Emergence of a Non-Van der Waals Magnetic Phase in a Van der Waals Ferromagnet.

Manipulation of long-range order in 2D van der Waals (vdW) magnetic materials (e.g., CrI3 , CrSiTe3 ,etc.), exfoliated in few-atomic layer, can be achieved via application of electric field, mechanical-constraint, interface engineering, or even by chemical substitution/doping. Usually, active surface oxidation due to the exposure in the ambient condition and hydrolysis in the presence of water/moisture causes degradation in magnetic nanosheets that, in turn, affects the nanoelectronic /spintronic device performance. Counterintuitively, the current study reveals that exposure to the air at ambient atmosphere results in advent of a stable nonlayered secondary ferromagnetic phase in the form of Cr2 Te3 (TC2 ≈160 K) in the parent vdW magnetic semiconductor Cr2 Ge2 Te6 (TC1 ≈69 K). The coexistence of the two ferromagnetic phases in the time elapsed bulk crystal is confirmed through systematic investigation of crystal structure along with detailed dc/ac magnetic susceptibility, specific heat, and magneto-transport measurement. To capture the concurrence of the two ferromagnetic phases in a single material, Ginzburg-Landau theory with two independent order parameters (as magnetization) with a coupling term can be introduced. In contrast to the rather common poor environmental stability of the vdW magnets, the results open possibilities of finding air-stable novel materials having multiple magnetic phases.

Diagnosis of erythema nodosum leprosum (type 2 reaction) by cytology.

OBJECTIVE: It was the aim of this study to evaluate the possible role of cytology in erythema nodosum leprosum (ENL) and its use for early treatment of the disease. STUDY DESIGN: We present a prospective study conducted with 15 clinically diagnosed ENL cases. Among them, 13 cases had previously been diagnosed with lepromatous leprosy (LL) and 2 patients were new LL cases with signs and symptoms of ENL lesions. Haematoxylin and eosin stain with modified Ziehl-Neelsen stain was performed on fine needle aspiration material. One case was sent for biopsy. RESULTS: Complete cytological diagnosis of ENL was done in all 15 cases. Histopathological study revealed classical ENL lesions which also showed ENL features in cytodiagnosis. CONCLUSION: In the past, the accurate mode of diagnosis of ENL lesions was histopathology. However, clinicians have to wait a long time for the report and generally they start treatment only on the basis of clinical signs and symptoms. Cytodiagnosis of ENL lesions is an early, effective method for accurate diagnosis and helps to initiate treatment for these painful lesions.

Low-density lipoprotein particle profiles compared with standard lipids measurements in the association with asymptomatic intracranial artery stenosis.

The Shiga Epidemiological Study of Subclinical Atherosclerosis was conducted in Kusatsu City, Shiga, Japan, from 2006 to 2008. Participants were measured for LDL-p through nuclear magnetic resonance technology. 740 men participated in follow-up and underwent 1.5 T brain magnetic resonance angiography from 2012 to 2015. Participants were categorized as no-ICAS, and ICAS consisted of mild-ICAS (1 to < 50%) and severe-ICAS (≥ 50%) in any of the arteries examined. After exclusion criteria, 711 men left for analysis, we used multiple logistic regression to examine the association between lipid profiles and ICAS prevalence. Among the study participants, 205 individuals (28.8%) had ICAS, while 144 individuals (20.3%) demonstrated discordance between LDL-c and LDL-p levels. The discordance "low LDL-c-high LDL-p" group had the highest ICAS risk with an adjusted OR (95% CI) of 2.78 (1.55-5.00) in the reference of the concordance "low LDL-c-low LDL-p" group. This was followed by the concordance "high LDL-c-high LDL-p" group of 2.56 (1.69-3.85) and the discordance "high LDL-c-low LDL-p" group of 2.40 (1.29-4.46). These findings suggest that evaluating LDL-p levels alongside LDL-c may aid in identifying adults at a higher risk for ICAS.

Mechanisms for the formation of acenes from α-diketones by bisdecarbonylation.

