bluuebunny/crossref_metadata_2025 huggingface dataset:
Terahertz wave properties of alumina microphotonic crystals with a diamond structure
Authors: Kanaoka Hideaki , Kirihara Soshu , Miyamoto Yoshinari
Published: March 2008

Fabrication and terahertz wave properties of alumina microphotonic crystals with a diamond structure were investigated. The three-dimensional diamond structure was designed on a computer using 3D-CAD software. The designed lattice constant was 500 μm. The structure consisted of 8 × 8 × 4 unit cells. Acrylic diamond structures with an alumina dispersion of 40 vol% were formed by using microstereolithography. Fabricated precursors were dewaxed at 600 °C and sintered at 1500 °C. The linear shrinkage ratio was about 25%. The relative density reached 97.5%. The electromagnetic wave properties were measured by terahertz time-domain spectroscopy. A complete photonic band gap was observed at the frequency range from 0.40 THz to 0.47 THz, and showed good agreement with the simulation results calculated by the plane wave expansion method. Moreover, localized modes were obtained at the frequencies 0.42 THz and 0.46 THz by introducing an air defect in the diamond structure. They corresponded to the simulation by the transmission line modeling method.
Structure of layered WSe2 thin films with ultralow thermal conductivity
Authors: Kim Seongwon , Zuo Jian Min , Nguyen Ngoc T. , Johnson David C. , Cahill David G.
Published: March 2008

Crystallographic ordering and defects in WSe2 thin films with ultralow thermal conductivity are characterized by electron imaging and diffraction in cross-sectional geometry. The results show that the film consists of oriented, coherent crystallites that are a few nanometers in diameter. Two films of different thickness with different thermal conductivity are compared. We show that the film with a lower thermal conductivity is characterized by less coherent crystallites with a greater degree of misorientation.
Optical and electrical modeling of thin-film silicon solar cells
Authors: Zeman M. , Krc J.
Published: March 2008

This article focuses on the modeling and simulation of thin-film silicon solar cells to obtain increased efficiency. Computer simulations were used to study the performance limits of tandem and triple-junction, silicon-based solar cells. For the analysis, the optical simulator SunShine, which was developed at Ljubljana University, and the optoelectrical simulator ASA, which was developed at Delft University of Technology, were used. After calibration with realistic optical and electrical parameters, we used these simulators to study the scattering properties required, the absorption in nonactive layers, antireflective coatings, and the crucial role of the wavelength-selective intermediate reflector on the performance of the solar cells. Careful current matching was carried out to explore whether a high photocurrent [i.e., more than 15 mA/cm2for a tandem hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon (μc-Si:H) solar cell and 11 mA/cm2for a triple-junctiona-Si:H/amorphous silicon germanium (a-SiGe:H)/μc-Si:H solar cell] could be obtained. In simulations, the extraction of the charge carriers, the open-circuit voltage, and the fill factor of these solar cells were improved by optimizing the electrical properties of the layers and the interfaces: ap-doped,a-SiC layer with a larger band gap (EG> 2 eV) and buffer layers atp/iinterfaces were used. Simulations demonstrated thata-Si:H/μc-Si:H solar cells could be obtained with a conversion efficiency of 15% or higher, and triple-junctiona-Si:H/a-SiGe:H/μc-Si:H solar cells with an efficiency of 17%.
The micro-impact fracture behavior of lead-free solder ball joints
Authors: Huang Y.L. , Lin K.L. , Liu D.S.
Published: March 2008

The present study investigated the micro-impact fracture behavior of various lead-free solder joints, including Sn–1Ag–0.1Cu–0.02Ni–0.05In, Sn–1.2Ag–0.5Cu–0.05Ni, and Sn–1Ag–0.5Cu. The fracture that occurs within the solder joint corresponds to a higher impact fracture energy (1.35 mJ), while the fracture at the interface between the solder joint and intermetallic compound acquires a smaller impact energy (0.82 mJ). Two types of fracture mechanisms were proposed based on observations of the fracture morphology and the impact curve for the solder ball joints. The longer deflection distance, referring to better elongation, exists for the mechanism corresponding to the higher fracture energy.
Patterning of c-axis-oriented Ba2TiX2O8 (X = Si, Ge) crystal lines in glass by laser irradiation and their second-order optical nonlinearities
Authors: Honma Tsuyoshi , Komatsu Takayuki , Benino Yasuhiko
Published: March 2008

Crystal lines consisting of nonlinear optical fresnoite-type Ba2TiX2O8 (X = Si, Ge) crystals are patterned on the surface of CuO (1 mol%)-doped 33.3BaO–16.7TiO2–50SiO2 or –50GeO2 glasses by continuous-wave (cw) neodymium:yttrium aluminum garnet (Nd:YAG) laser (wavelength 1064 nm) irradiation. It is confirmed from polarized micro-Raman scattering spectra that the c axis of Ba2TiX2O8 crystals in the lines are oriented along the laser-scanning direction (i.e., parallel to the lines). The azimuthal dependences of second-harmonic (SH) intensities for the crystal lines indicate unique fringe patterns, and the c-axis orientation of the crystals is supported from the analyses of fringe patterns. The value of the d31/d33 ratio is found to be ∼23 for Ba2TiSi2O8 (BTS) crystal lines, and ∼13 for Ba2TiGe2O8 (BTG) crystal lines, where d31 and d33 are the principal d tensors for the second-order optical nonlinearity of fresnoite-type crystals.
Self-formed pencil-like bulk composite materials consisting of copper alloy and stainless steel
Authors: Wang C.P. , Liu X.J. , Ohnuma I. , Kainuma R. , Ishida K.
Published: March 2008

