SPECTROSCOPIC CHARACTERIZATION OF LANTHANUM-MEDIATED HYDROCARBON ACTIVATION

Lanthanum (La)-promoted hydrocarbon activation reactions were carried out in a laser vaporization metal cluster beam source. Reaction products were identified by time-of-flight mass spectrometry, and the approximate ionization thresholds of La-hydrocarbon complexes were located with photoionization efficiency spectroscopy. The accurate ionization energies and vibrational frequencies of the La complexes were measured using mass analyzed threshold ionization (MATI) spectroscopy. Their molecular structures and electronic states were investigated by combing the MATI spectroscopic measurements with quantum chemical and Franck-Condon factor calculations. In this dissertation, La-mediated C-H and C-C bond activation reactions were investigated for several small alkynes (acetylene, propyne) and alkenes (propene, 1,3-butadiene, 1-butene). The C-H bond activation was observed for both alkynes and alkenes and the C-C bond activation for alkenes. The metal-hydrocarbon intermediates formed by the C-H or C-C bond cleavage reacted further with one or more parent hydrocarbon molecules to produce larger species by C-C bond coupling reactions. Structural isomers of the intermediates and products were identified within an energy range of several kilocalories per mole. Reaction pathways for the intermediate and product formations were studied by theoretical calculations. The ground electron configuration of La atom is 4d16s2.Upon the hydrocarbon coordination, La atom is excited to a 4d26s1 configuration to facilitate the formation of two La-C bonds. After the metal-hydrocarbon complex formation, only one electron is left in the 6s orbital of the metal center. Therefore, the most stable electronic state of the La complexes studied in this work is in a doublet spin state. Ionization of the doublet state yields a preferred singlet ion state. Although La is in the formal oxidation state of +2, the ionization energies of the metal-complexes are significantly lower than that of the free atom. This observation suggests that the concept of the formal oxidation state widely used in chemistry textbooks is not useful in predicting the change of the ionization energy of a metal atom upon ligation. Moreover, ionization has a very small effect on the geometry of the hydrocarbon fragment in each complex but significantly reduces the La-C distances as a result of an additional charge interaction

Lanthanum-Mediated Dehydrogenation of 1- and 2-Butynes: Spectroscopy and Formation of La(C\u3csub\u3e4\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e) Isomers

La atom reactions with 1-butyne and 2-butyne are carried out in a laser-vaporization molecular beam source. Both reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butynes. The dehydrogenated species La(C4H4) is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of La(C4H4) produced from the two reactions exhibit two identical transitions, each consisting of a strong origin band and several vibrational intervals. The two transitions are assigned to the ionization of two isomers: La(η4–CH2CCCH2) (Iso A) and La(η4–CH2CHCCH) (Iso B). The ground electronic states are 2A1 (C2v) for Iso A and 2A (C1) for Iso B. The ionization of the doublet state of each isomer removes a La 6s-based electron and results in a 1A1 ion of Iso A and a 1A ion of Iso B. The formation of Iso A from 2-butyne and Iso B from 1-butyne involves the addition of La to the C≡C triple bond, the activation of two C(sp3)–H bonds, and concerted elimination of a H2 molecule. The formation of Iso A from 1-butyne and Iso B from 2-butyne involves the isomerization of the two butynes to 1,2-butadiene in addition to the concerted H2 elimination

Topology based packet marking for IP traceback

IP source address spoofing exploits a fundamental weakness in the Internet Protocol. It is exploited in many types of network-based attacks such as session hijacking and Denial of Service (DoS). Ingress and egress filtering is aimed at preventing IP spoofing. Techniques such as History based filtering are being used during DoS attacks to filter out attack packets. Packet marking techniques are being used to trace IP packets to a point that is close as possible to their actual source. Present IP spoofing&nbsp; countermeasures are hindered by compatibility issues between IPv4 and IPv6, implementation issues and their effectiveness under different types of attacks. We propose a topology based packet marking method that builds on the flexibility of packet marking as an IP trace back method while overcoming most of the shortcomings of present packet marking techniques.<br /

Mass-Analyzed Threshold Ionization Spectroscopy of Lanthanum-Hydrocarbon Radicals Formed by C—H Bond Activation of Propene

La(C3H4) and La(C3H6) are observed from the reaction of laser-vaporized La atoms with propene by photoionization time-of-flight mass spectrometry and characterized by mass-analyzed threshold ionization spectroscopy. Two isomers of La(C3H4) are identified as methyl-lanthanacyclopropene [La(CHCCH3)] (Cs) and lanthanacyclobutene [La(CHCHCH2)] (C1); La(C3H6) is determined to be H—La(η3-allyl) (Cs), a C—H bond inserted species. All three metal-hydrocarbon radicals prefer a doublet ground state with a La 6s-based electron configuration. Ionization of the neutral doublet state of each of these radicals produces a singlet ion state by removing the La-based 6s electron. The threshold ionization allows accurate measurements of the adiabatic ionization energy of the neutral doublet state and metal-ligand and ligand-based vibrational frequencies of the neutral and ionic states. The formation of the three radicals is investigated by density functional theory computations. The inserted species is formed by La inserting into an allylic C—H bond and lanthanacyclopropene by concerted vinylic H2 elimination, whereas lanthanacyclobutene involves both allylic and vinylic dehydrogenations. The inserted species is identified as an intermediate for the formation of lanthanacyclobutene

Glucagon receptor antagonist and GIP agonist combination for diet induced obese mice.

