An approximate solution for a system with a symmetric matrix

In this paper, a large system with a symmetric and essentially (2,2)-band matrix is reformulated as the product of two banded matrices for the purpose of obtaining a solution of a linear system more efficiently. An error term for the approximate solution is justified in the spirit of the work by Yan and Chung [1].     

The single helix in protein L is largely disrupted at the rate-limiting step in folding

To investigate the role of helix formation in the folding of protein L, a 62 residue alpha/beta protein, we studied the consequences of both single and multiple mutations in the helix on the kinetics of folding. A triple mutant with 11 additional carbon atoms in core residues in the amino-terminal portion of the helix folded substantially faster than wild type, suggesting that hydrophobic association with residues elsewhere in the protein occurs at the rate-limiting step in folding. However, helix-destabilizing mutations had little effect on the rate of folding; in particular, a triple glycine substitution on the solvent-exposed side of the helix increased the unfolding rate 56-fold while reducing the folding rate less than threefold. Thus, in contrast to the predictions of models of folding involving the coalescence of well-formed secondary structure elements, the single helix in protein L appears to be largely disrupted at the rate-limiting step in folding and unfolding.     

Development of polylactide microspheres for protein encapsulation and delivery

The development of injectable microparticles for protein delivery is a major challenge. We demonstrated the possibility of entrapping human serum albumin (HSA) and thrombin (Thr) in poly(ethylene glycol) (PEG)‐coated, monodisperse, biodegradable microspheres with a mean diameter of about 10 μm. In our earlier studies, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis was used to characterize the surface of PEG‐coated, taxol‐loaded poly(lactic acid) (PLA) microspheres. An analysis by DRIFTS revealed that PEG was incorporated well on the PLA microsphere surface. An emulsion of protein (in water) and PLA dissolved in an acetone–dichloromethane (or acetone–chloroform) mixture were poured into an aqueous solution of PEG [or poly(vinyl alcohol) (PVA)] with stirring with a high‐speed homogenizer for the formation of microparticles. HSA recovery in microspheres ranged from 13 to 40%, depending on the solvent and emulsification systems used for the preparation. PLA dissolved in a dichloromethane/acetone system and albumin loaded via a PEG emulsification solution (PLA–PEG–HSA) showed maximum drug recovery (39.5%) and drug content (9.9%). Scanning electron microscopy revealed that PEG‐coated microspheres had less surface micropores than PVA‐based preparations. The drug‐release behavior of microspheres suspended in phosphate‐buffered saline exhibited a biphasic pattern. An initial burst release (30%) followed by a constant slow release for 20 days was observed for HSA and Thr from PLA–PEG microspheres. PEG‐coated PLA microspheres show great potential for protein‐based drug delivery. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1285–1295, 2002     

Clinical application of the Mycobacterium tuberculosis direct test: case report, literature review, and proposed clinical algorithm

PURPOSE: A prospective, multiinstitutional trial was initiated in 1991 to examine the tolerance to and efficacy of a program of preoperative chemoradiotherapy (CTRT) and surgical resection for patients with localized adenocarcinoma of the pancreas. PATIENTS AND METHODS: Fifty-three patients were assessable for analysis, with a median follow-up of 52 months for survivors. Radiation therapy (RT) totaling 5,040 cGy in 180 cGy fractions with mitomycin 10 mg/m2 day 2 and fluorouracil (5-FU) 1,000 mg/m2/d continuous infusion days 2 through 5 and 29 through 32 were given as preoperative adjuvant therapy. Twelve patients did not proceed to surgery (one death, one toxicity, three local progression, six distant metastases, one intercurrent illness), whereas 41 patients underwent surgery. Of these, 17 patients did not have resection (11, hepatic and/or peritoneal metastases and six local extension that precluded resection). Twenty-four patients had tumor resection (19 Whipple, four total pancreatectomy, one distal pancreatectomy). RESULTS: Treatment toxicity was primarily hematologic, although a comparable number suffered biliary tract complications, either from obstruction or cholangitis as a result of an occluded stent or the primary tumor. There was one postoperative death. Median survival for the entire group and for the 24 patients with resection was 9.7 and 15.7 months. This survival rate reflected the advanced state of most resected cancers (positive peritoneal cytology, three patients; margins within 2 mm, 13 patients; involved lymph nodes, four patients; and need for superior mesenteric vein (SMV) resection, four patients). Tumor progression was most frequent at metastatic sites. CONCLUSION: This preoperative CTRT protocol was feasible and safe in a cooperative group setting. Entry of patients with advanced tumors probably accounted for the suboptimal resectability and survival results.     

