Ring opening polymerization of lactides and lactones by multimetallic alkyl zinc complexes derived from the acids Ph₂C(X)CO₂2H (X = OH, NH₂ )

The reaction of the dialkylzinc reagents R₂Zn with the acids 2,2-Ph₂C(X)(CO₂H), where X = NH₂, OH, i.e. 2,2′-diphenylglycine (dpgH) or benzilic acid (benzH2), in toluene at reflux temperature afforded the tetra-nuclear ring complexes [RZn(dpg)]₄, where R = Me (1), Et (2), 2-CF₃C₆H₄ (3), and 2,4,6-F₃C₆H₂ (4); complex 2 has been previously reported. The crystal structures of 1·(2MeCN), 3 and 4·(4(C₇H₈)·1.59(H₂O)) are reported, along with that of the intermediate compound (2-CF₃C₆H₄)3B·MeCN and the known compound [ZnCl₂(NCMe)₂]. Complexes 1–4, together with the known complex [(ZnEt)₃(ZnL)₃(benz)₃] (5; L = MeCN), have been screened, in the absence of benzyl alcohol, for their potential to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and rac-lactide (rac-LA); the co-polymerization of ε-CL with rac-LA was also studied. Complexes 3 and 4 bearing fluorinated aryls at zinc were found to afford the highest activities

Immunohistochemical Expression of Epidermal Growth Factor Receptor in Human colorectal Adenocarcinoma (A clinicopathological study)

Background: Colorectal Adenocarcinoma contributes one of the most common malignancies and the second leading cause of death from cancer in the western world. Epidermal growth factor receptor (EGFR) belongs to a family (ErbB-tyrosine receptors), EGFR plays an important role in the pathogenesis of colorectal cancer. Objectives: to evaluate the immunohistochemical expression of epidermal growth factor receptors (EGFR) in colorectal adenocarcinoma and to correlate this expression with different clinicopathological parameters. Pateints and method: In this study clinicopathological parameters of twenty five colorectal adenocarcinoma cases diagnosed in private pathology laboratories in Baghdad /Iraq from November 2012 to September 2013 were respectively evaluated in terms of age, gender, pathological diagnosis including; tumor location, lymph node status. EGFR expression was investigated immunohistochemically. Results: twenty five colorectal cancer patients were included in this study with median age 54.5, range from (28-81)years, 15 cases (60%) were female and 10 (40%) cases were male. Tumor size range from 3-10 cm with mean 6.5 cm, 10 (40%) cases were from rectum, 7 (28%) from the right side colon & 8 (32%) cases were from from left side colon. Twenty three (92%) cases were moderately differentiated, and two (8%) cases were poorly differentiated, five (20%) cases were T1, 10 (40%) cases were T2, 5 (20%) cases were each T3 & T4 respectively. 3 (12%) cases were N1, 7 (28%) cases were N2, and fifteen (60%) cases have no lymph node involvement. Three (12%) cases with distant metastasis. Eighteen (72%) cases of colorectal adenocarcinoma demonstrate EGFR reactivity in > 1% of the tumor cells. No significant statistical correlation was noticed between EGFR expression and each of age, gender, site of the tumor and grade of tumor (P value > 0.05). A significant statistical correlation was noted between EGFR expression and local tumor invasion (T) and lymph node involvement (p value <0.05). Conclusion: Epidermal growth factor receptor plays an important role in colorectal adenocarcinoma oncogenesis. EGFR expression appears to have a value as a prognostic biomarker, since it’s expression by the tumor cells is significantly correlated to lymph node involvement and tumor local invasion

Enhanced probability density function using APD in SAC-OCDMA systems based SPD technique

This paper examines the avalanche photodiode (APD) gain impact on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems based single photodiode detection (SPD) technique. Numerical results are used for inspecting the APD gain influence upon the probability density function (PDF) and signal-to-noise ratio (SNR) performance. The usage of APD over positive-intrinsic-negative (PIN) photodiode accommodates more users with improved PDF and higher SNR

Triple-play services using different detection techniques for SAC-OCDMA systems

The development of many high bit-rate multimedia applications has emphasized the demand for service differentiation or prioritization techniques to ensure end-user quality-of-service (QoS) necessities. This paper focuses on utilizing different detection schemes in spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems to support 'triple-play' services (voice, video, and data) with diverse QoS requirements. The used subtraction detection techniques are complementary, AND, as well as modified-AND.Modified double-weight (MDW) codes are used as the signature codes for SAC-OCDMA systems.The simulation results show that modified-AND subtraction detection demonstrates better performance over other detection approaches

APD Gain Effect on SAC-OCDMA System using Modified-AND Detection Technique

This paper investigates the avalanche photodiode (APD) gain effect on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a modified-AND subtraction detection in comparison to the conventional AND detection scheme. Analytical results are presented to investigate the APD gain impact on the bit-error rate (BER) performance. In addition, we confirm the influence of the APD over the positive-intrinsic-negative (PIN) photodiode on the system performance using data transmission simulations

Reducing BER of spectral-amplitude coding optical code-division multiple-access systems by single photodiode detection technique

In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4x10^-28 for SPD technique is much better compared to 9.3x10^-6 and 9.6x10^-3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations