonal antibody (MAb). MAb-reactive (nonmucoid) and nonreactive (mucoid) strains from the same patient exhibited identical LPS banding patterns by silver staining and indistinguishable genotypes. We hypothesized that LPS antigenic variation reflected modification of the OPS moieties. Mutagenesis of three genes involved in LPS synthesis was performed in
B. pseudomallei
K96243. Loss of MAb reactivity was observed in both
wbiA
(encoding a 2-
O
-acetyltransferase) and
wbiD
(putative methyl transferase) mutants. The structural characteristics of the OPS moieties from isogenic nonmucoid strain 4095a and mucoid strain 4095c were further investigated. Utilizing nuclear magnetic resonance (NMR) spectroscopy, we found that
B. pseudomallei
4095a and 4095c OPS antigens exhibited substitution patterns that differed from the prototypic OPS structure. Specifically, 4095a lacked 4-
O
-acetylation, while 4095c lacked both 4-
O
-acetylation and 2-
O
-methylation. Our studies indicate that
B. pseudomallei
OPS undergoes antigenic variation and suggest that the 9D5 MAb recognizes a conformational epitope that is influenced by both
O
-acetyl and
O
-methyl substitution patterns.
Structural Determinants of the Interaction between the TpsA and TpsB Proteins in the Haemophilus influenzae HMW1 Two-Partner Secretion System
Authors: Grass Susan , Rempe Katherine A. , St. Geme Joseph W. 
Published: March 2015

ABSTRACT

The two-partner secretion (TPS) pathway in Gram-negative bacteria consists of a TpsA exoprotein and a cognate TpsB outer membrane pore-forming translocator protein. Previous work has demonstrated that the TpsA protein contains an N-terminal TPS domain that plays an important role in targeting the TpsB protein and is required for secretion. The nontypeable
Haemophilus influenzae
HMW1 and HMW2 adhesins are homologous proteins that are prototype TpsA proteins and are secreted by the HMW1B and HMW2B TpsB proteins. In the present study, we sought to define the structural determinants of HMW1 interaction with HMW1B during the transport process and while anchored to the bacterial surface. Modeling of HMW1B revealed an N-terminal periplasmic region that contains two polypeptide transport-associated (POTRA) domains and a C-terminal membrane-localized region that forms a pore. Biochemical studies demonstrated that HMW1 engages HMW1B via interaction between the HMW1 TPS domain and the HMW1B periplasmic region, specifically, the predicted POTRA1 and POTRA2 domains. Subsequently, HMW1 is shuttled to the HMW1B pore, facilitated by the N-terminal region, the middle region, and the NPNG motif in the HMW1 TPS domain. Additional analysis revealed that the interaction between HMW1 and HMW1B is highly specific and is dependent upon the POTRA domains and the pore-forming domain of HMW1B. Further studies established that tethering of HMW1 to the surface-exposed region of HMW1B is dependent upon the external loops of HMW1B formed by residues 267 to 283 and residues 324 to 330. These observations may have broad relevance to proteins secreted by the TPS pathway.

IMPORTANCE
Secretion of HMW1 involves a recognition event between the extended form of the HMW1 propiece and the HMW1B POTRA domains. Our results identify specific interactions between the HMW1 propiece and the periplasmic HMW1B POTRA domains. The results also suggest that the process of HMW1 translocation involves at least two discrete steps, including initial interaction between the HMW1 propiece and the HMW1B POTRA domains and then a separate translocation event. We have also discovered that the HMW1B pore itself appears to influence the translocation process. These observations extend our knowledge of the two-partner secretion system and may be broadly relevant to other proteins secreted by the TPS pathway.