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Papers by Matthew Griffith

Journal of Physical Chemistry C, 2011

A significant improvement in the photovoltaic performance of porphyrin-sensitized TiO 2 solar cel... more A significant improvement in the photovoltaic performance of porphyrin-sensitized TiO 2 solar cells under white light illumination is reported. The most significant improvement occurs within the first hour of light exposure and is irreversible within at least the studied 3-month period. Heat treatment in the dark produced only moderate performance improvement, whereas light treatment using a UV long-pass filter (>475 nm) led to an improvement similar to that obtained with the full simulated AM 1.5 spectrum, suggesting that the effect is linked to the photoexcitation of the porphyrin dye molecules. Light exposure resulted in simultaneous improvements in the short-circuit current (J sc ), the open-circuit voltage (V oc ), and the fill factor (FF). The J sc improvement is attributed to better charge injection demonstrated by thin-film APCE measurements. Photovoltage decay measurements showed a factor of 2-3 increase in the electron lifetime after light exposure, accompanied by a comparable decrease in the electron diffusion coefficient. The improved electron lifetime combined with the increased J sc resulted in increased electron densities under open-circuit conditions, leading to improved V oc . Electrochemical impedance measurements showed a reduced charge-transfer resistance for I 3 reduction at the Pt counter electrode, which is thought to be responsible for the increased filling factor. Furthermore, ATR-FTIR and X-ray reflectometry measurements indicated no significant change in the dye layer morphology after light exposure. An alternative mechanism involving the photogeneration of electronic states within the band gap of TiO 2 leading to improved injection, slower electron transport, and improved electron lifetime is discussed.

Curr Opin Infect Dis, 2006

Leptospirosis is an important but often overlooked zoonotic disease that can cause significant mo... more Leptospirosis is an important but often overlooked zoonotic disease that can cause significant morbidity and mortality. The optimal antimicrobial treatment for this disease has not been established. This review summarizes the most recent literature pertaining to the use of antimicrobial agents in the treatment of leptospirosis. Leptospira are highly susceptible to a wide variety of antimicrobials in vitro. Despite this, it is not clear what the best choice of antimicrobial agents is for human disease. Based on the best available literature, the current choices of treatment for leptospirosis include penicillin, doxycycline, cefotaxime, ceftriaxone and azithromycin. Penicillin has long been considered the treatment of choice. Doxycycline is a reasonable alternative, but concerns exist regarding its use in all patients. Recent trials have demonstrated that cefotaxime and ceftriaxone are also acceptable agents. For a variety of reasons, these may be the preferred agents at this time. Azithromycin appears promising for the treatment of less severe disease. Another option for treating leptospirosis is the fluoroquinolone antimicrobials, although adequate human trials are lacking to fully support their use. Leptospirosis is an important cause of morbidity and mortality worldwide. Despite this, the optimal treatment is not fully defined.

Clinical Orthopaedics and Related Research, Oct 1, 2007

Staphylococcus aureus infection is a serious complication in patients receiving orthopaedic impla... more Staphylococcus aureus infection is a serious complication in patients receiving orthopaedic implants. Treatment with antibiotic-loaded cements can deliver high local concentrations and reduce toxic side effects associated with systemic antibiotic administration, but polymethylmethacrylate cement is nondegradable and may necessitate additional surgery for removal. Previous studies provide support for hydroxyapatite as a biodegradable carrier, but consensus has not been achieved. We hypothesized vancomycin-loaded hydroxyapatite was superior to vancomycin-loaded polymethylmethacrylate in reducing the number of bacterial colony-forming units in the setting of osteomyelitis. Osteomyelitis was induced in rats using an established model. Animals then were randomly assigned to a control group (no antibiotics), a group treated with vancomycin-loaded polymethylmethacry-late, and two groups treated with hydroxyapatite loaded with either low-dose or high-dose vancomycin. After 6 weeks we compared the number of colony-forming units per gram of harvested bone between groups. Vancomycin-loaded hydroxyapatite was inferior to vancomycin-loaded polymethylmethacrylate in reducing the number of bacterial colony-forming units and vancomycin-loaded polymethylmethacry-late was superior to the control group. We observed no difference between low- and high-dose vancomycin-loaded hydroxyapatite groups. The poor handling properties of hydroxyapatite paste may explain these findings. Based on these results, a hydroxyapatite carrier cannot be recommended for the treatment of osteomyelitis.