The bisdecarbonylation of bridged α-diketones has turned into an important reaction for the photochemical generation of higher acenes, in particular under matrix isolation conditions. Here, a computational mechanistic analysis of the bisdecarbonylation of dibenzobicyclo[2.2.2]octadienedione 2 to anthracene 1 is presented. The study employed the B3LYP functional in conjunction with the 6-311+G** basis set for geometry optimization on the S0, S1, and T1 potential energy surfaces as well as coupled cluster [CCSD(T)] and second-order multireference perturbation theory (MRMP2) with the cc-pVDZ basis set for evaluation of energies of intermediates and transition states. The first step of the most favorable pathway on the T1 surface has a barrier of 12 kcal mol(­1) with respect to the T1 minimum 2-3B1 and involves cleavage of the C­C bond between the bridgehead and one carbonyl atom, C(bridge)­C(O), yielding a biradical intermediate (INT1-T). On the S1 surface, the analogous step only has a barrier of less than 4 kcal mol(­1). A conical intersection of the S1 with the S0 surface exists after the transition state and provides a means for relaxation to a biradical intermediate (INT1-S) on the S0 surface. The concerted loss of two CO molecules from INT1-S has only a very small barrier. Similarly, consecutive loss of two CO molecules from the triplet state of this diradical (INT1-T) to give triplet anthracene is more favorable than ejection of triplet ethylenedione. Thus, the features identified computationally on the S0, S1, and T1 potential energy surface agree with earlier experimental observations of a fast photobisdecarbonylation within 7 ns from the triplet and singlet states of 2 and a lack of triplet ethylenedione formation.

Low physical activity among middle-aged type-2 diabetic outpatients of two peripheral hospitals in Bangladesh.

Physical activity (PA) is an important lifestyle recommendation for managing type-2 diabetes mellitus (T2DM). However, low PA among them is a global public health concern, including Bangladesh. We aimed to investigate the prevalence of low PA levels and its associated sociodemographic factors particularly among middle-aged T2DM subjects, which is quite limited globally and unknown in Bangladesh. In this cross-sectional study, we conveniently recruited 356 T2DM subjects (aged 40-60 years) from outpatient departments of the corresponding diabetic hospitals from Pirojpur and Dinajpur, the southern and northern districts, respectively. The primary outcome was low PA (via metabolic equivalents <600), using the Global Physical Activity Questionnaire. Univariable and multivariable binary logistic regression analyses were used to identify the factors associated with low PA. Among the participants (mean age 51.0±6.9 years), men and women were with almost equal proportions (48.9% and 51.1%, respectively). The prevalence (95% Confidence Intervals [CI]) of low PA was 34.8% (29.9-39.7). The median sitting or reclining time was 6 hours on a typical day. The odds (OR [95% CI]; P) of low PA was found to be significantly higher in respondents with primary or no education compared to the above-primary level, in unadjusted (1.6 [1.1-2.6]; 0.029) and adjusted (2.0 [1.1-3.7]; 0.028) associations both. In conclusion, over one-third of the middle-aged study subjects had a low PA level, which was associated with education. There is a high demand for designing and implementing PA enhancing interventions among them.

Intercropping with Pigeonpea (Cajanus cajan L. Millsp.): An Assessment of Its Influence on the Assemblage of Pollinators and Yield of Neighbouring Non-Leguminous Crops.

Intercropping is practiced in modern intensive agriculture considering many benefits, including additive crop yield. However, it may have competitive or facilitative interactions between pollinator-dependant crops. Here, we investigated the reproductive aspects of pigeonpea (Cajanus cajan). We assessed the influence of blooming pigeonpea on pollinator's assemblage and the yield of neighbouring non-leguminous crops (e.g., coriander, mustard). For these, we recorded floral visitors and the yield of the targeted crops from two types of fields-closely situated and distantly situated concerning pigeonpea plantation. Pigeonpea is autogamous, but pollinator's visits enhance fruit and seed sets. Bright, nectariferous flowers emitted several volatile organic compounds and were visited by numerous insect species. The prime pollinators of pigeonpea are carpenter bees and leafcutter bees. In contrast, halictidae, honeybees and stingless bees mainly pollinate the co-blooming non-leguminous crops (coriander and mustard). The richness and abundance of pollinators on these co-blooming crops remain similar in closely situated and distantly situated fields. As a result, the yield of the neighbouring crops is not significantly influenced by the blooming pigeonpea. Therefore, it can be concluded that planting pigeonpea in ridges of agricultural fields will be an additional agricultural output without affecting the assemblage of pollinators and yields of neighbouring co-blooming crops.

Association of exposure to salinity in groundwater with chronic kidney disease among diabetic population in Bangladesh.