On the basis of the CALPHAD (Calculation of Phase Diagrams) method, the compositional range of stable miscibility gap and volume fractions of the two liquid phases in the Cu–Fe–Cr–Ni system were predicted, which can provide the guidance for design of self-formed composite materials. Based on such information, the self-formed pencil-like bulk composite materials consisting of copper alloy and two kinds of stainless steels were prepared by controlling the compositions of Cu-rich and Fe-rich phases in immiscible liquid system by the conventional casting process. The experimental results are in good agreement with the ones predicted by calculation. This study indicates that it is possible to develop the pencil-like bulk composite materials consisting of copper alloy and stainless steels by the conventional casting process.
Microindentation of titanium: Dependence of plastic energy on the indentation depth and time-dependent plastic deformation
Authors: Chen Rong , Yang Fuqian , Imam M. Ashraf , Feng C.R. , Pao Peter
Published: March 2008

The cavity model and the dislocation mechanics were used to analyze the plastic energy dissipated in an indentation deformation. The plastic energy dissipated in an indentation cycle was proportional to the cube of the residual indentation depth. The experimental results supported the analysis for the indentation of commercially pure titanium by a Vickers indenter. Slip bands around the indentation were observed, suggesting that the indentation deformation was controlled by dislocation motion. The indentation hardness decreased with the indentation load, showing the indentation size effect. The ratio of the total energy to the plastic energy was found to be proportional to the ratio of the maximum indentation depth to the residual indentation depth. The effects of holding time were examined on the time-dependent plastic deformation of the commercially pure titanium at ambient temperature.
Self-organized Zn/ZnO core-shelled hierarchical structures prepared by aqueous chemical growth
Authors: Kuan C.Y. , Chou J.M. , Leu I.C. , Hon M.H.
Published: March 2008

Self-assembled core-shelled hierarchical structures consisting of single-crystalline pyramid Zn microtip as a core, converted ZnO coating as the shell, and the grown ZnO nanowires as branches, have been prepared. Such ZnO hierarchical structures fabricated by a simple aqueous chemical growth method on Zn foil substrate are expected to be easily integrated into nanodevices. These self-organized structures are superior to both the random nanoarchitecture arrays formed in vapor system and the precipitated nanostructures suspended in the solution. Because of the easier transportation of electrons from the metallic core to ZnO branches, the self-assembled core-shelled hierarchical structures exhibit better field-emission characteristics.
Fast assembly of bio-inspired nanocomposite films
Authors: Vertlib Viatcheslav , Dietiker Marianne , Plötze Michael , Yezek Lee , Spolenak Ralph , Puzrin Alexander M.
Published: March 2008

This paper presents a spin-coating layer-by-layer assembly process to prepare multilayered polyelectrolyte-clay nanocomposites. This method allows for the fast production of films with controlled layered structure. The preparation of a 100-bilayer film with a thickness of about 330 nm needs less than 1 h, which is 20 times faster than conventional dip-coating processes maintaining the same hardness and modulus values. For validation of this technique, nanocomposite films with thicknesses up to 0.5 μm have been created with the common dip self-assembly and with the spin coating layer-by-layer assembly technique from a poly(diallyldimethylammonium)chloride (PDDA) solution and a suspension of a smectite clay mineral (Laponite). Geometrical characteristics (thickness, roughness, and texture) as well as mechanical characteristics (hardness and modulus) of the clay-polyelectrolyte films have been studied. The spin-coated nanocomposite films exhibit clearly improved mechanical properties (hardness 0.4 GPa, elastic modulus 7 GPa) compared to the “pure” polymer film, namely a sixfold increase in hardness and a 17-fold increase in Young’s modulus.
Specific interaction characteristics in organoclay nanocomposite of miscible poly(styrene-co-acrylonitrile) and poly(vinyl chloride) blend
Authors: Lim Sang-Kyun , Lee Eun-Hee , Chin In-Joo
Published: March 2008

We propose a new method for the preparation of the polymer/organoclay nanocomposite, termed the solution and melt mixing (SOAM) method, where the polymer and clays are first blended in solution, and subsequently the mixture is further blended in the melt. We prepared the ternary nanocomposite systems of poly(styrene-co-acrylonitrile) (SAN), poly(vinyl chloride) (PVC) and Cloisite25A clays (C25A) by solution blending as well as by the SOAM method. The C25A content in the nanocomposite was optimized by analyzing the x-ray diffraction (XRD) data of binary mixtures (SAN/C25A and PVC/C25A nanocomposites). The values of the interaction parameter (χab) were calculated by using the molar attraction constants of the specific functional groups derived from Hoy’s table. While PVC and C25A were shown to be highly compatible, SAN and C25A were less compatible. XRD data and transmission electron microscopy observations indicated that the SAN/PVC/C25A nanocomposites had at least partially exfoliated structures. The tensile modulus and the elongation at break of the nanocomposites prepared by the SOAM method were higher than those prepared by simple solution blending.
Performance Differences between Two Endemic Stocks of Largemouth Bass in South Carolina
Authors: Leitner Jean , Bulak James
Published: March 2008