Solar Energy Materials and Solar Cells, 2016

Military Medicine, Sep 1, 2009

IEEE Journal of Selected Topics in Quantum Electronics, 2015

The Journal of Physical Chemistry C, 2015

RSC Adv., 2015

In this study, binder-free TiO 2 colloidal pastes have been prepared using a variety of heterocyc... more In this study, binder-free TiO 2 colloidal pastes have been prepared using a variety of heterocyclic bases with diverse characteristics to produce robust photoanodes for dye-sensitized solar cells (DSSC) from a single cast film thickness of 5 micron. The influence of the base on the electrode structure and film morphology, including its electron donor characteristics are investigated after low temperature thermal treatment and high temperature sintering. The results show that quinoline in the TiO 2 paste is retained within the electrode structure in comparison to piperidine and pyridine after a short thermal treatment of 150 C for 15 minutes. The presence of organic additives with p-conjugation in the photoanode enhances both electron injection efficiency and charge carrier lifetime resulting in higher J sc and V oc . This formulation in combination with low temperature processing yields an energy conversion efficiency of over 5% in DSSC devices. In devices where high temperature sintering is permitted, the performance of TiO 2 electrodes converges towards an efficiency of over 6%, irrespective of the organic additive within the paste. This formulation offers a high degree of versatility in casting electrodes onto polymer, glass or metal foil substrates from a single source of TiO 2 paste, for the many variants of low-cost solar cells.

Introduction: Throughout the field of orthopedic surgery, there has been a trend toward using sma... more Introduction: Throughout the field of orthopedic surgery, there has been a trend toward using smaller incisions and implants that preserve as much normal anatomy as possible. The use of bone sparing technology, such as partial and full surface replacements of the humeral head, while attractive in younger patients, does not allow the best exposure for proper glenoid replacement. Additionally, there are other situations when the use of surface replacements is contraindicated. There are also patients with an existing total elbow replacement or a humeral malunion or deformity in which a traditional long-stem component would not fit. For these reasons, a mini-stem humeral component for total shoulder arthroplasty was developed. In this study, we hypothesized that total shoulder replacement using the mini-stem humeral component could provide low complication rates and good to excellent results, as measured by postoperative Constant-Murley and UCLA shoulder scores at minimum 2 years postoperatively. Materials and Methods: This was a retrospective review of the first 49 mini-stem shoulder replacements (47 patients) for primary osteoarthritis. There were 26 male and 23 female patients. UCLA Shoulder Score and Constant Murley Scores were obtained on all patients at a minimum of 2 years postoperatively (average 29 months; range 24-43 months). Radiographs were interpreted by a musculoskeletal radiologist. Intraoperative blood loss was documented as was postoperative pain using a visual analog pain scale. Results: Patients experienced over 90% good to excellent results at minimum 2 year follow up. ROM improved significantly in all parameters. Postoperative UCLA scores at final follow up averaged 27.5 while Constant-Murley scores averaged 91. Small lucent lines (<1 mm) were noted in 11 patients. Five of 49 stems were placed in varus but the postoperative result was not affected in any of these patients. One patient suffered an acute subscapularis rupture that required repair. Conclusions: This is the first report to document the efficacy of mini-stemmed humeral components used during total shoulder arthroplasty. Our study group showed good to excellent results as well as improvement in range of motion at minimum 2-year follow-up. The results presented in this study are comparable to previous outcomes achieved with conventional length humeral components, and suggest that mini-stem humeral components are an effective option for total shoulder arthroplasty.

The Journal of Physical Chemistry C, 2011

The Journal of Physical Chemistry C, 2013

The origin of simultaneous improvements in the short-circuit current density (J sc ) and open-cir... more The origin of simultaneous improvements in the short-circuit current density (J sc ) and open-circuit voltage (V oc ) of porphyrin dye-sensitized TiO 2 solar cells following white light illumination was studied by systematic variation of several different device parameters. Reduction of the dye surface loading resulted in greater relative performance enhancements, suggesting open space at the TiO 2 surface expedites the process. Variation of the electrolyte composition and subsequent analysis of the conduction band potential shifts suggested that a light-induced replacement of surface-adsorbed lithium (Li + ) ions with dimethylpropylimidazolium (DMPIm + ) ions was responsible for an increased electron lifetime by decreasing the recombination with the redox mediator. Variation of the solvent viscosity was found to affect the illumination time required to generate increased performance, while similar performance enhancements were not replicated by application of negative bias under dark conditions, indicating the light exposure effect was initiated by formation of dye cation molecules following photoexcitation. The substituents and linker group on the porphyrin chromophore were both varied, with light exposure producing increased electron lifetime and V oc for all dyes; however, increased J sc values were only measured for dyes containing binding moieties with multiple carboxylic acids. It was proposed that the initial injection limitation and/or fast recombination process in these dyes arises from the presence of lithium at the surface, and the improved injection and/or retardation of fast recombination after light exposure is caused by the Li + removal by cation exchange under illumination.