Globally, chronic kidney disease (CKD) is one of the major public health concerns. CKD and renal failure are reported to be high in the areas with higher salinity, however, the association is still unclear. We aimed at assessing the association of degree of groundwater salinity with CKD among diabetic populations of two selected areas in Bangladesh. This cross-sectional analytic study was carried out among 356 diabetic patients aged 40-60 years in high groundwater salinity exposed Pirojpur (n = 151) and non-exposed Dinajpur (n = 205), the southern and northern districts of Bangladesh, respectively. The primary outcome was the presence of CKD (via estimated glomerular filtration rate <60 ml/min) using Modification of Diet in Renal Disease equation. Binary logistic regression analyses were done. In non-exposed (mean age 51.2±6.9 years) and exposed (mean age 50.8±6.9 years) respondents, men (57.6%) and women (62.9%) were predominant, respectively. The proportion of patients with CKD was found to be higher in the exposed group than that of the non-exposed group (33.1% vs. 26.8%; P 0.199). The odds (OR [95% confidence interval]; P) of CKD were not found to be significantly higher in high salinity exposed respondents (1.35 [0.85-2.14]; 0.199), compared to the non-exposed. However, the odds of hypertension were found to be significantly higher in high salinity exposed respondents (2.10 [1.37-3.23]; 0.001), compared to the non-exposed. And, the interaction of high salinity and hypertension showed a significant association with CKD (P = 0.009). In conclusion, the findings suggest that groundwater salinity may not be directly associated with CKD in southern Bangladesh, however, it may have an indirect association with the disorder through the association of hypertension with groundwater salinity. Further large scaled studies are required to answer the research hypothesis more clearly.

Protective intravenous BCG vaccination induces enhanced immune signaling in the airways.

Intradermal (ID) Bacillus Calmette-Guérin (BCG) is the most widely administered vaccine in the world. However, ID-BCG fails to achieve the level of protection needed in adults to alter the course of the tuberculosis epidemic. Recent studies in non-human primates have demonstrated high levels of protection against Mycobacterium tuberculosis ( Mtb ) following intravenous (IV) administration of BCG. However, the protective immune features that emerge following IV BCG vaccination remain incompletely defined. Here we used single-cell RNA-sequencing (scRNAseq) to transcriptionally profile 157,114 unstimulated and purified protein derivative (PPD)-stimulated bronchoalveolar lavage (BAL) cells from 29 rhesus macaques immunized with BCG across routes of administration and doses to uncover cell composition-, gene expression-, and biological network-level signatures associated with IV BCG-mediated protection. Our analyses revealed that high-dose IV BCG drove an influx of polyfunctional T cells and macrophages into the airways. These macrophages exhibited a basal activation phenotype even in the absence of PPD-stimulation, defined in part by IFN and TNF-α signaling up to 6 months following BCG immunization. Furthermore, intercellular immune signaling pathways between key myeloid and T cell subsets were enhanced following PPD-stimulation in high-dose IV BCG-vaccinated macaques. High-dose IV BCG also engendered quantitatively and qualitatively stronger transcriptional responses to PPD-stimulation, with a robust Th1-Th17 transcriptional phenotype in T cells, and augmented transcriptional signatures of reactive oxygen species production, hypoxia, and IFN-γ response within alveolar macrophages. Collectively, this work supports that IV BCG immunization creates a unique cellular ecosystem in the airways, which primes and enables local myeloid cells to effectively clear Mtb upon challenge.

Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives.

Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone--due to an increase in the polymer ionization potential--while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2':5',2''-terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current.

The importance of dye chemistry and TiCl4 surface treatment in the behavior of Al2O3 recombination barrier layers deposited by atomic layer deposition in solid-state dye-sensitized solar cells.

Atomic layer deposition (ALD) was used to fabricate Al(2)O(3) recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al(2)O(3) recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 µm-thick nanoporous TiO(2) active layer and the HTM spiro-OMeTAD. The impact of Al(2)O(3) barriers was also studied in devices employing different dyes, with increased active layer thicknesses, and with substrates that did not undergo the TiCl(4) surface treatment. In all instances, electron lifetimes (as determined by transient photovoltage measurements) increased and dark current was suppressed after Al(2)O(3) deposition. However, only when the TiCl(4) treatment was eliminated did device efficiency increase; in all other instances efficiency decreased due to a drop in short-circuit current. These results are attributed in the former case to the similar effects of Al(2)O(3) ALD and the TiCl(4) surface treatment whereas the insulating properties of Al(2)O(3) hinder charge injection and lead to current loss in TiCl(4)-treated devices. The impact of Al(2)O(3) barrier layers was unaffected by doubling the active layer thickness or using an alternative ruthenium dye, but a metal-free donor-π-acceptor dye exhibited a much smaller decrease in current due to its higher excited state energy. We develop a model employing prior research on Al(2)O(3) growth and dye kinetics that successfully predicts the reduction in device current as a function of ALD cycles and is extendable to different dye-barrier systems.