A common-garden experiment was conducted to compare growth of two stocks of largemouth bass Micropterus salmoides, one from the Coastal Plain and one from the Piedmont region of South Carolina. An equal number of fish from each stock were released at age 0 in Lake Paul Wallace, a 113-ha municipal impoundment in South Carolina's Coastal Plain. Boat electrofishing during spring was used to sample the population at ages 1, 3, and 4. Relative survival, mean length and weight, weight frequency distributions, and weight–length relationships were compared between stocks. The Piedmont stock was significantly larger at age 1, whereas the Coastal Plain stock was larger at ages 3 and 4. The weight frequency distributions differed between stocks, as did the weight–length relationships. The total catch for each stock was not proportionally different from stocking rates at age 1. However, the catch of the Coastal Plain stock was significantly higher at ages 3 and 4, suggesting better survival to those ages. We conclude that these two endemic stocks exhibited different performance at one study site in the Coastal Plain. Further evaluations across regions are needed to better define the performance of these two stocks of largemouth bass and ascertain appropriate stocking regions for each stock.
New Therapeutic Directions for Advanced Pancreatic Cancer: Targeting the Epidermal Growth Factor and Vascular Endothelial Growth Factor Pathways
Authors: Burris Howard , Rocha-Lima Caio
Published: March 2008

Learning Objectives

After completing this course, the reader will be able to: Evaluate the existing chemotherapeutic options for advanced pancreatic cancer.Interpret data from trials of HER-1/EGFR- and VEGFR-targeted agents in advanced pancreatic cancer.Take advantage of the potential of biomarkers in selecting optimal molecular-targeted therapies for advanced pancreatic cancer.

CME Access and take the CME test online and receive 1 AMA PRA Category 1 Credit™ at CME.TheOncologist.com

In advanced pancreatic cancer, single-agent gemcitabine became the standard therapy approximately 10 years ago. Subsequently, combinations of gemcitabine with fluorouracil, cisplatin, irinotecan, oxaliplatin, or pemetrexed produced no clear survival benefit. Among the newer approaches, targeting human epidermal growth factor receptor (HER-1/EGFR) shows promise. The U.S. Food and Drug Administration recently approved erlotinib (a HER-1/EGFR tyrosine kinase inhibitor) combined with gemcitabine for the first-line treatment of advanced pancreatic cancer. This combination showed a statistically significant survival benefit over gemcitabine alone in locally advanced or metastatic disease (the median overall survival time was 6.24 months versus 5.91 months; hazard ratio, 0.82; p = .038); however, the clinical significance of this survival difference has been questioned. Additionally, a large phase III trial where the addition of cetuximab (an anti–HER-1/EGFR monoclonal antibody [mAb]) to gemcitabine failed to result in a longer overall survival time than with gemcitabine alone has been reported. Targeting vascular endothelial growth factor (VEGF) with bevacizumab (a recombinant, humanized IgG1 mAb that binds to VEGF) in combination with gemcitabine was investigated in a phase II trial, with promising outcomes that were unfortunately not supported by a subsequent phase III study. While the future treatment of pancreatic cancer may be influenced by the potential of certain biomarkers to predict better response to molecular-targeted therapies, allowing individualization of patient therapy, there are currently no clear candidates, and this remains an interesting area for further investigation.
What to Do with an Abnormal PSA Test
Authors: Loeb Stacy , Catalona William J.
Published: March 2008

Learning Objectives

After completing this course, the reader will be able to: Take advantage of the use of total PSA thresholds for predicting prostate cancer risk and determining the need for prostate biopsy.Distinguish prostate cancer from benign conditions based on the relative proportions of complexed and free forms.Use PSA density as a means to correct for the effect of prostate volume on the PSA level.Explain the evolving role of PSA kinetics in the prediction of aggressive prostate cancer.Perform the calculations for PSA velocity and PSA doubling time.

CME Access and take the CME test online and receive 1 AMA PRA Category 1 Credit™ at CME.TheOncologist.com

For more than a decade, prostate-specific antigen (PSA) has been used for prostate cancer screening. Over the years, this screening has been continually refined, including investigation into the use of lower total PSA thresholds, PSA isoforms, and PSA kinetics. This review describes the evolution of prostate cancer screening and provides clinical insights into the informed use of PSA and its adjunctive measurements.
Managing Vesicant Extravasations
Authors: Schulmeister Lisa
Published: March 2008

Learning Objectives

After completing this course, the reader will be able to: Describe how vesicant chemotherapy drugs can extravasate from implanted ports.Recommend procedures to obtain a blood return from central venous access devices.Evaluate the signs and symptoms of a vesicant extravasation.Administer the FDA-approved vesicant extravasation treatments and antidotes.

CME Access and take the CME test online and receive 1 AMA PRA Category 1 Credit™ at CME.TheOncologist.com

Extravasation is an unusual but potentially severe complication of vesicant chemotherapy administration. Some extravasation injuries prompt litigation and the oncologist's actions, or lack of action, are scrutinized in the courtroom. This article presents advice and recommendations for treating patients who receive vesicants and includes a discussion of FDA-approved vesicant extravasation treatments and antidotes.
Professional Challenges in Cancer Genetic Testing: Who Is the Patient?
Authors: Chan-Smutko Gayun , Patel Devanshi , Shannon Kristen M. , Ryan Paula D.
Published: March 2008

