Disruption of thin- and thick-wall microalgae using high pressure gases: Effects of gas species, pressure and treatment duration on the extraction of proteins and carotenoids.

Industrial scale microalgal cell disruption requires low cost, high efficiency and structural conservation of biomolecules for biorefinery. Many cultivated microalgae have thick walls and these walls are barriers for efficient cell disruption. Until recently, despite the high biodiversity of microalgae, little attention has been paid to thin-wall microalgal species in the natural environment for the production and recovery of valuable biomolecules. Instead of developing high power cell disruption devices, utilization of thin-wall species would be a better approach. The present paper describes a simple device that was assembled to evaluate the viability and effectiveness of biomolecule extraction from both thin- and thick-wall species as a proof of concept. This device was tested with high-pressure gases including N2, CO2 plus N2, and air as the disruption force. The highest nitrogen pressure, 110 bar, was not able to disrupt the thick-wall microalgal cells. On the other hand, the thin-wall species was disrupted to different degrees using different pressures and treatment durations. In the same treatment duration, higher nitrogen pressure gave better cell disruption efficiency than the lower pressure. However, in the same pressure, longer treatment duration did not give better efficiency than the shorter duration. High pressure CO2 treatments resulted in low soluble protein levels in the media. The best conditions to disrupt the thin-wall microalgal cells were 110 bar N2 or air for 1 min among these tests. In these conditions, not only were the disruption efficiencies high, but also the biomolecules were well preserved.

Supercritical fluid extraction of valuable compounds from microalgal biomass.

Many studies have demonstrated that the global demand for renewable biofuels, natural food pigments, and antioxidants has made microalgae a more attractive alternative resource. The application of supercritical fluid extraction (SFE) on the valuable compounds recovery from microalgal biomass has several advantages as compared to the conventional organic solvent extraction methods, especially for environmental considerations. This review presents comprehensive information on the current state of using SFE to recover valuable components from microalgal biomass, such as total lipids, long chain fatty acid and pigments, as well as the utilization and characteristics of the SFE technology. In addition, key factors and challenges that should be addressed during the application of SFE technology are also discussed. This report provides a useful guide that can aid in the future development of more efficient microalgae-based biorefinery process.

Surgical treatment of acute acromioclavicular joint injuries using a modified Weaver-Dunn procedure and clavicular hook plate.

Various surgical procedures have been described for the treatment of complete acromioclavicular joint dislocation, but no consensus exists on the optimal therapy. The aim of each type of procedure is to stabilize the clavicle by substitution of the ruptured coracoclavicular ligaments. Treatment modalities have changed with increasing understanding of the nature of the problem and the biomechanics of the joint. This article presents a method consisting of a modified Weaver-Dunn procedure and a clavicular hook plate for the operative management of acute acromioclavicular joint injuries.We performed a retrospective study of 46 patients who had undergone a modified Weaver-Dunn procedure with a clavicular hook plate for acute acromioclavicular joint injuries between July 2002 and December 2006. Average follow-up was 36.6 months (range, 24-46 months). There was 1 skin-deep infection, 1 dislocation of the hook, and 2 redislocations of the acromioclavicular joint. Thirteen patients had some calcification between the clavicle and the coracoid process, which did not cause loss of motion or other symptoms. All but 1 patient returned to work, and all but 1 returned to their preoperative activity level. The mean Constant score was 88.2 points. The mean Disabilities of the Arm, Shoulder, and Hand (DASH) score was 12.2 points.Treatment of acute acromioclavicular joint injuries using a modified Weaver-Dunn procedure and a clavicular hook plate showed good short-term clinical results with a low complication rate. Further investigation and long-term results are needed to confirm these preliminary findings.

Comparison of plates versus intramedullary nails for fixation of displaced midshaft clavicular fractures.

