The performance of a direct-sequence spread-spectrum acquisition system using a linear prediction filter for narrowband interference suppression

The coarse acquisition performance of a direct sequence spread-spectrum receiver is analyzed when a linear prediction filter is used for narrowband interference suppression. We show that once an appropriate matching strategy is identified, the linear prediction filter can provide favorable performance when narrowband interference is present over a considerable range of both interference power and bandwidth. In addition, the presence of the filter dramatically improves the performance over the case where there is no filter, except when the interference bandwidth and the power are both small (i.e., when the processing gain provides sufficient interference immunity without the filter). If long spreading sequences are used with moderately sized observation windows, the acquisition performance can be severely degraded when a parallel acquisition scheme is used due to the linear predication filter. We show, however, that a slower serial receiver will provide reliable performance.This work was supported in part by the Office of Naval Research under contract ONR N00014-91-J-1234, the Army Research Office under contract ARO DAAL03-91-0071, and the NSF Center for Ultra-High Speed Circuits and Systems (ICAS).     

Broadband CDMA for personal communications systems

Multipath propagation in a broadband CDMA environment is described. A propagation model for broadband spread-spectrum signals is presented. Experimental results relating to the sharing of the band by fixed service microwave users and mobile personal communications network (PCN) users are discussed. Field tests indicate that PCN systems can provide high-quality communications when sharing the spectrum with fixed-service microwave systems in suburban and urban areas     

Error-resilient video communications over CDMA networks with a bandwidth constraint.

We present an adaptive video transmission scheme for use in a code-division multiple-access network, which incorporates efficient bandwidth allocation among source coding, channel coding, and spreading under a fixed total bandwidth constraint. We derive the statistics of the received signal, as well as a theoretical bound on the packet drop rate at the receiver. Based on these results, a bandwidth allocation algorithm is proposed at the packet level, which incorporates the effects of both the changing channel conditions and the dynamics of the source content. Detailed simulations are done to evaluate the performance of the system, and the sensitivity of the system to estimation error is presented.     

Hybrid pulse position modulation/ultrashort light pulse code-division multiple-access systems .I. Fundamental analysis

We propose a hybrid pulse position modulation/ultrashort light pulse code-division multiple-access (PPM/ULP-CDMA) system for ultrafast optical communications. The proposed system employs spectral CDMA encoding/decoding and PPM with very short pulse separation. The statistical properties of the encoded ULP are investigated with a general pulse model, and the performance of the proposed PPM/ULP-CDMA system is investigated. It is shown that we can improve upon the performance of other ULP-CDMA systems, such as those using on-off keying, by employing PPM. It is also shown that we can improve the performance of the proposed system by increasing the effective number of chips, by increasing the number of PPM symbols, and by reducing the ULP duration. The performance analysis shows that the aggregate throughput of the proposed PPM/ULP-CDMA system could be over 1 Tb/s.     

Relation between hardness and compressive strength of polymer concrete

Experimental studies were made of the influence of mixing and casting techniques and of curing time upon the compressive strength and hardness of methyl methacrylate based polymer concrete. The Rockwell K and F scales were found to be suitable for the hardness determinations. Over a wide range of hardness and strength values, the average compressive strength (f_c) varied linearly with the average hardness (R_K) according to the relation f_c (psi) = 560 R_K - 12000, irrespective of casting and curing variables. The weaker materials exhibited greater variations in hardness. Hardness testing is found to provide a meaningful and convenient method for evaluating the quality of polymer concrete.     

The Effect of Hypoxia on the Expression of CXC Chemokines and CXC Chemokine Receptors—A Review of Literature

Hypoxia is an integral component of the tumor microenvironment. Either as chronic or cycling hypoxia, it exerts a similar effect on cancer processes by activating hypoxia-inducible factor-1 (HIF-1) and nuclear factor (NF-κB), with cycling hypoxia showing a stronger proinflammatory influence. One of the systems affected by hypoxia is the CXC chemokine system. This paper reviews all available information on hypoxia-induced changes in the expression of all CXC chemokines (CXCL1, CXCL2, CXCL3, CXCL4, CXCL5, CXCL6, CXCL7, CXCL8 (IL-8), CXCL9, CXCL10, CXCL11, CXCL12 (SDF-1), CXCL13, CXCL14, CXCL15, CXCL16, CXCL17) as well as CXC chemokine receptors—CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, CXCR7 and CXCR8. First, we present basic information on the effect of these chemoattractant cytokines on cancer processes. We then discuss the effect of hypoxia-induced changes on CXC chemokine expression on the angiogenesis, lymphangiogenesis and recruitment of various cells to the tumor niche, including myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), regulatory T cells (T_regs) and tumor-infiltrating lymphocytes (TILs). Finally, the review summarizes data on the use of drugs targeting the CXC chemokine system in cancer therapies.     

Inhibitors of Cyclin-Dependent Kinases: Types and Their Mechanism of Action

Recent studies on cyclin-dependent kinase (CDK) inhibitors have revealed that small molecule drugs have become very attractive for the treatment of cancer and neurodegenerative disorders. Most CDK inhibitors have been developed to target the ATP binding pocket. However, CDK kinases possess a very similar catalytic domain and three-dimensional structure. These features make it difficult to achieve required selectivity. Therefore, inhibitors which bind outside the ATP binding site present a great interest in the biomedical field, both from the fundamental point of view and for the wide range of their potential applications. This review tries to explain whether the ATP competitive inhibitors are still an option for future research, and highlights alternative approaches to discover more selective and potent small molecule inhibitors.     

Solubility and Aggregation of Selected Proteins Interpreted on the Basis of Hydrophobicity Distribution

Protein solubility is based on the compatibility of the specific protein surface with the polar aquatic environment. The exposure of polar residues to the protein surface promotes the protein’s solubility in the polar environment. The aquatic environment also influences the folding process by favoring the centralization of hydrophobic residues with the simultaneous exposure to polar residues. The degree of compatibility of the residue distribution, with the model of the concentration of hydrophobic residues in the center of the molecule, with the simultaneous exposure of polar residues is determined by the sequence of amino acids in the chain. The fuzzy oil drop model enables the quantification of the degree of compatibility of the hydrophobicity distribution observed in the protein to a form fully consistent with the Gaussian 3D function, which expresses an idealized distribution that meets the preferences of the polar water environment. The varied degrees of compatibility of the distribution observed with the idealized one allow the prediction of preferences to interactions with molecules of different polarity, including water molecules in particular. This paper analyzes a set of proteins with different levels of hydrophobicity distribution in the context of the solubility of a given protein and the possibility of complex formation.