In the genetic counseling setting, the health care provider can be challenged by opposing duties to members of the same family: protecting the privacy of the patient identified with a gene mutation and the ethical obligation to warn at-risk relatives. In a situation of nondisclosure between members of a family with a known disease-predisposing mutation, this type of dilemma can present in acute form for the provider who cares for different members of the family. This can hinder effective medical decision making. To minimize this effect, we recommend detailed pretest genetic counseling steps to empower the patient to communicate with their at-risk relatives their intent to pursue testing and willingness to share information. In addition, post-test counseling should reiterate the implications of a positive result for at-risk relatives and conclude with a written summary that patients can share with their family.
Post-punching behaviour of prestressed concrete flat slabs
Authors: Pinho Ramos A. , Lúcio V. J. G.
Published: March 2008

The progressive collapse of structures generally results in the loss of human lives. Experience shows that flat slab structures are very sensitive to progressive collapse, which may cause serious accidents if special detailing is not provided. The post-punching behaviour of a column-supported slab is decisive in the progressive collapse development. This work presents the experimental research carried out to study the post-punching behaviour of prestressed concrete flat slabs. Six reduced-scale prestressed concrete flat slab models were tested. The tests were carried out in two different phases. In the first phase the models were loaded up to failure by punching. Afterwards, the models were loaded again to study the post-punching behaviour changes caused by the presence of unbonded, prestressed tendons and the influences of their distance to the column.
Use of ultra-high-strength bars for seismic performance of rectangular high-strength concrete frame columns
Authors: Xiao X. , Guan F. L. , Yan S.
Published: March 2008

The application of high-strength concrete (HSC) in high-rise structures is becoming an increasingly used practice. In order to improve the ductility of HSC, many studies are conducted worldwide. In this paper, the effect of ultra-high-strength reinforcement on the seismic behaviour of HSC columns is investigated through numerical analysis and experiments. The results of the numerical analysis are compared with the experimental results. The comparison shows that the numerical analysis results agree very well with the experiments. The results also show that the flexural behaviour of the columns can be effectively improved by use of mixed ultra-high-strength steel bars with a yield strength above 1000 MPa and normal-strength steel bars for the longitudinal reinforcement. Moreover, the test also shows that the ductility of HSC columns, which are reinforced by an ultra-strength stirrup rebar, is better than that of a column which is confined by the normal reinforcement, especially in the case of high-strength concrete columns with compression strength above C60. Finally, an experiential formula for the ductility, which is related to the yield strength of ultra-high-strength steel bars, was derived on the basic of test data and numerical analysis results.
A DERIVED TRANSFER OF FUNCTIONS AND THE IMPLICIT ASSOCIATION TEST
Authors: O'Toole Catriona , Barnes‐Holmes Dermot , Smyth Sinead
Published: March 2008

Participants were trained in a series of interrelated conditional discriminations that aimed to establish four 4‐member equivalence classes (i.e., A1‐B1‐C1‐D1, A2‐B2‐C2‐D2, A3‐B3‐C3‐D3, A4‐B4‐C4‐D4). During this training, the four A stimuli (i.e., A1, A2, A3, and A4) were compounded with pictures containing positive or negative evaluative functions (A1/A2 negative & A3/A4 positive). The transfer of evaluative functions to directly and indirectly related members of the equivalence classes (i.e., B, C, and D stimuli) was measured using an Implicit Association Test (IAT). During consistent test blocks, participants were required to press the same response key for target words that were related to those A stimuli that possessed similar evaluative functions (A1/A2‐left key & A3/A4‐right key). During inconsistent test blocks, target words that were related to those A stimuli with different evaluative functions were assigned to the same response key (A1/A4‐left key & A2/A3‐right key). Results showed that all 8 participants, who passed a matching‐to‐sample equivalence test following the IAT, responded more rapidly on consistent relative to inconsistent test blocks. This typical IAT effect was not observed for those participants who did not pass the equivalence test. The results suggest that the IAT effect may arise from formally untested derived relations, and supports the argument that such relations could provide a valid behavioral model of semantic categories in natural language.
IRT‐STIMULUS CONTINGENCIES IN CHAINED SCHEDULES: IMPLICATIONS FOR THE CONCEPT OF CONDITIONED REINFORCEMENT
Authors: Bejarano Rafael , Hackenberg Timothy D.
Published: March 2008

Two experiments with pigeons investigated the effects of contingencies between interresponse times (IRTs) and the transitions between the components of 2‐ and 4‐component chained schedules (Experiments 1 and 2, respectively). The probability of component transitions varied directly with the most recent (Lag 0) IRT in some experimental conditions and with the 4th (Lag 4) IRT preceding the most recent one in others. Mean component durations were constant across conditions, so the reinforcing effect of stimulus change was dissociated from that of delay to food. IRTs were longer in the Lag‐0 than in the Lag‐4 conditions of both experiments, thus demonstrating that stimulus change functioned as a reinforcer. In the Lag‐0 conditions of Experiment 2, the Component‐1 IRTs increased more than the Component‐2 IRTs, which in turn increased more than the Component‐3 IRTs. This finding runs counter to the conditioned‐positive‐reinforcement account of chained‐schedule responding, which holds that the reinforcing effect of stimulus change should vary in strength as an inverse function of the delay to the unconditioned reinforcer at the end of the chain because conditioned reinforcement is due to first‐ or higher‐order classical conditioning. Therefore, we present other possible explanations for this effect.
A THEORY OF ATTENDING, REMEMBERING, AND REINFORCEMENT IN DELAYED MATCHING TO SAMPLE
Authors: Nevin John A. , Davison Michael , Odum Amy L. , Shahan Timothy A.
Published: March 2008

A theory of attending and reinforcement in conditional discriminations (Nevin, Davison, & Shahan, 2005) is extended to working memory in delayed matching to sample by adding terms for disruption of attending during the retention interval. Like its predecessor, the theory assumes that reinforcers and disruptors affect the independent probabilities of attending to sample and comparison stimuli in the same way as the rate of overt free‐operant responding as suggested by Nevin and Grace (2000), and that attending is translated into discriminative performance by the model of Davison and Nevin (1999). The theory accounts for the effects of sample‐stimulus discriminability and retention‐interval disruption on the levels and slopes of forgetting functions, and for the diverse relations between accuracy and sensitivity to reinforcement reported in the literature. It also accounts for the effects of reinforcer probability in multiple schedules on the levels and resistance to change of forgetting functions; for the effects of reinforcer probabilities signaled within delayed‐matching trials; and for the effects of reinforcer delay, sample duration, and intertrial‐interval duration. The model accounts for some data that have been problematic for previous theories, and makes testably different predictions of the effects of reinforcer probabilities and disruptors on forgetting functions in multiple schedules and signaled trials.
Blood blister–like aneurysms of the internal carotid artery trunk causing subarachnoid hemorrhage: treatment and outcome
Authors: Meling Torstein R. , Sorteberg Angelika , Bakke Søren J. , Slettebø Haldor , Hernesniemi Juha , Sorteberg Wilhelm
Published: March 2008

Object

The object of this study was to evaluate cases of subarachnoid hemorrhage (SAH) from ruptured blood blister–like aneurysms (BBAs) of the internal carotid artery (ICA) trunk.

Methods

The authors performed a single-center, retrospective study. Data analyzed were patient age, sex, Hunt and Hess grade, Fisher grade, time from SAH to hospitalization, aneurysm size and location, collateral capacity of the circle of Willis, time from hospitalization to aneurysm repair, type of aneurysm repair, complications, and Glasgow Outcome Scale (GOS) score at follow-up.

Results

A total of 211 patients suffered SAH from ICA aneurysms. Of these, 14 patients (6.6%) had ICA trunk BBAs; 6 men and 8 women. The median age was 47.8 years (range 29.9–67.7 years). The Hunt and Hess grade was IV or V in 7 cases, and SAH was Fisher Grade 3 + 4 in 6. All aneurysms were small (< 1 cm), without relation to vessel bifurcations, and usually located anteromedially on the ICA trunk. Three patients were treated with coil placement and 11 with clip placement. Of the 7 patients in whom the ICA was preserved, only 1 had poor outcome (GOS Score 2). In contrast, cerebral infarcts developed in all patients treated with ICA sacrifice, directly postoperatively in 2 and after delay in 5. Six patients died, 1 survived in poor condition (GOS Score 3; p < 0.001).

Conclusions

Internal carotid BBAs are rare, small, and difficult to treat endovascularly, with only 2 of 14 patients successfully treated with coil placement. The BBAs rupture easily during surgery (ruptured in 6 of 11 surgical cases). Intraoperative aneurysm rupture invariably led to ICA trap ligation. Sacrifice of the ICA within 48 hours of an SAH led to very poor outcome, even in patients with adequate collateral capacity on preoperative angiograms, probably because of vasospasm-induced compromise of the cerebral collaterals.
Microvascular decompression for trigeminal neuralgia in elderly patients
Authors: Sekula Raymond F. , Marchan Edward M. , Fletcher Lynn H. , Casey Kenneth F. , Jannetta Peter J.
Published: March 2008

Object

Although microvascular decompression (MVD) for patients with medically refractory trigeminal neuralgia (TN) is widely accepted as the treatment of choice, other “second-tier” treatments are frequently offered to elderly patients due to concerns regarding fitness for surgery. The authors sought to determine the safety and effectiveness of MVD for TN in patients older than 75 years of age.

Methods

The authors performed a retrospective review of medical records and conducted follow-up telephone interviews with the patients. The outcome data from 25 MVD operations for TN performed in 25 patients with a mean age of 79.4 years (range 75–88 years) were compared with those of a control group of 25 younger patients with a mean age of 42.3 years (range 17–50 years) who underwent MVDs during the same 30-month period from July 2000 to December 2003.

Results

Initial pain relief was achieved in 96% of the patients in both groups (p = 1.0). There were no operative deaths in either group. After an average follow-up period of 44 and 52 months, 78 and 72% of patients in the elderly and control groups, respectively, remained pain free without medication (p = 0.74).

Conclusions

Microvascular decompression is an effective treatment for elderly patients with TN. The authors' experience suggests that the rate of complications and death after MVD for TN in elderly patients is no different from the rate in younger patients.
Long-term recurrence and mortality after surgery and adjuvant radiotherapy for nonfunctional pituitary adenomas
Authors: Chang Edward F. , Zada Gabriel , Kim Sang , Lamborn Kathleen R. , Quinones-Hinojosa Alfredo , Tyrrell J. Blake , Wilson Charles B. , Kunwar Sandeep
Published: March 2008

Object

Long-term outcomes following surgery for nonfunctional pituitary adenomas (NFPAs) are unclear. The role of adjuvant radiation therapy is therefore controversial because it is associated with higher tumor control but also carries known long-term morbidity. The authors' aim was to determine predictors of recurrence and overall survival and to define patient subgroups that may benefit from radiotherapy.

Methods

The authors performed a retrospective cohort analysis of 663 patients who underwent surgery between 1975 and 1995 for treatment of primary NFPAs. The main outcome measures were disease progression after surgery, defined by clinical and/or imaging criteria, and all-cause mortality.

Results

Over a median clinical follow-up of 8.4 years, there were 64 (9.7%) recurrences after treatment, with a median time to recurrence of 5.6 years. The 5-, 10-, and 15-year recurrence-free probabilities were 0.93, 0.87, and 0.81, respectively. Multivariate Cox proportional hazard regression analysis identified the following predictors as associated with increased recurrence: cavernous sinus invasion (hazard ratio [HR] 3.6, 95% confidence interval [CI] 1.5–6.4; p < 0.001) and subtotal resection (STR) without radiotherapy (HR 3.6, 95% CI 1.4–14; p = 0.01). Using time-to-event estimates to adjust for differences in follow-up between groups, radiotherapy was found to reduce tumor recurrence in only those patients who received an STR (p < 0.001, log-rank test) but not gross-total resection (GTR; p = 0.63, log-rank test). Median follow-up for overall survival was 14.0 years. The 5-, 10-, 15- and 20-year overall survival estimates were 0.91, 0.81, 0.69, and 0.55, respectively. Within the study cohort and in age- and sex-adjusted comparison with the general US population, increased relative mortality was observed in patients who underwent radiotherapy or STR.

Conclusions

Cavernous sinus invasion is an important prognostic variable for long-term control of NFPAs. Radiotherapy results in long-term tumor control for patients who undergo STR but does not affect recurrence rates and may increase the risk of death after GTR. Given the risks associated with radiotherapy, there is no role for its routine application in patients who have undergone GTR of their NFPA. In all patients, long-term monitoring is required.
The claustrum and its projection system in the human brain: a microsurgical and tractographic anatomical study
Authors: Fernández-Miranda Juan C. , Rhoton Albert L. , Kakizawa Yukinari , Choi Chanyoung , Álvarez-Linera Juan
Published: March 2008

Object

The goal in this study was to examine the microsurgical and tractographic anatomy of the claustrum and its projection fibers, and to analyze the functional and surgical implications of the findings.

Methods

Fifteen formalin-fixed human brain hemispheres were dissected using the Klingler fiber dissection technique, with the aid of an operating microscope at × 6–40 magnification. Magnetic resonance imaging studies of 5 normal brains were analyzed using diffusion tensor (DT) imaging–based tractography software.

Results

Both the claustrum and external capsule have 2 parts: dorsal and ventral. The dorsal part of the external capsule is mainly composed of the claustrocortical fibers that converge into the gray matter of the dorsal claustrum. Results of the tractography studies coincided with the fiber dissection findings and showed that the claustrocortical fibers connect the claustrum with the superior frontal, precentral, postcentral, and posterior parietal cortices, and are topographically organized. The ventral part of the external capsule is formed by the uncinate and inferior occipitofrontal fascicles, which traverse the ventral part of the claustrum, connecting the orbitofrontal and prefrontal cortex with the amygdaloid, temporal, and occipital cortices. The relationship between the insular surface and the underlying fiber tracts, and between the medial lower surface of the claustrum and the lateral lenticulostriate arteries is described.

Conclusions

The combination of the fiber dissection technique and DT imaging–based tractography supports the presence of the claustrocortical system as an integrative network in humans and offers the potential to aid in understanding the diffusion of gliomas in the insula and other areas of the brain.
Low-grade fibromyxoid sarcoma of intracranial origin
Authors: Saito Ryuta , Kumabe Toshihiro , Watanabe Mika , Jokura Hidefumi , Shibuya Makoto , Nakazato Yoichi , Tominaga Teiji
Published: March 2008

✓The authors report on a 21-year-old man who presented with a low-grade fibromyxoid sarcoma primarily located in the right parietal lobe with diffuse infiltration. The low-grade fibromyxoid sarcoma is a rare sarcoma of the deep soft tissue that is characterized as an indolent but metastasizing soft-tissue neoplasm with a deceptively benign histological appearance. Only one case of intracranial origin has been previously reported in the literature. A high rate of local recurrence and eventual metastasis has been demonstrated for this tumor in deep soft tissue. Similarly, the patient in the present case suffered recurrence 6 times; he underwent treatment by surgical removal 4 times, Gamma Knife surgery twice, and local radiation therapy once during the 7-year follow-up period. The tumor is still under control without any evidence of extracranial metastasis. To the authors' knowledge, this is the first case report that discusses the clinical course of this rare disease in detail.
Pioneering Turkish neurosurgeon Hami Dilek and the traces of Harvey Cushing's legacy in his work
Authors: Elmaci Ilhan , Balak Naci
Published: March 2008

✓ Hami Dilek trained in neurosurgery under Clovis Vincent and Thierry de Martel, pioneers of French neurosurgery who ranked among Harvey Cushing's most loyal admirers. Taking cues from Cushing and the giants of French neurosurgery, Dilek became the first surgeon to practice neurosurgery regularly in Turkey during the 1930s. In 1949, Dilek founded the first independent Turkish department of neurosurgery in Istanbul, and in 1951 he initiated resident training in neurosurgery. Both Cushing and Dilek started out as general surgeons and then became fascinated by the brain and spine. Also, they both single-handedly developed a new specialty where one did not exist before. Further similarities between Dilek and Cushing are also revealed in Dilek's delightful surgical and anatomical drawings. Dilek played an important role in the establishment and development of modern Turkish neurosurgery, and his life story highlights the fact that Cushing's legacy strongly influenced Turkish neurosurgery in the first half of the 20th century.
Recurrent intracerebral hemorrhage from a cerebral arteriovenous malformation undetected by repeated noninvasive neuroimaging in a 4-year-old boy
Authors: Jordan Lori C. , Jallo George I. , Gailloud Philippe
Published: March 2008

