Cracking under Internal Pressure: Photodynamic Behavior of Vinyl Azide Crystals through N2 Release.

When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (1a), 3-azido-1-(4-methoxyphenyl)propenone (1b), and 3-azido-1-(4-chlorophenyl)propenone (1c) exhibit dramatic mechanical effects by cracking or bending with the release of N2. Mechanistic studies using laser flash photolysis, supported by quantum mechanical calculations, show that each of the vinyl azides degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, the three compounds exhibit distinct photomechanical responses in bulk crystals. While the crystals of 1a delaminate and release gaseous N2 indiscriminately under paraffin oil, the crystals of 1b and 1c visibly expand, bend, and fracture, mainly along specific crystallographic faces, before releasing N2. The photochemical analysis suggests that the observed expansion is due to internal pressure exerted by the gaseous product in the crystal lattices of these materials. Lattice energy calculations, supported by nanoindentation experiments, show significant differences in the respective lattice energies. The calculations identify critical features in the crystal structures of 1b and 1c where elastic energy accumulates during gas release, which correspond to the direction of the observed cracks. This study highlights the hitherto untapped potential of photochemical gas release to elicit a photomechanical response and motility of photoreactive molecular crystals.

Comparison of the Photochemistry of Acyclic and Cyclic 4-(4-Methoxy-phenyl)-4-oxo-but-2-enoate Ester Derivatives.

To clarify the cis-trans isomerization mechanism of simple alkenes on the triplet excited state surface, the photochemistry of acyclic and cyclic vinyl ketones with a p-methoxyacetophenone moiety as a built-in triplet sensitizer (1 and 2, respectively) was compared. When irradiated, ketone 1 produces its cis-isomer, whereas ketone 2 does not yield any photoproducts. Laser flash photolysis of ketone 1 yields a transient spectrum with λmax ∼ 400 nm (τ ∼ 125 ns). This transient is assigned to the first triplet excited state (T1) of 1, which presumably decays to form a triplet biradical (1BR) that is shorter lived than the triplet ketone. In comparison, laser flash photolysis of 2 reveals two transients (τ ∼ 20 and 440 ns), which are assigned to T1 of 2 and triplet biradical 2BR, respectively. Density functional theory calculations support the characterization of the triplet excited states and the biradical intermediates formed upon irradiation of ketones 1 and 2 and allow a comparison of the physical properties of the biradical intermediates. As the biradical centers in 2BR are stabilized by conjugation, 2BR is more rigid than 1BR. Therefore, the longer lifetime of 2BR can be attributed to less-efficient intersystem crossing to the ground state.

Efficient Fusion at Neutral pH by Human Immunodeficiency Virus gp41 Trimers Containing the Fusion Peptide and Transmembrane Domains.

Human immunodeficiency virus (HIV) is membrane-enveloped, and an initial infection step is joining/fusion of viral and cell membranes. This step is catalyzed by gp41, which is a single-pass integral viral membrane protein. The protein contains an ∼170-residue ectodomain located outside the virus that is important for fusion and includes the fusion peptide (FP), N-helix, loop, C-helix, and viral membrane-proximal external region (MPER). The virion initially has noncovalent complexes between three gp41 ectodomains and three gp120 proteins. A gp120 contains ∼500 residues and functions to identify target T-cells and macrophages via binding to specific protein receptors of the target cell membrane. gp120 moves away from the gp41 ectodomain, and the ectodomain is thought to bind to the target cell membrane and mediate membrane fusion. The secondary and tertiary structures of the ectodomain are different in the initial complex with gp120 and the final state without gp120. There is not yet imaging of gp41 during fusion, so the temporal relationship between the gp41 and membrane structures is not known. This study describes biophysical and functional characterization of large gp41 constructs that include the ectodomain and transmembrane domain (TM). Significant fusion is observed of both neutral and anionic vesicles at neutral pH, which reflects the expected conditions of HIV/cell fusion. Fusion is enhanced by the FP, which in HIV/cell fusion likely contacts the host membrane, and the MPER and TM, which respectively interfacially contact and traverse the HIV membrane. Initial contact with vesicles is made by protein trimers that are in a native oligomeric state that reflects the initial complex with gp120 and also is commonly observed for the ectodomain without gp120. Circular dichroism data support helical structure for the N-helix, C-helix, and MPER and nonhelical structure for the FP and loop. Distributions of monomer, trimer, and hexamer states are observed by size-exclusion chromatography (SEC), with dependences on solubilizing detergent and construct. These SEC and other data are integrated into a refined working model of HIV/cell fusion that includes dissociation of the ectodomain into gp41 monomers followed by folding into hairpins that appose the two membranes, and subsequent fusion catalysis by trimers and hexamers of hairpins. The monomer and oligomer gp41 states may therefore satisfy dual requirements for HIV entry of membrane apposition and fusion.

