Dilution methods to deprive Chlamydomonas reinhardtii cultures of sulfur for subsequent hydrogen photoproduction

Sulfur deprivation of Chlamydomonas reinhardtii cultures gradually inactivates photosynthetic O₂ evolution and leads to the establishment of anaerobiosis in the medium. Sulfur-deprived algal cultures kept under anaerobic conditions will then produce H₂ gas for 3–5 days under continuous illumination. Currently, sulfur deprivation is achieved by mechanical centrifugation of cultures grown in sulfur-replete medium, followed by extensive and costly washing. The cells are finally resuspended in sulfur-free medium. The current study investigates two procedures to deprive algal cultures of sulfur that eliminate the centrifugation step. These procedures involve sulfur deprivation by dilution of sulfur-replete cultures into either sulfur-limited medium or sulfur-free medium. We demonstrate that efficient H₂ photoproduction can be achieved on a timely basis using either procedure. However, the dilution of sulfate-replete algal cultures 1:10 v/v into sulfur-free medium is the most appropriate procedure. These observations serve as the basis for developing an algal H₂-production system that is cheaper, less time-consuming, and less amenable to contamination with other microorganisms than systems employing centrifugation for sulfur deprivation.     

Demonstration of sustained hydrogen photoproduction by immobilized,sulfur-deprived Chlamydomonas reinhardtii cells

It was demonstrated that immobilized, sulfur-deprived algal cultures can photoproduce H₂${}_2$. After identifying the optimal material and procedures for immobilization of Chlamyodomonas reinhardtii   at high cell density, we examined the effect of liquid mixing, sulfate content, acetate levels and light intensity on the H₂${}_2$-production activity of the culture. Our results indicate that (a) liquid mixing is important to provide homogeneous conditions for the immobilized culture; (b) sulfur deprivation is necessary for hydrogen production by immobilized cultures; and (c) high light intensity decreases H₂${}_2$ production. The maximum total volume of H₂${}_2$ produced by the system (160 ml of reactor volume) was 380 ml over 23 days, and the highest rate of H₂${}_2$ production observed was 45 ml day^-1${}^{-1}$. Cell immobilization significantly increased the duration of the H₂${}_2$-photoproduction phase (up to 4 weeks), maintained specific rates of H₂${}_2$ photoproduction similar to those of suspension cultures and showed potential for large increases in H₂${}_2$ production.     

Control mapping in virtual reality: effects on spatial presence and controller naturalness

Virtual Reality - This study explores how a video game player’s sense of being in a game world (i.e., spatial presence) is impacted by the use of a virtual reality head-mounted display (VR...     

Are complications in cruciate ligament replacement operations with patellar tendon transplantation dependent on surgical technique and surgical timing?

HYPOTHESIS: In a retrospective study we analyzed our results of ACL reconstructions with a patellar tendon graft. We wanted to know if the complications were dependent upon timing and technique of surgery. METHOD: We reviewed 283 patients after ACL-reconstruction, who underwent an operation with bone patellar tendon graft between 1984-1993. In our study we particularly looked for complications. The overall rate of complications was 21.6% dependent on the applied technique. Infections, DVTs, limitations of movement and graft failures were the most common complications. Furthermore we analyzed the timing of operation. Arthrofribrosis was less common in the group with delayed reconstruction (6.1%) whereas in the primary reconstruction group the rate was 17.6%. For this reason we changed our management with regard to the timing of operation. Meniscal injuries were the most common additional injuries in both groups. Conservatively treated ACL-ruptures showed a high rate of mensical ruptures in combination with cartilage injuries. CONCLUSION: Because of these results we put more emphasis on patient information to achieve the optimal result and to meet the individual needs for every patient.     

Inhibition of cyclooxygenase-2 rapidly reverses inflammatory hyperalgesia and prostaglandin E2 production

PGs derived from cyclooxygenase-2 (COX-2), in particular PGE2, play important roles in the initiation of inflammation and pain. In the present study, we evaluated the role of COX-2-derived PGE2 in an animal model of established hyperalgesia. Inflammation and hyperalgesia were first induced by injection of carrageenan into rat footpads. Then we investigated the effects of subsequent therapeutic treatment with a selective COX inhibitor, with a nonsteroidal anti-inflammatory drug and with anti-PGE2 antibody. Test compounds were administered 1 to 3 hr after carrageenan challenge, and inhibition of pain (hyperalgesia, measured by withdrawal from a thermal stimulus), and changes in paw edema and PG levels were evaluated. The i.v. administration of a nonselective COX inhibitor, ketorolac, caused a rapid reduction in hyperalgesia in the inflamed footpad, returning it to near-normal values within 1 hr. Normal (control) paw response times were not affected. Therapeutic administration of ketorolac prevented most further swelling caused by carrageenan but did not reverse edema already present at the time of dosing. Administered p.o., a selective COX-2 inhibitor (SC-58635) was as efficacious as ketorolac in reducing inflammatory hyperalgesia. Footpad PG levels returned to base line or below within 5 min of dosing with ketorolac, which suggests rapid turnover of PG in the inflamed tissue. Therapeutic treatment with a monoclonal anti-PGE2 antibody also fully reversed the hyperalgesia response. These studies suggest that continuous production of PGE2 by the COX-2 enzyme is a critical element in sustaining the hyperalgesic response at sites of tissue inflammation.     

Improvement of HLA class I and class II PCR-SSP typing by using timed-release activity of DNA polymerase

These are hard times for medical school deans--high turnover among deans, the fiscal distress of many medical schools, the gap between what deans expect the job will be and what is required of them, the stark differences between what the job of dean is today and what it was in the past, and the threats to the academic missions of education and research. Using stories, anecdotes, and parables, the authors illustrates how these very difficulties might be an opportunity to rethink the role of deans and to re-examine the attributes and skills required of successful deans today. The ultimate goals of medical education have not changed, but the drastic nature of the changes taking place all around, and within, medical education make it more critical than ever to keep in mind what is really important. Deans must be exquisitely attuned to what is really important and they must make sure that the academic medical community never loses sight of what that is. To do that, deans must be deeply rooted personally in the enduring values and commitments that inform medicine as a profession and a vocation and in the fundamental values of medical education and scholarship; they must personify and embody these values; and they must remind us of these values and inspire us to embrace them and be guided by them. This is the sense in which deans must be "spiritual" leaders--that is, through their personal example, they must rekindle and engage the spirit of those working on behalf of the academic mission. While the need for fiscal expertise, management skills, and diplomatic and interpersonal skills in deans is widely acknowledged, the need for sensitivity to the spiritual dimensions of the work of deans has not received the attention it deserves.     

Clinical experience with the technetium-99 scan in children

A study of 86 bone scans in 79 patients was conducted to determine ways to enhance the usefulness of this test and learn what factors influence its results. While the overall value of the bone scan as we initially used it was not what we had hoped, it could be improved substantially by utilizing all initial clinical information when ordering as well as interpreting the scan. Its main value in suspected sepsis is to localize affected areas in and around the pelvis and spine. The scan is often unnecessary in the diagnosis of long-bone osteomyelitis and is seldom indicated when diagnosing cellulitis or synovitis. In occult trauma it is valuable for further investigation of specific areas with possible nondisplaced fractures. Needle aspiration of the bone or joint does not seem to alter the scan. We conclude that the bone scan is chiefly valuable in locating focal areas of skeletal pathophysiology.