9 resultados para double-dark resonances
em Brock University, Canada
Resumo:
Therllloelynalllics of lllodel 11lel1ll)rane systeills containing 1110nollnsaturatecl I)lloSI)holil) ids is strongly infllienced l)y the I)osition of the C==C dOlll)le })ond in tIle acyl chain. The telllI)eratllres of both chain-nlelting (TM) and La -+ HI! (TH) I)hase traIlsitions are lowered by IIp to 20°C when C==C is Inoved froln positions 6 or 11 to I)osition 9 in an 18-carl)on chain. This work is an attellll)t to ellicidate the uIlderlying Illoleclilar Illechanisllls reSI)Onsi])le for tllese draillatic tllerillodynaillic changes. Mixtllres of di-18: 1 l)hoSI)hatidylethanolanline with C==C at l)ositioIlS 6, 9, 11 were llsed, witll a sI1lall aI1lOlint of I)erdellterated tetradecanol, known to })e a gooel rel)Orter of the cllain Illoleclilar order. SI)ectral second 11I0I1lents were llsed to Illonitor tIle La -+ HII I)hase transition, which was fOllnd to ])e ])road (2-6°C), with a slight llysteresis on heatiIlg/cooling. The orientational order I)rofiles were nleasllred 1lSiIlg 2H Illiclear Illagnetic resonance and changes in these order I)rofiles between La aIld HII I)hases silow l)oth a local increase in order in the vicinity of the C==C bonds and an o\Terall decrease ill the average orientational order of the chain as a whole. These Sll])tle changes recluire })oth high-fidelity SI)ectrosCol)y and a careflll data analysis that takes into aCCOllnt the effects due to l)artiall1lagnetically-indllced orientational ordering of the l)ilayers. In tIle COIltext of SOllle recently rel)Orted cross-relaxation 11leaSlirenlents in Silllilar l)llOSI)llolil)iels, 0111' reslilts sllggest that large-anll)litllde conforlllational changes in the interior of tIle I110del 111eI11])ranes I)lay a 1110re significant role than I)reviollsly thOllght.
Resumo:
Genetic chimeras made by aggregating early mouse embryos have many uses in developmental biology and have also provided insights into embryonic growth regulation. There is an indication that the embryo can regulate for an increase in size because although aggregation chimeras are twice as big as normal embryos when made, they are born of normal size. Upward regula..... tion of size reduced embryos is also possible. Half embryos made by the isolation or destruction of one of the blastomeres of a 2-cell embryo are also born of normal size. Little is known about the timing or the mechanism of this size regulation. In this study, the timing of size regulation in double and half embryos was clearly established by comparison of cell numbers derived from serial reconstruction of light microscope sections of control and experimental embryos. It was shown that size regulation in double embryos occurred around 6dl6h and in half embryos by 7dOh. Size regulation occurred in all tissues at the same time indicating a single control mechanism for the entire embryo. More detailed examination of the growth of double embryos revealed that size regulation occurred by alteration in cell cycle length~ No excessive cell death was found in double embryos compared to the controls and continuous labelling with [3H] thymidine showed no large non-dividing cell population in double embryos. However, a comparison of the mitotic index of double and control embryos after colcemid treatment, revealed a large difference between the two around 5dl6h to 6d16h. During this period, control embryos underwent a proliferative burst not shown by the double embryos. The mechanism for cell cycle control is not clear; it may be intrinsic to the embryo or determined by the uterine environment. Evidence was found suggesting that differentiation in the postimplantation embryo was cell number dependent. The timing of differentiative events was examined in half, double and control embryos. Proamnion formation, which occurs prior to size regulation, occurs at the same cell number but at different times in the three groups of embryos. However mesoderm which appears after size regulation was seen at the same time in all grollps of embryos.
Resumo:
The present work presents two studies that examined the association of perfectionism, operationally defined by Hewi t t and Fl e t t ' s (1991) multidimensional mode l of perfectionism, with health and subjective well-being (SWB). The underlying question of this research was whether perfectionism could be beneficial as well as detrimental to health and well-being, as this is one of the mos t highly debated questions in the current literature. In samples of relatively healthy university students (n = 538) and community adults suffering from various chronic illnesses (n = 772), results from Study One indicated that socially prescribed perfectionism (SPP) is directly associated wi th poor e r he a l th and well-being. Results further showed f rom a personcentered perspective that there is a l a rge group of individuals wi th high levels of SPP and that i t is indeed these individuals who reported the poorest health and lowe s t levels of well-being. Other-oriented perfectionism was found to be unrelated to health and SWB. Findings revealed that when perfectionism is self-imposed (i.e., self-oriented perfectionism; SOP), i t is neither healthy nor unhealthy in an absolute sense. From the variable-centered perspective, this conclusion was supported by the f a c t tha t SOP was associated wi th both positive (e.g., be t t e r mental health and highe r levels of SWB in the student sample), and nega t ive correlates (e.g., higher levels of negative affect, stress, and neuroticism in both samples). Evidence f rom the chronically-ill sample further substantiated this conclusion by showing that there may be an optimal level of SOP, because mode r a t e levels of SOP we r e found to be associated with be t t e r health and highe r levels of SWB, whereas levels tha t we r e too low or too high we r e found to be associated with poor e r health and lowe r levels of SWB. Findings f rom the person-centered approach we r e particularly informative, in that they not only demonstrated tha t unique profiles of
Resumo:
This thesis describes the chemoenzymatic synthesis of three morphine alkaloids. The total synthesis of dihydrocodeine and hydrocodone was accomplished starting from bromobenzene in 16 and 17 steps, respectively. The key steps included a microbial oxidation of bromobenzene by E. coli JM109 (pDTG601A), a Kazmaier-Claisen rearrangement of glycinate ester to generate C-9 and C-14 stereo centers, a Johnson-Claisen rearrangement to set the C-13 quaternary center, and a C-10/C-11 ring closure via a Friedel-Crafts reaction. In addition, the total synthesis of ent-hydromorphone starting from β-bromoethylbenzene in 12 steps is also described. The key reactions included the enzymatic dihydroxylation of β-bromoethylbenzene to the corresponding cis-cyclohexadienediol, a Mitsunobu reaction, and an oxidative dearomatization followed by an intramolecular [4+2] cycloaddition.
Resumo:
The article was published in the journal Meat Science, Vol. 46, No.4. The focus is data collected for cattle temperament and the quality of meat produced.
Resumo:
The summary of the article reads "A new double rail conveyor restrainer for handling cattle at the slaughter plant is described. It has improved safety and ergonomics compared to the V restrainer conveyor it replaces. Cattle ride astride a moving conveyor. This design could also be adapted for veterinary work."
Resumo:
Examination of Henry Nelles (2 double-sided pages, handwritten). The pages are stained and contain some holes. This affects some of the text. [These are copies of the answers from the previous document], 1830.
Resumo:
Questions and answers of W. Henry Griffen (2 double-sided pages, handwritten). These pages are stained and slightly torn. This affects a small portion of the text, 1830.
Resumo:
Questions put to Edwards [illegible] (2 double-sided pages, handwritten).These pages are stained and slightly torn. This affects a small portion of the text, 1830.