BACKGROUND: We compare the use of plate and screws versus intramedullary nails in the operative management of patients with displaced midclavicular fractures. METHODS: Between March 2006 and June 2007, we performed a retrospective comparison of a demographically balanced sample of 110 patients (aged 16-65 years) who had received either plates or nails for completely displaced midshaft clavicular fractures. RESULTS: We selected 59 plate-fixed and 51 nail-fixed patients. There was no significant difference between the groups with respect to age, gender, height, dominant arm, fracture angulation, fracture shortening, total fracture displacement, or mechanism of injury. Outcomes were significantly higher in the plate group compared with the nail group for the length of hospital stay (4.6 days ± 2.1 days vs. 5.9 days ± 2.6 days, p = 0.006), operative blood loss (67.5 mL ± 36.2 mL vs. 127.9 mL ± 48.8 mL, p < 0.0001), and size of surgical wound (11.9 cm ± 4.4 cm vs. 22.3 cm ± 4.5 cm, p < 0.0001). There was no significant difference in operative time, time to union, restoration of mobility (forward flexion, abduction, external rotation, and internal rotation), number of nonunions, number of malunions, infection, need for hardware removal, early mechanical failure, time to return to work, and Constant Shoulder and Disabilities of the Arm, Shoulder, and Hand functional scores. CONCLUSION: Our results demonstrate no significant differences in functional outcome and nonunion rates between nails and plates fixation for displaced midshaft clavicular fractures.

Clear evidence of electron delocalization: synthesis, structure, magnetism, EPR and DFT calculation of the asymmetric hexanickel string complex containing a single mixed-valence (Ni(2))(3+) unit.

This paper describes the physical properties of the (Ni(2))(3+) mixed-valence unit that is an excellent conductivity-enhanced tool for metal string complexes.

Asymmetric heterometal string complexes: stereochemical control of the unique isomer of (4,0)[CuCuPd(npa)4Cl][PF6] and (4,0)[CuCuPt(npa)4Cl][PF6].

This paper describes the synthesis and physical properties of a unique metal string complex isomer containing an asymmetric heterometallic backbone.

Abstraction reactions of heavy cyclobutenes with carbon tetrachloride. A theoretical study.

The potential energy surfaces for the abstraction reactions of heavy cyclobutenes with CCl(4) have been characterized in detail by using density functional theory (B3LYP/LANL2DZdp), including zero-point corrections. Seven heavy cyclobutene species including A (C-C-C=C), B (Si-Si-Si=Si), C (Ge-Ge-Ge=Ge), D (Si-Si-Ge=Ge), E (Si-Si-Ge=Sn), F (Sn-Sn-Sn=Sn), and G (Pb-Pb-Pb=Pb) have been chosen in this work as model reactants. All the interactions involve a Cl or CCl(3) shift via a two-center transition state. The activation barriers and enthalpies of the reactions were compared in order to determine the relative heavy cyclobutene reactivity as well as the influence of substituents on the reaction potential energy surface. As a result, our theoretical investigations suggest that a heavy cyclobutene species that contains more massive and less electronegative atoms in the double bond should undergo radical abstraction reactions with CCl(4) more readily than one containing less massive and more electronegative atoms. Moreover, we show that having undergone an initial chlorine atom abstraction, a heavy cyclobutene will then proceed to undergo a second abstraction to give a tetrachloro derivative. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. The results obtained allow us to make several predictions.

The adjunctive effect of a binding peptide on bone morphogenetic protein enhanced bone healing in a rodent model of spinal fusion.