✓ The authors report the case of a 4-year-old boy with a spontaneous intracerebral hemorrhage (ICH) related to an arteriovenous malformation (AVM) that was not found with good-quality magnetic resonance (MR) imaging and MR angiography. Both modalities were used serially in the acute phase and at 2 and 7 months of follow-up. Digital subtraction angiography identified the peripheral AVM when the patient experienced rehemorrhaging 1 year after his initial presentation. This case illustrates the need for a complete diagnostic evaluation including conventional angiography in cases of idiopathic ICH in children.
Internal carotid artery dissection following wooden arrow injury to the posterior pharynx
Authors: Lubarsky Michael , Helmer Robert , Knight Charles , Mullins Mark E.
Published: March 2008

✓ In this report the authors describe a case of internal carotid artery (ICA) dissection following a blunt posterior pharynx injury and review current literature on the identification and treatment of such disorders. An ICA dissection developed in a 6-year-old boy who had suffered blunt injury to the posterior pharynx and who was followed up via computed tomography (CT) angiography and clinic visits for 6 months. The ICA dissection healed with pseudoaneurysm development and was treated with anticoagulation therapy.

The authors searched the January 1996 through March 2007 MEDLINE database by using the Ovid search engine. They requested all English-language articles with the term “carotid dissection.” Reference lists from these articles were retrieved and searched for additional relevant sources. The authors found that given its availability and speed of acquisition, CT angiography typically is the preferred initial diagnostic method. Magnetic resonance angiography is usually recommended for follow-up examination especially in pediatric cases. According to the available literature, the current preferred treatment for ICA dissection is anticoagulation.
Pediatric Neurosurgery in a Non-Academic City Hospital
Authors: Grabb Paul
Published: March 2008

Introduction

Creation of a pediatric neurosurgical service in the community has challenges unique from establishing such a service in an academic setting. I outline the challenges in creating a pediatric neurosurgical service within a large city-owned hospital. Critical equipment system-related and man-power issues were identified.

Methods

The NACHRI designated children's hospital (Memorial Hospital for Children) serves southern Colorado. Coverage was not provided by the community neurosurgeons. Therefore, children requiring neurosurgical management traveled to Denver or elsewhere. A pediatric neurosurgeon was hired to establish a clinical service in 2004.

Results

Equipment such as endoscopy, frameless stereotaxy, ICP monitors, and shunt components were obtained easily. Familiarizing the OR/ICU staff with the equipment, however, required months as this technology was rarely utilized by the other surgeons. System-related concerns were many and mostly educational involving the ER, PICU, NICU, and floor. Identifying anesthesiologists with pediatric expertise and desire was critical. Unexpected system-related benefits compared to a university-based Children's Hospital were lack of resistance for imaging studies requiring sedation or invasive studies (angiography), outstanding intraoperative support for spinal instrumentation cases, very rapid transport to OR of trauma patients, and speed of anesthesia. Man-power issues of no cross-coverage remain problematic primarily because of insurance premium increases to provide pediatric coverage. Any increased burden by nonresidents is offset by the support of other specialties (emergency room physicians, intensivists, and trauma surgeons). Physician extenders require a large amount of education and oversight before reducing clinical burden.

Conclusion

Creating a pediatric neurosurgical service within a community hospital requires financial support from the hospital, a system capable of and willing to care for children with complex problems and other specialties, and physician extenders competent to assist with the service. The medicolegal/insurance landscape hinders more complete coverage within our system. A tremendous educational effort is required to establish and maintain a safe and functional service.
Technical Aspects of Ventriculogallbladder Shunts: The Surgical Team Preoperative Assessment. Operative Intervention and Postoperative Assessment: A Clinical Report
Authors: James Hector , Aldana Philipp , Postlethwait Richard
Published: March 2008

Introduction

Ventriculogallbladder shunts (VGBSs) have been employed when there is a contraindication for intraperitoneal shunt placement or when CSF is no longer absorbed by the peritoneum. We report our clinical experience with 19 patients (1986–2006) with particular emphasis on perioperative management.

Methods

In 18 patients VGBS placement was indicated because of failure of abdominal absorption of CSF and in one patient due to multiple intraperitoneal general surgery operative interventions. An absolute preoperative requirement is documenting the presence and status of the gallbladder by ultrasonography or CT. The proximal portion was similar to a ventriculoperitoneal shunt with emphasis in a proximal one-way valve; the distal end was performed by open laparotomy to adequately anchor the distal end to the distal pole of the gallbladder wall and verify the length inside the gallbladder. Additional redundant distal shunt tubing was placed in the abdomen, allowing for subsequent patient growth. Prior to hospital discharge, the gallbladder status was evaluated by ultrasound to document function.

Results

The following highlights the importance of the preoperative assessment: one patient had congenital agenesis of the gallbladder. One patient had “sludge” formation on preoperative ultrasound that in the immediate postoperative period developed an obstruction of the common duct that required shunt removal. Two patients had shunt infections (S. epidermis, H. influenzae) and 15 patients had successful long-term shunt function.