Shubnikov-de Haas and de Haas-van Alphen oscillations in Czochralski grown CoSi single crystal.

Anisotropic transport, Shubnikov-de Haas (SdH), and de Haas-van Alphen (dHvA) quantum oscillations studies are reported on a high-quality CoSi single crystal grown by the Czochralski method. Temperature-dependent resistivities indicate the dominating electron-electron scattering. Magnetoresistance (MR) at 2 K reaches 610% forI ∥ [111]andB ∥ [011-], whereas it is 500% forI ∥ [011-] andB ∥ [111]. A negative slope in field-dependent Hall resistivity suggests electrons are the majority carriers. The carrier concentration extracted from Hall conductivity indicates no electron-hole compensation. In 3D CoSi, the electron transport lifetime is found to be approximately in the same order as the quantum lifetime, whereas in 2Delectron gas the long-range scattering drives the transport life much larger than the quantum lifetime. From MR and Hall SdH oscillations, the effective masses and Dingle temperatures have been calculated. The dHvA oscillation reveals three frequencies at 18 T (γ), 558 T (α) and 663 T (ß), whereas, SdH oscillation results in only two frequenciesαandß. Theγfrequency observed in dHvA oscillation is a tiny hole pocket at the Γ point.

3,4-Disubstituted polyalkylthiophenes for high-performance thin-film transistors and photovoltaics.

We demonstrate that poly(3,4-dialkylterthiophenes) (P34ATs) have comparable transistor mobilities (0.17 cm(2) V(-1) s(-1)) and greater environmental stability (less degradation of on/off ratio) than regioregular poly(3-alkylthiophenes) (P3ATs). Unlike poly(3-hexylthiophene) (P3HT), P34ATs do not show a strong and distinct π-π stacking in X-ray diffraction. This suggests that a strong π-π stacking is not always necessary for high charge-carrier mobility and that other potential polymer packing motifs in addition to the edge-on structure (π-π stacking direction parallel to the substrate) can lead to a high carrier mobility. The high charge-carrier mobilities of the hexyl and octyl-substituted P34AT produce power conversion efficiencies of 4.2% in polymer:fullerene bulk heterojunction photovoltaic devices. An enhanced open-circuit voltage (0.716-0.771 eV) in P34AT solar cells relative to P3HT due to increased ionization potentials was observed.

Cardiovascular risk assessment among type-2 diabetic subjects in selected areas of Bangladesh: concordance among without cholesterol-based WHO/ISH, Globorisk, and Framingham risk prediction tools.

INTRODUCTION: Cardiovascular disease (CVD) risk is higher among the subjects with type-2 diabetes mellitus (T2DM) in low- and middle-income countries, like Bangladesh. However, there is no relevant available online published data for this country. We aimed at assessing the 10-year CVD risk among T2DM subjects in selected areas of Bangladesh using the without cholesterol-based joint World Health Organization/International Society of Hypertension (WHO/ISH), Globorisk, and Framingham Risk Score (FRS) risk prediction tools, and also evaluating the concordance among these tools. METHODS AND MATERIALS: In this paper, we extracted a total of 327 subjects (40-60 years aged) from an observational study with 356 subjects, excluding those with diagnosed CVDs. The subjects were selected conveniently from purposively selected respective diabetic hospitals of Pirojpur and Dinajpur districts. We used the required respective variables of WHO/ISH, Globorisk, and FRS tools to predict CVD risks. The risks were categorized as low (<10%), moderate (10-<20%), high (20-<30%) and very high (≥30%). RESULTS: Subjects at moderate CVD risk were much higher identified by Globorisk (37.0%) and FRS (38.8%) compared to WHO/ISH (15.3%), and the same scenarios have also been observed for high (13.5%, 19.3% and 2.4%, respectively) and very high (5.5%, 17.4% and 1.8%, respectively) risks. There was fair level of concordance between WHO/ISH and Globorisk (PABAK-OS k = 0.37; 95% CI 0.33-0.42; P < 0.001), and Globorisk and FRS (PABAK-OS k = 0.34; 95% CI 0.30-0.39; P < 0.001). And, between WHO/ISH and FRS, it was none to slight level (PABAK-OS k = 0.09, 95% CI 0.04-0.14; P = 0.001). CONCLUSIONS: A significant proportion of the selected study subjects is at moderate to very high risk of developing CVDs predicted especially by Globorisk and FRS compared to WHO/ISH, indicating low concordance. With and without cholesterol-based studies can answer the problem more clearly.