ALAN TURING'S VISIT TO DAYTON

Recently declassified documents from the “Crane Collection” at the National Archives (USA) reveal much of the purpose of Alan Turing's visit to the United States during the Winter of 1942–1943. The “Bombe Correspondence” file contains Turing's “Visit To National Cash Register Corporation of Dayton, Ohio” and additional material which places this report and his earlier “Treatise on the Enigma” in the context of his role as consultant to the U. S. Navy Cryptanalytic Section (Op-20-G) on the design of the Navy Bombe and other related matters. The documents in this collection reveal a productive and decisive relationship between Turing and Op-20-G dating from the visit of the Sinkov mission to Bletchley Park in February 1941.     

THE DIPLOMACY OF SECURITY: BEHIND THE NEGOTIATIONS OF ARTICLE 18 OF THE SINO-AMERICAN COOPERATIVE AGREEMENT

In early February, 1942, Commander M. E. Miles proposed the establishment of a radio intelligence unit in China. His proposal led to the creation of Naval Group China (NGC), the umbrella organization for units that performed weather forecasting, advised and trained Chinese guerillas, and intercepted and analyzed Japanese radio traffic. NGC was part of the Sino-American Cooperative Organization (SACO). Most of the commitments of China and NGC were formalized on 15 April 1943 with the signing of the Sino-American Cooperative Agreement (SACO). Article 18 required further delicate negotiations between Miles and General Tai Li, head of the Bureau of Investigation and Statistics (China's secret service). Miles was soon trapped between his commitment to Tai Li and Joseph Wenger's concern that any intercepted traffic shared with the Chinese would quickly become available to the Japanese via insecure Chinese codes. Fleet Radio Unit, China (FRUCHI) resolved this dilemma.     

RESPONSE OF SOME SCOLYTIDS AND THEIR PREDATORS TO ETHANOL AND 4-ALLYLANISOLE IN PINE FORESTS OF CENTRAL OREGON

Lindgren multiple funnel traps were set up in pine forests of central Oregon to determine the response of scolytid bark beetles to ethanol and 4-allylanisole (4AA). Traps were baited with two release rates of ethanol (4.5 or 41.4 mg/hr) and three release rates of 4AA (0, 0.6, or 4.3 mg/hr) in a 2 × 3 factorial design. All traps also released a 1:1 mixture of - and -pinene at 11.4 mg/hr. Of 13,396 scolytids caught, Dendroctonus valens made up 60%, Hylurgops spp. 18.5%, Ips spp. 16%, Hylastes spp. 1.8%, Ganthotrichus retusus 0.9%, and bark beetle predators another 2.8%. Increasing the release rate of ethanol in the absence of 4AA increased the number of most scolytid species caught by 1.5–3.7 times, confirming its role as an attractant. Ips latidens, Temnochila chlorodia, and clerid predators were exceptions and did not show a response to higher ethanol release rates. Release of 4AA at the lowest rate inhibited attraction of most scolytids, with a significant reduction in G. retusus, Hylastes macer, and Hylurgops porosus when compared to traps without 4AA. A high release rate of 4AA further inhibited responses for most beetles compared to low 4AA. Seven species were significantly deterred by high 4AA, including the latter three, and Hylastes longicollis, Hylastes nigrinus, Hylurgops reticulatus, and Ips latidens. Exceptions include Hylurgops subcostulatus, which was significantly attracted to both low and high 4AA, and I. pini, which was attracted to low and high 4AA in combination with low ethanol, but unaffected by either release of 4AA with high ethanol. Dendroctonus valens was significantly attracted to low 4AA and unaffected by high 4AA. Predators appeared to be less inhibited by 4AA than most bark beetles. Although 4AA can deter the attraction of some secondary bark beetles to ethanol in combination with - and -pinene, this inhibition could be weakened for certain species by increasing ethanol release rates. 4-Allylanisole may have some utility for managing the behavior of secondary bark beetles sensitive to this compound.     

CREEP, FATIGUE AND CREEP-FATIGUE CRACK GROWTH RATES IN PARENT AND SIMULATED HAZ TYPE 321 STAINLESS STEEL

Abstract— Crack growth rate data are presented from a range of fully reversed displacement-controlled fatigue and creep-Fatigue tests and from static load-controlled creep crack growth tests on aged 321 stainless steel (parent and simulated HAZ) at 650 ° C. In the creep fatigue tests, constant displacement tensile hold periods of 12–192 h were used. Crack growth rates comprised both cyclic and dwell period contributions. Cyclic growth contributions are described by a Paris-type law and give faster crack growth rates than those associated with pure fatigue tests. Dwell period contributions are described by the C* parameter. The total cyclic crack growth rates are given by summing the cyclic and dwell period contributions. Estimates of C* using a reference stress approach together with the appropriate stress relaxation creep data are shown to correlate well with experimentally measured C* values. Crack growth rates during static load-controlled tests correlate well with C* . Good agreement is obtained between crack growth rates during the static tests and those produced during the hold period of the creep-fatigue tests.