STUDY DESIGN: A prospective 8-week interventional trial employing a rat model of spinal fusion to test the effect on bone morphogenetic protein binding peptide (BBP) on rhBMP-2 induced bone healing. OBJECTIVES: To determine if the addition of BBP to the collagen sponges used as a carrier for rhBMP-2 reduces the amount of rhBMP-2 required to achieve a satisfactory clinical outcome. SUMMARY OF BACKGROUND DATA: Bone morphogenetic proteins (BMPs) although effective in promoting osseous growth and spinal fusion have limitations in their extensive use because of higher costs and possible adverse effects including ectopic bone formation and local inflammatory reaction, particularly in the cervical spine. METHODS: Posterolateral intertransverse process spinal fusion at L4-L5 was performed in Lewis rats. Two doses of BBP (500 microg, and 1000 microg) were tested with or without "low dose" (1 microg) rhBMP-2 and the results were compared with the low dose (1 microg) rhBMP-2. Fusion was evaluated by radiology, histology, and manual palpation tests. RESULTS: Radiology revealed significant earlier fusion with 1000 microg BBP + 1 microg BMP-2 combination when compared with low dose BMP-2 (1 microg) only (P < 0.05). Manual palpation and histology at eighth week revealed higher rate of fusion with the same combination with a nearly significant difference (P = 0.057). CONCLUSION: Specific growth factor binding agents, such as BBP, can be compounded into carriers used in fusion procedures to decrease the dosage of BMP and possibly decrease the side effects which are most likely dose-related. This may also decrease costs and improve clinical outcomes.

A novel application of high-dose (50kGy) gamma irradiation for demineralized bone matrix: effects on fusion rate in a rat spinal fusion model.

BACKGROUND CONTEXT: The safety of allograft material has come under scrutiny because of recent reports of allograft-associated bacterial and viral infections in tissue recipients. Gamma irradiation, although being one of the most effective ways of terminal sterilization, has been shown to affect the biomechanical properties of allograft bone. It may also have detrimental effects on the osteoinductivity of allograft material such as demineralized bone matrix (DBM) by the denaturation of proteins because of heat generated by irradiation. Sterilization of DBM material is an important variable in processing graft materials. This is considered to be one of the factors leading to different fusion rates observed with different commercially available DBM products, as the sterilization procedure itself may affect the osteoinductivity of the material. Currently, there is no ideal sterilization technique that limits the detrimental effect on osteoinductivity and fusion rates. PURPOSE: To evaluate the effects of a range of hydrogen peroxide exposures with or without the controlled high-dose gamma irradiation after processing with radioprotectant solutions (Clearant radiation sterilization procedure) on the fusion rates of human DBM. STUDY DESIGN: A prospective in vivo animal study. METHODS: Eighty mature athymic nude female rats were used for this study, which formed 10 equal groups. Human DBM exposed to hydrogen peroxide for different time periods (0, 1, 6, and 24 hours) was divided into two major subgroups. One group was further treated with controlled high-dose radiation using radioprotectants (radiation treated), whereas the other group was frozen immediately without specific treatment (non-radiation treated). Both radiation-treated and non-radiation-treated DBM material from each group of hydrogen peroxide exposure times were implanted between L4 and L5 transverse processes of the rats forming eight test groups including eight animals in each. The remaining 16 rats were divided into two additional groups to form negative (only decortication, n=8) and positive (bone morphogenetic protein [BMP]-2, n=8) control groups. The rats were evaluated for fusion by radiographs (2, 4, and 8 weeks), manual palpation (8 weeks), and histological analysis after sacrificing. Comparison of fusion rate among all groups was made using these three evaluation methods. RESULTS: Increasing the time period of hydrogen peroxide (0, 1, 6, or 24 hours) exposure for preparation of DBM from bone allograft did not affect the fusion rates significantly (p<.05), although there was a trend toward decreasing fusion rates with longer exposure times. When the hydrogen peroxide washed DBM preparations were also radiation treated, the resulting fusion rates were again not significantly different (p<.05). Agreement among fusion detection methods was found to be high. CONCLUSIONS: Hydrogen peroxide processing was not detrimental to fusion rates. The additional terminal sterilization technique with special gamma irradiation protocols (Clearant process) also did not decrease the fusion rates but could provide an additional margin of safety.

Mechanism of abstraction reactions of heavy cyclopropenes with carbon tetrachloride.