Diagnostic challenges and case management of the first imported case of Plasmodium knowlesi in Sri Lanka.

BACKGROUND: Sri Lanka has achieved 'malaria-free' status and is now in the phase of prevention of re-introduction of malaria. Imported malaria remains a challenge to resurgence of the disease. The diagnostic challenges encountered and the rapid response initiated to manage a Plasmodium infection, which was later confirmed as Plasmodium knowlesi, the first reported case from Sri Lanka, is discussed. CASE PRESENTATION: An army officer who returned from Malaysia in October 2016 was found to be positive for Plasmodium both by microscopy and rapid diagnostic test (RDT) by the Anti Malaria Campaign Sri Lanka (AMC) during his third visit to a health care provider. Microscopy findings were suspicious of P. knowlesi infection as the smears showed parasite stages similar to both Plasmodium malariae and Plasmodium falciparum. Nested PCR at AMC confirmed Plasmodium genus, but not the species. In the absence of species confirmation, the patient was treated as a case of P. falciparum. The presence of P. knowlesi was later confirmed by a semi-nested PCR assay performed at the Environmental Health Institute, National Environmental Agency in Singapore. The parasite strain was also characterized by sequencing the circumsporozoite gene. Extensive case investigation including parasitological and entomological surveillance was carried out. CONCLUSIONS: Plasmodium knowlesi should be suspected in patients returning from countries in the South Asian region where the parasite is prevalent and when blood smear results are inconclusive.

Incidence of inflammatory bowel disease in Gampaha district: details of the Sri Lankan component of the Asia-Pacific Crohn's and colitis epidemiology study.

The aim of this report is to provide details of the methodology and results of the Sri Lankan component of the Asia-Pacific Crohn's and Colitis Epidemiology Study. Fourteen state and private hospitals with specialist services in the Gampaha and Colombo districts were kept under surveillance over a 12 month period to recruit patients with newly diagnosed Inflammatory Bowel Disease (IBD) who were permanent residents of the Gampaha district. Thirty five cases (ulcerative colitis-21, Crohn's disease-13, IBD-undetermined-1) were detected, giving a crude annual IBD incidence of 1.59 per 100,000 population.

Incidence and risk factors of falls among the elderly in the District of Colombo.

OBJECTIVES: To assess the incidence and risk factors of falls among the elderly in the District of Colombo. METHODS: Incidence of falls was assessed by a community based descriptive study with prospective follow up. Risk factors for falls were assessed by a nested case control study. Participants above 65 years residing in 40 Grama Niladhari Divisions in the Colombo district (n=1200) were assessed for falls and followed up for four months. Those who had falls were selected as cases (n=151), while two controls per case were selected from others. MEASUREMENTS: Tests for gait problems, disability, cognitive impairment and vision. RESULTS: The incidence rate of falls was 492 per 1000 person years (95% CI 448-536). Risk factors for falls identified in the multivariate analysis were falls in the previous year (OR 4.67), high disability level (OR 2.04) and high house risk level (OR 1.68). CONCLUSIONS: The high incidence of falls among the elderly reported in this study and the preventable risk factors identify / indicate the necessity and feasibility of their prevention.

Triplet-sensitized photoreactivity of a geminal diazidoalkane.

Photolysis of 1 in chloroform yielded 2 as the major product and a small quantity of 3. Laser flash photolysis demonstrated that upon irradiation, the first excited triplet state of the ketone (T(1K)) of 1 is formed and decayed to form radical 4, which has a λ(max) at 380 nm (τ = 2 µs). Radical 4 expelled a nitrogen molecule to yield imine radical 5 (λ(max) at 300 nm). Density functional theory (DFT) calculations showed that the transition state barrier for the formation of 5 is approximately 4 kcal/mol. In comparison, photolysis of 1 in argon matrices resulted in triplet nitrene 6, which was further characterized with (15)N and D isotope labeling and DFT calculations. Prolonged irradiation of 6 yields triplet imine nitrene 7.

An active metasurface for field-localizing wireless power transfer using dynamically reconfigurable cavities.

Wireless power transfer (WPT) provides a convenient method of delivering energy to multiple devices. With the increasing use of WPT, safety concerns inevitably create the need for a reliable control mechanism. Previous approaches in advanced WPT or metamaterial-enhanced WPT, however, have the limitation that neither the intensity nor the shape of the field-localizing area can be dynamically controlled. To address this limitation, we introduce the novel concept of a hotspot or power-focused region using field-localizing WPT. Using the proposed method, we provide experimental evidence demonstrating that the location, shape, and intensity of the hotspot can be manipulated as desired. The hotspot effectively enhances power delivery to the intended device while reducing leakage to unwanted areas. To dynamically reconfigure the hotspots, we propose an active metasurface with multi-functionality due to its frequency switching and tuning capability. The dynamic reconfiguring capability provides a wide range of versatile practical applications, overcoming the limitations associated with passive metamaterials. Because the location, shape, and intensity of hotspots can readily be controlled, the proposed method is not limited to WPT applications. It can also be used for a broad range of applications that require precise control of power delivery.

Cardiogenic Shock due to Kounis Syndrome following Cobra Bite.

Kounis syndrome is associated with mast cell activation resulting in acute coronary syndrome secondary to an allergic insult. Various drugs such as antibiotics, analgesics, and environmental exposures such as bee, wasp sting, and poison ivy are known to induce Kounis syndrome. A 68-year-old man admitted with a cobra bite on both hands to emergency care unit and sustained cardiorespiratory arrest. Electrocardiogram, taken 6 hours after the cardiac arrest, showed ST elevations in leads V2 to V5 suggestive of anterior ST elevation myocardial Infarction (STEMI). Serum Troponin was 10 ng/ml (control= <0.5). Serum IgE levels were significantly high (19155IU/ml, baseline 100). 2-Dimensional echocardiogram showed anterior and apical-septal hypokinesia with left ventricular ejection fraction of 30-35%. Coronary angiogram was normal. He remained hypotensive requiring inotropic and vasopressor support during ICU stay. This was a case of Kounis syndrome leading to cardiogenic shock secondary to Cobra (naja naja) bite. This is the only reported case of cobra bite causing Kounis syndrome and cardiogenic shock. Identification of the cause of myocardial infarction in snake envenomation is useful in the management as some of the drugs like adrenaline, morphine, and beta blockers may worsen the clinical syndrome if it is due to Kounis syndrome.

Gluconeogenesis from glycerol by ketotic sheep pregnant with twins.

The concentrations of glycerol and glucose in plasma, the entry rates of glycerol and glucose into the plasma pool and the production of glucose from glycerol were measured in four normal sheep pregnant with twins and in the same sheep after the induction of ketosis and after the oral administration of 3 ml/kg body-weight of glycerol in two doses six hours apart. After starvation there was a significant fall in the concentration of glucose and a rise in that of ketone bodies in the plasma. The rise in the concentration of glycerol was not significant. The divided oral dose of glycerol was followed by significant increases in the concentrations of glycerol and glucose and a significant fall in that of ketone bodies in plasma. After starvation, glucose and glycerol entry rates fell significantly from 42.0 +/- 3.5 to 18.1 +/- 1.4 mmol per hour and from 28.1 +/- 4.6 to 13.5 +/- 2.9 mmol per hour respectively. The amount of glucose formed from glycerol decreased from 5.4 +/- 1.2 to 3.0 +/- 0.5 mmol per hour. After a divided oral dose of glycerol, glycerol entry in the ketotic sheep rose significantly from 13.5 +/- 2.9 to 320 +/- 24.1 mmol per hour and glucose entry rate rose significantly from 18.1 +/- 1.4 to 71.5 +/- 10.1 mmol per hour. The amount of glucose produced from glycerol increased from 3.0 +/- 0.5 to 62.1 +/- 9.2 mmol per hour after the administration of glycerol. The oral dose of glycerol had no obvious effect on the clinical signs of induced ketosis.