Osteoarthritis and Cartilage, 2007

Purpose: Histology plays a critical role in cartilage repair research. However, routine manual hi... more Purpose: Histology plays a critical role in cartilage repair research. However, routine manual histoprocessing for orthopaedic tissues remains laborious, time-consuming and requires toxic chemicals. The current study investigated the ability of microwave technology (Milestone) to process osteochondral and synovial samples, and compared histological quality and reproducibility to standard manual histoprocessing. Methods and Materials: 8 rabbit femoral articular cartilage and patellar synovial tissue samples, and 3 human osteochondral samples were samples were sectioned to 5 µm and either stained with Safranin-O/Fast Green or immunostained for collagen type II. Synovial sections were stained with H&E. Results: Microwave processing substantially decreased processing time from 46 to 3.25 hours for cartilage, and 8 to 3.25 hours for synovial tissue, without the use of toxic xylene and toluene. Both methods produced high quality tissue sections that underwent minimal shrinkage, contained very few artifacts, and did not exhibit swelling of connective tissue characteristics and the subchondral bone contained osteoclasts with few morphological alterations. Cartilage GAG staining intensity observed with Safranin-O was reproducible for both histoprocessing methods, as was collagen type II staining. However, only microwave processing preserved bone marrow structures and allowed differentiation between marrow cell types. Conclusions: Microwave histoprocessing consistently produced high quality, reproducible and equivalent histological results when compared with routine manual histoprocessing for both osteochondral and synovial through much shorter histoprocessing times in a safer environment.

Langmuir, 2011

Langmuir ARTICLE thickness. Determination of adsorption orientations and packing densities from t... more Langmuir ARTICLE thickness. Determination of adsorption orientations and packing densities from the measured dye thicknesses exhibits good agreement with literature values.

The Journal of Trauma: Injury, Infection, and Critical Care, 2010

We hypothesized that near-infrared spectroscopy (NIRS)-derived tissue oxygenation saturation (StO... more We hypothesized that near-infrared spectroscopy (NIRS)-derived tissue oxygenation saturation (StO2) could assist in identifying shock in casualties arriving to a combat support hospital and predict the need for life-saving interventions (LSIs) and blood transfusions. We performed a prospective observational trial at a single US Army combat support hospital in Iraq from August to December 2007. Arriving casualties had NIRS-derived StO2 recorded in the emergency department. Minimum (StO2 min) and initial 2-minute averaged StO2 and tissue hemoglobin index readings were used as end points. Outcomes measured were requirement for LSIs, any blood transfusion, massive transfusion (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;10 units in 24 hours), and early mortality. The data were subjected to univariate and multivariate logistic regression modeling. Of the 147 combat casualties enrolled in the trial, 72 (49%) required an LSI, 42 (29%) required blood transfusion, and 10 (7%) required massive transfusion. On multivariate logistic regression analysis of the whole study group, systolic blood pressure (SBP), international normalized ratio, tissue hemoglobin index, and hematocrit predicted blood transfusion with an area under the curve of 0.90 (0.84-0.96), with a confidence interval of 95%. When just the group with an SBP &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;90 was analyzed, independent predictors of patients requiring blood transfusion on logistic regression analysis were StO2 min (odds ratio of 1.35) and hematocrit (odds ratio of 2.66) for an area under the curve of 0.84 (0.76-0.92). NIRS-derived StO2 obtained on arrival predicts the need for blood transfusion in casualties who initially seem to be hemodynamically stable (SBP &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;90). Further study of this technology for use in the resuscitation of trauma patients is warranted.

Journal of the American College of Surgeons, 2008

Infection Control and Hospital Epidemiology, 2007

Skin carriage of Acinetobacter calcoaceticus-baumannii complex was not detected among a represent... more Skin carriage of Acinetobacter calcoaceticus-baumannii complex was not detected among a representative sample of 102 US Army soldiers stationed in Iraq. This observation refutes the hypothesis that preinjury skin carriage serves as the reservoir for the Acinetobacter infections seen in US military combat casualties. Control Hosp Epidemiol 2007; 28:720-722 Acinetobacter calcoaceticus-baumannii complex is an important cause of nosocomial infection worldwide. The current increase in multidrug-resistant A. calcoaceticus-baumannii complex infections seen in US military hospitals that serve soldiers wounded in Iraq is well described, although the source of this outbreak remains obscure. 2,3 We previously hypothesized that skin carriage of A. calcoaceticus-baumannii complex prior to injury may serve as a source for these infections. 4 This hypothesis is supported by several reports that describe skin carriage of Acinetobacter species in various populations, including US Army trainees. 4-7 That aside, rates of skin carriage can vary depending on climate and geography, making it unclear whether previous reports could be generalized to a population of US Army soldiers currently in Iraq. In addition, it is not known how isolates recovered from the skin of soldiers in Iraq, if present, might be genetically related to isolates recovered from other populations or to isolates recovered from injured service members. We undertook this study to determine whether skin carriage of A. calcoaceticus-baumannii complex is seen among healthy US Army soldiers currently stationed in Iraq.

Infection Control and Hospital Epidemiology, 2008

A retrospective review of hospital records for Acinetobacter baumannii infection at a US Army com... more A retrospective review of hospital records for Acinetobacter baumannii infection at a US Army combat support hospital revealed a monthly infection rate ranging from 20.5 to 0 cases per 1,000 patients admitted. The rate correlated with the mean census of host-nation patients in the intensive care unit, the mean census of host-nation patients on the wards, and length of stay in the intensive care unit.