Conclusion

We conclude that VGBSs should be considered an important tool in the armamentarium of pediatric neurosurgery.
Tissue Engineering: Growing Skull with In Situ Osteogenesis
Authors: Flannery Ann Marie
Published: March 2008

Introduction

Acquired skull defects are common as a result of trauma infection and calvarial expansion among other causes. The techniques available to repair these defects have included a variety of foreign body implants or bone grafting from proximal or distant sites. Tissue engineering using bone morphogenetic protein (rBMP) and an absorbable mesh scaffold offers a unique opportunity to fill defects with in situ osteogenesis.

Methods

Bony calvarial defects in 19 children ranging in age from 11 months to 15 years were repaired using rBMP and a collagen scaffold plus a synthetic hydroxyapatite ceramic in a granular or matrix form. The construct is held with poly D,L-lactide acid resorbable mesh. The skull defects were a result of trauma (n = 5) craniotomy for tumor (n = 2), congenital absence (n = 1), infection (n = 4), and calvarial expansion for synostosis (n = 7). The reconstruction technique varied with the size and geometry of the defect. The defects repaired ranged from 10 to 60 cm2. Results of the repair were judged by physical exam and 3D computed tomography.

Results

In 18 patients followed for at least 6 months, the calvarium was completely ossified in 15 cases and had a small residual defect (2 cm2) in 3 from early in the series. Two surgeries were required to completely reconstruct a bifrontal bone flap.

Conclusion

BMP shows promise for repairing significant calvarial defects by promoting the growth of the patient's own bone in situ osteogenesis, thereby avoiding the need for foreign body implants or bone grafts from other sites.
Timing of surgery in cauda equina syndrome with urinary retention: meta-analysis of observational studies
Authors: DeLong W. Bradford , Polissar Nayak , Neradilek Blažej
Published: March 2008

Object

The authors performed exploratory meta-analyses of observational cohort studies, evidence level III, examining whether earlier surgery makes a difference in outcome in terms of urinary function once cauda equina syndrome (CES) from a herniated lumbar disc has progressed to urinary retention (CESR).

Methods

Literature search identified 27 studies of CESR patients with clear definition of surgical timing. Relative risk (RR) could not be calculated in 11 studies, leaving 16 for meta-analysis. Urinary retention related to surgical timing at 5 breakpoints: 12, 24, 36, 48, or 72 hours. Urinary outcome was classified as Normal, Fair, or Poor. Meta-analysis was performed for “Event = Fair/Poor” or “Event = Poor.” Eight studies allowed separation into CESR and incomplete CES (CESI), and 5 of these had enough data for meta-analysis to compare CESR and CESI. A random effects meta-analysis model was used because of heterogeneity across the studies. A best-evidence synthesis was performed for the 4 largest studies that had 24- and 48-hour breakpoints.

Results

For “Event = Fair/Poor,” meta-analyses using the 5 breakpoints predicted a more likely Fair/Poor outcome for later surgery (RR range 1.77–2.19). The RR for later timing of surgery was statistically significant for 24-and 72-hour breakpoints and was elevated but not statistically significant for the other 3. For “Event = Poor,” the RR range was 1.09–5.82, statistically significant for the 36 hour breakpoint only. Meta-analysis comparing CESR patients with CESI patients predicted a Fair/Poor result for CESR (RR 2.58, 95% confidence interval 0.59–11.31). The best-evidence synthesis did not disclose reasons for differences in the results of the 4 studies.

Conclusions

This study supports early surgery for CES and indicates that CESR and CESI cases should not be analyzed together.
Anatomical relationship of the internal carotid artery to C-1: clinical implications for screw fixation of the atlas
Authors: Hoh Daniel J. , Maya Marcel , Jung Alexander , Ponrartana Skorn , Lauryssen Carl L.
Published: March 2008

Object

Various C1–2 instrumentation techniques have been developed to treat atlantoaxial instability. Screw fixation of C1–2 poses a risk of injury to the vertebral artery and internal carotid artery (ICA). Injury to the ICA caused by C-1 screws is extremely rare, but has been described. To characterize this risk, the authors studied the anatomical relationship of the ICA to the lateral mass of C-1.

Methods

The authors studied 100 patients who had undergone computed tomography scanning and magnetic resonance imaging of the neck to assess the position of the ICA in association with the C-1 lateral mass. Each ICA was classified into 1 of the following 4 zones: Zone 1 (medial to lateral mass), Zone 2 (medial half of lateral mass), Zone 3 (lateral half of lateral mass), and Zone 4 (lateral to lateral mass). For patients with an ICA ventral to the lateral mass, the shortest distance between the ICA and lateral mass was measured to determine the margin of error with an overpenetrated bicortical screw.

Results

Of the 100 patients, 58% had a left ICA in Zones 2 and 3 with a mean distance from the anterior cortex of 3.5 ± 1.5 mm (± standard deviation), and 74% had a right ICA in Zones 2 and 3 with a mean distance from the anterior cortex of 3.9 ± 1.6 mm. Both ICAs anterior to the lateral mass were noted in 47% of patients, and 84% had ≥ 1 ICA anterior to the lateral mass. When the ICA was anterior to the lateral mass, it was more commonly in the lateral half (left ICA in 91% and right ICA in 92%). The left ICA was in Zone 1 in 1% and Zone 4 in 41%. The right ICA was in Zone 1 in 1% and Zone 4 in 25%.

Conclusions

A high percentage of patients demonstrate an ICA directly ventral to the C-1 lateral mass, which poses a risk of ICA injury caused by an overpenetrated bicortical screw.