The utilisation of glycerol by sheep.

Increased but steady concentrations of glycerol and glucose in carotid, jugular and portal plasma of sheep were obtained between 2.5 and 3.5 h after the second of two oral doses of glycerol (2 and a ml/kg body weight with a 6 h interval between) and the concentration of glycerol in portal plasma was greater than in the other vessels. During the last hour of a 3.5 h continuous infusion of [14C]glycerol and [3H]glucose, ie, between 2.5 and 3.5 h after the second dose of glycerol, specific radioactivity(SRA) of glycerol and of [14C] an [3H] glucose were measured in plasma obtained from the three previously mentioned sites in dosed and undosed sheep. Although in dosed sheep the SRA of glycerol in portal plasma was lower than that in jugular plasma, the difference was such that the SRA in jugular plasma could be used to calculate entry rates and the rate of production of glucose from glycerol. Mean (+/- SE) glycerol entry rate in four fed sheep increased from 9.2 +/- 1.2 to 62.7 +/- 0.9 mg C/min after a divided oral dose of glycerol. Mean glucose entry rate increased from 29.0 +/0 3.4 to 58.3 +/- 7.6 mg C/min. The amount of glucose which was derived from glycerol increased from 5.4 +/- 1.6 to 35.5 +/- 3.7 mg C/min. This increase accounted for the increase in total glucose entry.

The effect of triamcinolone acetonide on plasma glucose and ketone concentration and on the total entry rate of glucose in twin pregnant hypoglycaemic ketotic sheep.

Hypoglycaemic ketosis clinically resembling pregnancy toxaemia was induced by starvation in Clun Forest sheep pregnant with twins. Total glucose entry was measured by the continuous infusion of trace amounts of (2-3H) glucose before and after the induction of ketosis and 24 h after the intramuscular injection of the ketotic sheep with triamcinolone acetonide (0.5 mg/kg). The concentration of glucose in plasma fell significantly after the induction of ketosis and rose significantly after the injection of steroid. The total entry rate of glucose fell significantly after the induction of ketosis and rose, but no significantly, after steroid injection. It is suggested that the dose of steroid which was used may inhibit glucose utilisation by peripheral tissues. The induction of ketosis significantly reduced the duration of pregnancy but the steroid injection did not produce a significant additional effect.

Epidemiology of chronic kidney disease in a Sri Lankan population.

CONTEXT: Chronic kidney disease (CKD) is characterized by progressive destruction of renal mass with irreversible sclerosis and loss of nephrons over a period of months to years, depending on the underlying etiology. AIM: To describe demographic patterns and identify common causes of CKD in patients admitted to ward 41 and 48B, National Hospital of Sri Lanka. SETTINGS AND DESIGN: A hospital based descriptive 3-month study was conducted at ward 41 and 48B, National Hospital of Sri Lanka. A case record form was used to record sociodemographic variables, stage of renal disease, and etiology of patients in established chronic renal failure. Sources of data included patient interviews, diagnosis cards and case records, ultrasound scan reports, and biopsy findings. RESULTS: One hundred and twenty-one patients were recruited with male to female ratio being 2.5:1 (86:35). Mean age of the population was 47.8 years (SD +/- 13.7). Common causes of CKD identified in these patients included diabetic nephropathy (37, 30.6%), hypertension (16, 13.2%), glomerulonephritis (12, 9.9%), and obstructive uropathy (10, 8.3%). The cause was unknown in 25.6% of patients with chronic renal disease. Fifty percent of patients were from the Western Province. The leading cause of CKD in patients from the Western Province was diabetic nephropathy (26, 37.7%). The etiology of CKD was unknown in majority of the patients (14, 27.4%) from other provinces. The difference in incidence of diabetic nephropathy in the Western Province as to other provinces was not statistically significant (P > 0.05). CONCLUSION: Diabetes is a major contributor to CKD reflecting changing disease epidemiology in Sri Lanka.