Air management modeling of condensing units in a confined space and its impact on the chiller system performance

The small air cooled chillers that serve an apartment building or residential villa often have the outdoor condensing units installed within a confined space. The installation distance between chiller and wall or between two chillers has significant impact on the chiller performance. In this study, three CFD (Computational Fluid Dynamics) approaches to condensing unit air management modeling are proposed and compared with each other first. The predicted air flow rates are compared to the test data as well. The comparison shows that the CFD approach with fan boundary definition is the most cost-effective, easy to be implemented, and accurate. Together with the chiller system modeling, a parametric study is further conducted to investigate the effect of the wall-chiller distance and the chiller-chiller distance on the chiller performance.     

Difference in pain relief after trigger point injections in myofascial pain patients with and without fibromyalgia

OBJECTIVE: To compare responses to trigger point (TrP) injection between patients having both myofascial pain syndrome (MPS) caused by active TrPs and fibromyalgia syndrome (FMS) and patients with MPS due to TrPs but without FMS. DESIGN: Prospective design blinded measurement, before- after trial. SETTING: A pain control medical clinic. PATIENTS: Group 1: MPS + FMS; Group 2: MPS only. All patients (9 in each group) had active TrPs in the upper trapezius muscle. INTERVENTION: Myofascial TrP injection with 0.5% xylocaine. MAIN OUTCOME MEASURES: Subjective pain intensity (PI), pain threshold (PT), and range of motion (ROM) were assessed before, immediately after, and 2 weeks after TrP injection. RESULTS: In a comparison of preinjection measures to immediate postinjection measures, only ROM was significantly improved (p < .05) in Group 1 patients; all three parameters were significantly improved (p < .05) in the Group 2 patients who had only MPS. Two weeks after injection, both groups showed significant improvement (p < .05) in all three measured parameters as compared to preinjection measurements. In a comparison of the two groups, the immediate effectiveness of TrP injection was significantly less (p < .05) in Group 1 than in Group 2 for all three parameters. Two weeks after injection, the degree of improvement in PT or ROM (but not PI) was not significantly different between two groups. Postinjection soreness (different from myofascial pain) was more severe, developed sooner, and lasted longer in Group 1 than in Group 2. CONCLUSION: Trigger point injection is a valuable procedure for pain relief for patients in both group. Patients with FMS are likely to experience significant but delayed and attenuated pain relief following injection of their active TrPs compared to myofascial pain patients with similar TrPs but without FMS. Also, FMS patients are likely to experience significantly more postinjection soreness for a longer period of time.     

Gonadal cell apoptosis: hormone-regulated cell demise

We have studied the release of nerve growth factor (NGF), a protein under consideration for treatment of Alzheimer's Disease, from polymer matrices and microspheres to characterize the stability of NGF, the dynamics of NGF release, and the distribution of NGF within the brain interstitium. Poly(ethylene-co-vinyl acetate) (EVAc) disks and poly(L-lactic acid) (PLA) microspheres were formed by codispersing NGF with one of a variety of molecules. The mass of mouse NGF (mNGF) detected following release from EVAc disks into buffered saline varied five-fold over the range of codispersants studied, with carboxymethyldextran providing optimal release, while the mass of recombinant human NGF (rhNGF) released varied four-fold from both EVAc disks and PLA microspheres, with albumin and carboxymethyldextran providing optimal release. Variation of the codispersant species significantly affected NGF release into buffered saline; it also had a noticeable, but small, effect of the amount of NGF found in the brain tissue following implantation of a polymer device. To improve NGF retention in tissue, NGF was conjugated to 70,000 molecular weight dextran and incorporated into a polymeric device. The distribution of NGF was enhanced by conjugation; comparison of NGF concentrations in the brain to a mathematical model of diffusion and elimination suggested that the elimination rate of NGF-dextran conjugate in the tissue was over seven times slower than the elimination rate of NGF. These results indicate that variation of the properties of the controlled release system may be useful in regulating the time course of NGF delivery to tissue, and that modification of the NGF itself can improve penetration and retention in the brain.     

Bandwidth-reservation scheme based on road information for next-generation cellular networks

Channel-reservation techniques have been widely studied in cellular networks in order to meet the desired quality-of-service requirements. In this paper, a distributed predictive channel-reservation scheme, called the road-map-based channel-reservation scheme (RMCR), and a call-admission-control algorithm are proposed. The goal is to reduce the handoff-dropping probability and to improve the bandwidth utilization. In the RMCR scheme, we assume that base stations (BSs) are equipped with road-map information and that mobile stations (MSs) are equipped with global positioning systems (GPS) devices. MSs periodically report their GPS location information to their BSs. Based on the location information of the MSs at two consecutive epochs, the BSs estimate the speed and moving direction of the MSs. Furthermore, the BSs estimate the probability that the MSs will enter the neighboring cells based on their velocity and the road-map information stored in the BSs. The BSs then compute the amount of bandwidth to be reserved, based on such estimation. With the road-map information, the BSs can make a more-accurate prediction on the user's mobility and, hence, reduce unnecessary bandwidth reservation. Simulation results show that RMCR is capable of keeping the handoff-dropping probability low and allocating bandwidth to new/handoff calls efficiently. We also show that RMCR is robust with respect to system parameters such as user's speed, the density of roads, the accuracy of mobility measurement, and so on.     

Analysis of Field Data on Computer Failures

This paper emphasizes the importance of making field measurements for effective and realistic dependability evaluatians.Two examples are given,both based on real data from IBM mainframes.The first evaluates the imnact of the operating environment on system failure characteristics and the second shows how an accurate model depicting this interaction can be extracted from real data.     

Drain-engineered hot-electron-resistant device structures: a review

Various MOS structures with specially designed drain regions are reviewed. Guidelines are established for the fabrication of hot-electron-resistant device structures. Additionally, suggestions are made with reference to device structures suitable for a manufacturing environment     

Demonstration and system analysis of the HORNET architecture

The HORNET architecture is a packet-over-wavelength-division-multiplexing ring network that utilizes fast-tunable packet transmitters and wavelength routing to enable it to scale cost-effectively to ultrahigh capacities. In this paper, we present the HORNET architecture and a novel control-channel-based media access control protocol. The survivability of the architecture is demonstrated with an experimental laboratory testbed. Mathematical analysis of the architecture shows that the wavelength routed network can scale to relatively large sizes ranging between 30 and 50 nodes, depending on the component performance. This is true even for arrangements that do not contain high-power optical amplifiers in every node.     

Disulfide-linked head-to-head multimerization in the mechanism of ion channel clustering by PSD-95

The PSD-95/SAP90 family of PDZ-containing proteins is directly involved in the clustering of specific ion channels at synapses. We report that channel clustering depends on a conserved N-terminal domain of PSD-95 that mediates multimerization and disulfide linkage of PSD-95 protomers. This N-terminal multimerization domain confers channel clustering activity on a single PDZ domain. Thus, channel clustering depends on aggregation of PDZ domains achieved by head-to-head multimerization of PSD-95, rather than by concatenation of PDZ domains in PSD-95 monomers. This mechanism predicts that PSD-95 can organize heterogeneous membrane protein clusters via differential binding specificities of its three PDZ domains. PSD-95 and its relative chapsyn-110 exist as disulfide-linked complexes in rat brain, consistent with head-to-head multimerization of these proteins in vivo.