Evolution of local structure and superconductivity in CaFe2As2.

We investigate the evolution of the local structural parameters and their implication in unconventional superconductivity of 122 class of materials employing extended x-ray absorption fine structure studies. The spectral functions near the FeK- and AsK-absorption edges of CaFe2As2and its superconducting composition, CaFe1.9Co0.1As2(Tc= 12 K) exhibit evidence of enhancement of Fe contributions near the Fermi level with Co substitution, which becomes more prominent at low temperatures indicating enhanced role of Fe in the electronic properties with doping. As-Fe and Fe-Fe bondlengths derived from the experimental data reveal evolution with temperature across the magneto-structural transition in the parent compound. The evolution of these parameters in Co-doped superconducting composition is similar to its parent compound although no magneto-structural transition is observed in this system. These results reveal an evidence of doping induced evolution to the proximity to critical behavior and/or strong nematic fluctuations which might be important for superconductivity in this system.

Effect of Chronotherapy of Antihypertensives in Chronic Kidney Disease: A Randomized Control Trial.

INTRODUCTION: There is a higher prevalence of non-dipping pattern in hypertensive chronic kidney disease (CKD) patients. Nocturnal hypertension has been shown to predict cardiovascular mortality and morbidity and is often superior to daytime blood pressure. We studied the effect of shifting or adding antihypertensive to night time on blood pressure profile of CKD III-IV patients. METHODS: In this single-center, prospective, randomized controlled trial, eligible participants were adults from eastern India aged 18-65 years with CKD stages 3 and 4, with a non-dipping pattern on ambulatory blood pressure monitor (ABPM). The intervention group received all the antihypertensives in the night time whereas the standard care group continued to take the medication in the morning. Both groups were followed up for 1 year. The primary outcome was the number of patients changed from non-dippers to dippers in the standard care group and intervention group. Secondary outcomes included a change in estimated glomerular filtration rate (eGFR) and change in the cardiac structure. RESULTS: 39 patients in the intervention group and 36 patients in the standard care group were analyzed. 10 patients (26%) reverted to dipping pattern in the intervention group as compared to none in the standard care group. Mean changes in eGFR were -2.55 and -0.18 mL/min/1.73 m2 in the standard care and intervention group at the end of the study, respectively. Between-group difference in eGFR was significant at 1 year (5.22 [95% CI, 4.3-6.1] ml/min/1.73 m2); (P = 0.03). The cardiac structure showed no significant changes in either group. CONCLUSIONS: Bedtime administration of antihypertensives reverted non-dippers to dippers and slowed the decline in eGFR in CKD stages 3 and 4 compared to morning administration of antihypertensives.

Magnetotransport properties of noncentrosymmetric CaAgBi single crystal.

We report on the single crystal growth and transport properties of a topological semimetal CaAgBi which crystallizes in the hexagonal ABC-type structure with the non-centrosymmetric space group P63 mc (No. 186). The transverse magnetoresistance measurements with current in the basal plane of the hexagonal crystal structure reveal a value of about 30% for I∥[10̄0] direction and about 50% for I∥[1̅10] direction at 10 K in an applied magnetic field of 14 T. The magnetoresistance shows a cusp-like behavior in the low magnetic field region, suggesting the presence of weak antilocalization effect for temperatures less than 100 K. The Hall measurements reveal that predominant charge carriers are p-type, exhibiting a linear behavior at high fields. The magnetoconductance of CaAgBi is analyzed based on the modified Hikami-Larkin-Nagaoka model. Our first-principle calculations within a density-functional theory framework reveal that the Fermi surface of CaAgBi consists of both the electron and hole pockets and the size of the hole pocket is much larger than electron pockets suggesting the dominant p-type carriers in accordance with our experimental results.