The potential energy surfaces for the abstraction reactions of heavy cyclopropenes (X-Y-Z) with carbon tetrachloride have been characterized in detail using density functional theory (B3LYP), including zero-point corrections. Five cyclopropene analogues including A(C-C-C), B(Ge-Si-Si), C(Si-Si-Si), D(Si-Si-Ge), and E(Ge-Ge-Ge), have been chosen in this work as model reactants. Two reaction paths, the Cl abstraction I and the CCl3 abstraction II, have been considered in the present study. Our theoretical findings strongly suggest that the former is more favorable, with a very low activation energy and a large exothermicity. This is in accordance with available experimental observations. Moreover, our theoretical investigations also indicate that the more electropositive the elements making up the double bond of a heavy cyclopropene, the lower its activation barrier and the more exothermic the haloalkane abstraction. That is, electronic factors play a dominant role in determining the chemical reactivity of the heavy cyclopropene species kinetically as well as thermodynamically. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. The results obtained allow a number of predictions to be made.

The mechanism of C--X (X=F, Cl, Br, and I) bond activation in CX4 by a stabilized dialkylsilylene.

The potential-energy surfaces for the abstraction and insertion reactions of dialkylsilylene with carbon tetrahalides (CX4) have been characterized in detail using density functional theory (B3LYP), including zero-point corrections. Four CX4 species, CF4, CCl(4), CBr4, and CI(4), were chosen as model reactants. The theoretical investigations described herein suggest that of the three possible reaction paths, the one-halogen-atom abstraction (X abstraction), the one-CX3-group abstraction (CX3 abstraction), and the insertion reaction, the X-abstraction reaction is the most favorable, with a very low activation energy. However, the insertion reaction can lead to the thermodynamically stable products. Moreover, for a given stable dialkylsilylene, the chemical reactivity has been found to increase in the order CF4<

Theoretical designs for neutral five-membered carbene analogues of the group 13 elements: a new target for synthesis.

Potential energy surfaces for the chemical reactions of neutral five-membered group 13 carbenoids have been studied using density functional theory (B3LYP/LANL2DZ). Five five-membered group 13 carbenoid species, HCMeP(PhN)2X, where X = B, Al, Ga, In, and Tl, have been chosen as model reactants in this work. Also, three kinds of chemical reaction, C-H bond insertion, alkene cycloaddition, and dimerization, have been used to study the chemical reactivities of these group 13 carbenoids. Our present theoretical work predicts that the larger the angleNXN bond angle in the neutral five-membered group 13 carbenoid, the smaller the singlet-triplet splitting, the lower the activation barrier, and, in turn, the more rapid are its various chemical reactions. Moreover, the theoretical investigations suggest that the relative carbenoidic reactivity decreases in the order B > Al > Ga > In > Tl. That is, the heavier the group 13 atom (X), the more stable is its carbenoid with respect to chemical reactions. As a result, we predict that the neutral five-membered group 13 carbenoids (X = Al, Ga, In, and Tl) should be stable, readily synthesized, and isolated at room temperature. Furthermore, the neutral five-membered group 13 carbenoid singlet-triplet energy splitting, as described in the configuration mixing model attributed to the work of Pross and Shaik, can be used as a diagnostic tool to predict their reactivities. The results obtained allow a number of predictions to be made.

Salvage procedures for failed compression hip screw fixation of intertrochanteric femoral fractures: analysis of 50 cases.

We retrospectively studied 50 patients who underwent salvage procedures for failed compression hip screw (CHS) fixation of intertrochanteric fractures from January 1991 to July 2000. Among these patients, seven underwent revision fixed angle plate surgery; 16 patients underwent bipolar hemiarthroplasty; five patients underwent Austin-Moore hemiarthroplasty; another nine patients underwent total hip arthroplasty; and 13 patients underwent removal of the implant. The age, gender, type of falling accident, osteoporosis status and post-operative ambulation status were recorded. The incidence of failed fixation of CHS was estimated at around 9.7%. A fall was recorded in 52% of cases. There was a significant difference in osteoporosis grade between the failed and successful CHS groups (p < 0.005). There was also better postoperative ambulation in the total hip replacement group compared to the other groups (p = 0.03). Surgical management of nonhealed intertrochanteric fractures is a challenge to orthopedic surgeons. The authors suggest multiple factors, such as fracture geometry, bone quality, preservation of acetabulum cartilage and individual patient factors, be considered when performing salvage procedures for failed CHS.