Ablation of glucagon receptor signaling represents a potential treatment option for type 2 diabetes (T2DM). Additionally, activation of glucose-dependent insulinotropic polypeptide (GIP) receptor signaling also holds therapeutic promise for T2DM. Therefore, this study examined both independent and combined metabolic actions of desHis1Pro4Glu9(Lys12PAL)-glucagon (glucagon receptor antagonist) andd-Ala2GIP (GIP receptor agonist) in diet-induced obese mice. Glucagon receptor binding has been linked to alpha-helical structure and desHis1Pro4Glu9(Lys12PAL)-glucagon displayed enhanced alpha-helical content compared with native glucagon. In clonal pancreatic BRIN-BD11 beta-cells, desHis1Pro4Glu9(Lys12PAL)-glucagon was devoid of any insulinotropic or cAMP-generating actions, and did not impeded-Ala2GIP-mediated (P&lt;0.01 toP&lt;0.001) effects on insulin and cAMP production. Twice-daily injection of desHis1Pro4Glu9(Lys12PAL)-glucagon ord-Ala2GIP alone, and in combination, in high-fat-fed mice failed to affect body weight or energy intake. Circulating blood glucose levels were significantly (P&lt;0.05 toP&lt;0.01) decreased by all treatments regimens, with plasma and pancreatic insulin elevated (P&lt;0.05 toP&lt;0.001) in all mice receivingd-Ala2GIP. Interestingly, plasma glucagon concentrations were decreased (P&lt;0.05) by sustained glucagon inhibition (day 28), but increased (P&lt;0.05) byd-Ala2GIP therapy, with a combined treatment resulting in glucagon concentration similar to saline controls. All treatments improved (P&lt;0.01) intraperitoneal and oral glucose tolerance, and peripheral insulin sensitivity.d-Ala2GIP-treated mice showed increased glucose-induced insulin secretion in response to intraperitoneal and oral glucose. Metabolic rate and ambulatory locomotor activity were increased (P&lt;0.05 toP&lt;0.001) in all desHis1Pro4Glu9(Lys12PAL)-glucagon-treated mice. These studies highlight the potential of glucagon receptor inhibition alone, and in combination with GIP receptor activation, for T2DM treatment.</jats:p

EFFECT OF DIAMETER ON VOLUME MEASUREMENTS OF Pinus caribaea (MORELET).

is the most important parameter in commercial forestry especially at themature stage. Among those methods, the most common way is to useSmalian's, Huber's and Newton's formulae. In order to use these threeformulae the stem should be divided into sections and volume of each sectionshould be determined separately. Huber's formula is the easiest one to usebecause it needs only one diameter measurement of the log. Smalian'sformula needs two diameter measurements while Newton's formula needsthree. Log length is required for all three formulae. Due to the low number ofmeasurements Huber's formula is more popular among the foresters.However, Smalian's and Huber's formulae can introduce errors because theyuse fewer measurements compared to the Newton's formula. Therefore thepresent study was conducted to identify the variation of the error withincreasing diameter of trees when Huber's and Smalian' s formulae are used.Newton's formula was considered as the one that provides precise values involume estimation.Present study was conducted in the 26 year old Pinus caribaea plantation inYagirala Forest Reserve situated in the low country wet zone of Sri Lanka. Inorder to represent the whole area of the forest, stratified random samplingmethod was used and one O.OSha sample plot was laid in each stratum (i.e.,valley, slope and ridge).Each tree of the plot was divided into twelve 1m long sections using aranging staff. Bottom, mid and top diameter of the each section wasmeasured using the Spiegal relascope. Other than above measurements,diameter at the breast height and height of the tree were measured using thediameter tape and the Blume Leiss Altimeter respectively.In order to find out whether the diameter at breast height affected on volumecalculations using above formulae, trees were grouped into two centimeterdiameter classes. At each diameter class, volumes estimated using Huber'sformula were tested separately for different section lengths using one wayANa vA. Results indicated that at 95% probability level diameter does not have a significant influence in volume measurements for Huber's formula upto twelve meter stem length.First part of this study was conducted to identify the effect of Huber's andSmalian's formula in volume calculations without considering the diameterdifferences of trees in the forest and results proved that Huber's formulaproduced least errors when compared with Smalian's formula. However, inthis instance the maximum stem length that can be measured using Huber'sformula became 6m. According to both tests, it can be concluded thatHuber's formula can be use effectively up to 6m stem length in volumecalculations with out considering the diameter range of trees

Spectroscopy and Formation of Lanthanum-Hydrocarbon Radicals Formed by C—C Bond Cleavage and Coupling of Propene

La reaction with propene is carried out in a laser-vaporization molecular beam source. Three La-hydrocarbon radicals are characterized by mass-analyzed threshold ionization (MATI) spectroscopy. One of these radicals is methylenelanthanum [La(CH2)] (Cs), a Schrock-type metal carbene. The other two are a five-membered 1-lanthanacyclopent-3-en [La(CH2CHCHCH2)] (Cs) and a tetrahedron-like trimethylenemethanelanthanum [La(C(CH2)3)] (C3v). Adiabatic ionization energies and metal-ligand stretching and hydrocarbon-based bending frequencies of these species are measured from the MATI spectra, preferred structures and electronic states are identified by comparing the experimental measurements and spectral simulations, and reaction pathways for the formation of the metal-hydrocarbon radicals are investigated with density functional theory calculations. All three radicals prefer doublet ground electronic states with La 6s1-based valence electron configurations, and singly charged cations favor singlet states generated by the removal of the La 6s1 electron. The metal-carbene radical is formed via multi-step carbon-carbon cleavage involving metallacyclization, β-hydrogen migration, and metal insertion. The metal-carbene radical formed in the primary reaction reacts with a second propene molecule to form the five-membered-ring and tetrahedron-like isomers through distinct carbon-carbon coupling paths

Factors associated with the level of inhibitory control in elderly people living in elderly care institutions in Galle District, Sri Lanka

Objectives: The proportion of elderly people living in institutions has increased in Sri Lanka duringthe recent decades as a result of population aging and ongoing sociocultural changes. Cognitivefunctions that are important for goal directed behavior will be increasingly important for independentliving. Inhibitory control of irrelevant information (IC) is such cognitive process vital for this. Hencethis study was conducted to assess the level of inhibitory control and associated factors among elderlypeople living in elderly care institutions in Galle District.Methods: Study was conducted in 190 elderly people living in institutions who are physicallyindependent with Barthel’s index score of more than 90. IC was assessed via computerized stroopinhibitory task. Number of errors was calculated to assess the level of inhibitory control. Groupdifferences were assessed through independent sample t test and significant level was kept at p<0.05.Results: The sample comprised of 69.5% (n=132) females with a mean age of 71.78 years (+6.5). Meannumber of errors of the stroop tasks was 8.88 (+3.99). The number of errors in the stroop inhibitory taskwas significantly lower among females (n=132, p<0.01) who have had above secondary education(n=33, p<0.05), who engaged in group (n=153, p<0.05) and leisure time activities (n=173, p<0.05) andwho were younger than 70 years of age (n=78, p<0.01).Conclusions: IC was significantly associated with age, educational status, gender, engagement in groupand leisure time activities among the study sample

Systematic review on barriers and enablers for access to diabetic retinopathy screening services in different income settings.

BackgroundDiabetic retinopathy (DR) can lead to visual impairment and blindness if not detected and treated in time. Knowing the barriers/enablers in advance in contrasting different country income settings may accelerate development of a successful DR screening (DRS) program. This would be especially applicable in the low-income settings with the rising prevalence of DR.ObjectivesThe aim of this systematic review is to identify and contrast the barriers/enablers to DRS for different contexts using both consumers i.e., people with diabetes (PwDM) and provider perspectives and system level factors in different country income settings.MethodsWe searched MEDLINE, Embase, CENTRAL in the Cochrane Library from the databases start date to December 2018. We included the studies reported on barriers and enablers to access DRS services based at health care facilities. We categorised and synthesized themes related to the consumers (individuals), providers and the health systems (environment) as main dimensions according to the constructs of social cognitive theory, supported by the quantitative measures i.e., odds ratios as reported by each of the study authors.Main resultsWe included 77 studies primarily describing the barriers and enablers. Most of the studies were from high income settings (72.7, 56/77) and cross sectional in design (76.6, 59/77). From the perspectives of consumers, lack of knowledge, attitude, awareness and motivation were identified as major barriers. The enablers were fear of blindness, proximity of screening facility, experiences of vision loss and being concerned of eye complications. In providers’ perspectives, lack of skilled human resources, training programs, infrastructure of retinal imaging and cost of services were the main barriers. Higher odds of uptake of DRS services was observed when PwDM were provided health education (odds ratio (OR) 4.3) and having knowledge on DR (OR range 1.3–19.7).ConclusionKnowing the barriers to access DRS is a pre-requisite in development of a successful screening program. The awareness, knowledge and attitude of the consumers, availability of skilled human resources and infrastructure emerged as the major barriers to access to DRS in any income setting