Risk of diabetic foot ulcer and its associated factors among Bangladeshi subjects: a multicentric cross-sectional study.

OBJECTIVE: To assess the risk of diabetic foot ulcer (DFU) and find out its associated factors among subjects with type 2 diabetes (T2D) of Bangladesh. DESIGN, SETTING AND PARTICIPANTS: This cross-sectional study recruited 1200 subjects with T2D who visited 16 centres of Health Care Development Project run by Diabetic Association of Bangladesh. PRIMARY AND SECONDARY OUTCOME MEASURES: Risk of DFU was assessed using a modified version of International Working Group on the Diabetic Foot (IWGDF) Risk Classification System. The modified system was based on five parameters, namely peripheral neuropathy (PN), peripheral arterial diseases (PAD), deformity, ulcer history and amputation. The risks were categorised as group 0 (no PN, no PAD), group 1 (PN, no PAD and no deformity), group 2A (PN and deformity, no PAD), group 2B (PAD), group 3A (ulcer history) and group 3B (amputation). The associated factors of DFU risk were determined using multinomial logistic regression for each risk category separately. RESULTS: Overall, 44.5% of the subjects were found 'at risk' of DFU. This risk was higher among men (45.6%) than women and among those who lived in rural areas (45.5%) as compared with the urban population. According to IWGDF categories, the risk was distributed as 55.5%, 4.2%, 11.6%, 0.3%, 20.6% and 7.9% for group 0, group 1, group 2A, group 2B, group 3A and group 3B, respectively. The associated factors of DFU (OR >1) were age ≥50 years, rural area, low economic status, insulin use, history of trauma, diabetic retinopathy and diabetic nephropathy. CONCLUSION: A significant number of the subjects with T2D under study were at risk of DFU, which demands an effective screening programme to reduce DFU-related morbidity and mortality.

Efficient Silver Release From Ion Exchange Silver Dressings in Biologically Relevant Media.

INTRODUCTION: Silver-containing wound dressings commonly are used when there is a risk of infection. These commercial antimicrobial silver dressings have various compositions that use different substrates and/or silver sources. Common silver sources are ionic silver (Ag+) and metallic silver (Ag0). A third source of silver is ion exchange silver compounds (Ag+ complex), in which silver ions are encapsulated in an inorganic carrier to moderate the availability of the silver ions and are released via an ion exchange mechanism. OBJECTIVE: In this study, silver release of different types of silver dressings (Ag+, Ag0, Ag+ complex) in biologically relevant media is investigated. MATERIALS AND METHODS: Simulated wound fluid (SWF) and SWF in combination with 5% bovine serum albumin were used as the extraction media. RESULTS: The composition of the extraction media was found to strongly affect the release of silver. The silver released from most silver dressings peaked at ca 0.5 ppm of soluble silver without any protein in the extraction media. Apparent equilibria established between silver and the salts used for SWF were disrupted by the presence of the protein. This resulted in a dramatic increase in silver release over ionic solutions in the absence of the protein. Dressings differed dramatically in their silver release efficiency. The nature of the silver played a more significant role than the silver content in the dressings. CONCLUSIONS: The ion exchange (Ag+ complex) silver dressing was shown to be the most efficient among all the dressings tested for silver release.

Synthesis, stability, and photochemistry of pentacene, hexacene, and heptacene: a matrix isolation study.

The photochemical bisdecarbonylation of bridged alpha-diketones (Strating-Zwanenburg reaction) to give the oligoacenes pentacene (2), hexacene (3), and heptacene (4) is investigated in solid inert gas matrices at cryogenic temperatures. The photodecomposition using visible light irradiation cleanly produces the corresponding oligoacene without formation of observable intermediates. This synthetic approach to the higher acenes allows a comprehensive comparative study of their electronic absorption and infrared spectral properties under identical conditions for the first time. In addition, the route makes it possible to investigate the thermal and photochemical stability of these higher acenes and addresses the problem of heptacene stability which dates back almost 70 years. This largest known member of the acene series is found to be unstable at room temperature. Furthermore, all oligoacenes 2-4 undergo a photoredox reaction upon 185 nm excitation, resulting in the concurrent formation of radical cations and anions in the noble gas matrix. These polaron states of the oligoacenes are stable under the conditions of their generation but collapse to the uncharged acenes upon visible light irradiation.